Tek 2467B Erratic Intensity controls


peter bunge
 

My Tek 2467B has just started acting up. The Intensity and Readout Intensity controls suddenly started to be erratic. The voltages to U650 sequencer are delayed by several seconds but can be set to useable settings, however if changed the trace and/or readouts can suddenly vanish. If slowly adjusted to normal intensity and left alone the scope behaves indefinitely (not a timeout problem).

I have the service manual for the 2465 but have not been able to find one for the 2467B. Does anyone have one?

The Intensity pot voltages from the 2467B are different from the 2465 and the 2465 manual.
Intensity ccw 0V to 1.365V cw (2467B) ccw 0V to 4.55V cw (2465)
Readout Intensity ccw 1.365V to -1.252V cw (2467B) ccw -5V to +5V cw (2465)
I searched this forum and apparently the manual and the 2465 that I have has the intensity pots wired to the U650. My 2467B is wired to the CPU and drives U650 from DACs?

The 2467B has a small vertically mounted board near the U650 that I suspect has something to do with the Intensity and possibly the timed turn off that the 2465 does not have.

I suspect either U650 or the NOVRAM battery. I could replace U650 with a 155 0244 00 from a 2465 but the 2467 is 155 0244 01 and I suspect they may not be the same because of the timed Bright-eye control. Are they interchangeable?

I saw in the forum something else to check: “Did you try cleaning the contacts on the old U950 and re-insert it? My 2467 was all kinds of glitchy and twichy, misbehaving in all kinds of ways until I cleaned and re-seated the hybrids”.
I am reluctant to disturb this component and cause another problem.

Any suggestions?
PeterB


peter bunge
 

I just found pdf service manuals from Artekmedia and Didier Juges
confirming where the Intensity controls connect.
I would like to buy a printed original manual.
What would delay the voltages to pins 22 & 23 of U650? Can U650 do that and
yet other controls work (position etc)?

On Fri, Nov 29, 2019 at 10:23 AM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

My Tek 2467B has just started acting up. The Intensity and Readout
Intensity controls suddenly started to be erratic. The voltages to U650
sequencer are delayed by several seconds but can be set to useable
settings, however if changed the trace and/or readouts can suddenly vanish.
If slowly adjusted to normal intensity and left alone the scope behaves
indefinitely (not a timeout problem).

I have the service manual for the 2465 but have not been able to find one
for the 2467B. Does anyone have one?

The Intensity pot voltages from the 2467B are different from the 2465 and
the 2465 manual.
Intensity ccw 0V to 1.365V cw (2467B)
ccw 0V to 4.55V cw (2465)
Readout Intensity ccw 1.365V to -1.252V cw (2467B) ccw -5V to
+5V cw (2465)
I searched this forum and apparently the manual and the 2465 that I have
has the intensity pots wired to the U650. My 2467B is wired to the CPU and
drives U650 from DACs?

The 2467B has a small vertically mounted board near the U650 that I
suspect has something to do with the Intensity and possibly the timed turn
off that the 2465 does not have.

I suspect either U650 or the NOVRAM battery. I could replace U650 with a
155 0244 00 from a 2465 but the 2467 is 155 0244 01 and I suspect they may
not be the same because of the timed Bright-eye control. Are they
interchangeable?

I saw in the forum something else to check: “Did you try cleaning the
contacts on the old U950 and re-insert it? My 2467 was all kinds of glitchy
and twichy, misbehaving in all kinds of ways until I cleaned and re-seated
the hybrids”.
I am reluctant to disturb this component and cause another problem.

Any suggestions?
PeterB




peter bunge
 

Very confusing. The pot voltages are shown on sheet 5 going to sheet 2 into
the analog mux U2510, then through a discriminator? U2510 to a digital mux
U2220. It is not shown going to an ADC so how does the CPU know what the
values are?
Jumping to the O/P side shown on sheet 2: the O/P of DAC U2101 goes
through analog mux U2530 to amplifiers U2630 then back in through sheet 5
to pins 22 & 23 of the sequencer U650.

Where and what is U950 referred to in the forum to check and clean its
contacts?



On Fri, Nov 29, 2019 at 11:30 AM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

I just found pdf service manuals from Artekmedia and Didier Juges
confirming where the Intensity controls connect.
I would like to buy a printed original manual.
What would delay the voltages to pins 22 & 23 of U650? Can U650 do that and
yet other controls work (position etc)?

On Fri, Nov 29, 2019 at 10:23 AM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

My Tek 2467B has just started acting up. The Intensity and Readout
Intensity controls suddenly started to be erratic. The voltages to U650
sequencer are delayed by several seconds but can be set to useable
settings, however if changed the trace and/or readouts can suddenly
vanish.
If slowly adjusted to normal intensity and left alone the scope behaves
indefinitely (not a timeout problem).

I have the service manual for the 2465 but have not been able to find one
for the 2467B. Does anyone have one?

The Intensity pot voltages from the 2467B are different from the 2465 and
the 2465 manual.
Intensity ccw 0V to 1.365V cw (2467B)
ccw 0V to 4.55V cw (2465)
Readout Intensity ccw 1.365V to -1.252V cw (2467B) ccw -5V
to
+5V cw (2465)
I searched this forum and apparently the manual and the 2465 that I have
has the intensity pots wired to the U650. My 2467B is wired to the CPU
and
drives U650 from DACs?

The 2467B has a small vertically mounted board near the U650 that I
suspect has something to do with the Intensity and possibly the timed
turn
off that the 2465 does not have.

I suspect either U650 or the NOVRAM battery. I could replace U650 with a
155 0244 00 from a 2465 but the 2467 is 155 0244 01 and I suspect they
may
not be the same because of the timed Bright-eye control. Are they
interchangeable?

I saw in the forum something else to check: “Did you try cleaning the
contacts on the old U950 and re-insert it? My 2467 was all kinds of
glitchy
and twichy, misbehaving in all kinds of ways until I cleaned and
re-seated
the hybrids”.
I am reluctant to disturb this component and cause another problem.

Any suggestions?
PeterB






Chuck Harris <cfharris@...>
 

Hi Peter,

The 2465 creates an ADC function by using the DAC in concert with
MUX's, Sample-and-hold cells, and the trigger hybrid.

The CPU sets up the Mux to connect the DAC, and a sample and hold
gate to drive the DC trigger threshold input of the trigger hybrid.

The CPU adjusts the trigger threshold until the trigger hybrid just
switches from being less than to being more than the voltage being
measured when the CPU increments the DAC one count.

Tricky, but it was cheap and reliable for the times.

I'm not sure what you mean by a discriminator.

-Chuck Harris

peter bunge wrote:

Very confusing. The pot voltages are shown on sheet 5 going to sheet 2 into
the analog mux U2510, then through a discriminator? U2510 to a digital mux
U2220. It is not shown going to an ADC so how does the CPU know what the
values are?
Jumping to the O/P side shown on sheet 2: the O/P of DAC U2101 goes
through analog mux U2530 to amplifiers U2630 then back in through sheet 5
to pins 22 & 23 of the sequencer U650.

Where and what is U950 referred to in the forum to check and clean its
contacts?



On Fri, Nov 29, 2019 at 11:30 AM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

I just found pdf service manuals from Artekmedia and Didier Juges
confirming where the Intensity controls connect.
I would like to buy a printed original manual.
What would delay the voltages to pins 22 & 23 of U650? Can U650 do that and
yet other controls work (position etc)?

On Fri, Nov 29, 2019 at 10:23 AM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

My Tek 2467B has just started acting up. The Intensity and Readout
Intensity controls suddenly started to be erratic. The voltages to U650
sequencer are delayed by several seconds but can be set to useable
settings, however if changed the trace and/or readouts can suddenly
vanish.
If slowly adjusted to normal intensity and left alone the scope behaves
indefinitely (not a timeout problem).

I have the service manual for the 2465 but have not been able to find one
for the 2467B. Does anyone have one?

The Intensity pot voltages from the 2467B are different from the 2465 and
the 2465 manual.
Intensity ccw 0V to 1.365V cw (2467B)
ccw 0V to 4.55V cw (2465)
Readout Intensity ccw 1.365V to -1.252V cw (2467B) ccw -5V
to
+5V cw (2465)
I searched this forum and apparently the manual and the 2465 that I have
has the intensity pots wired to the U650. My 2467B is wired to the CPU
and
drives U650 from DACs?

The 2467B has a small vertically mounted board near the U650 that I
suspect has something to do with the Intensity and possibly the timed
turn
off that the 2465 does not have.

I suspect either U650 or the NOVRAM battery. I could replace U650 with a
155 0244 00 from a 2465 but the 2467 is 155 0244 01 and I suspect they
may
not be the same because of the timed Bright-eye control. Are they
interchangeable?

I saw in the forum something else to check: “Did you try cleaning the
contacts on the old U950 and re-insert it? My 2467 was all kinds of
glitchy
and twichy, misbehaving in all kinds of ways until I cleaned and
re-seated
the hybrids”.
I am reluctant to disturb this component and cause another problem.

Any suggestions?
PeterB








peter bunge
 

With a slightly bright display the timer shows 6M and counts down to 1M
then 59 secs down to 2 sec but instead of the display turning off the timer
resets to 9M and starts again.
The NOVRAM now seems unlikely to be the problem.
I will take a look at the (from forum):
Did you solve the capacitor leak problem on A5 logic board? Cause all
settings are under dependance of the DAC and when resistor connections are
corroded everything goes wrong, including display points appearing, and
intensity dimming.

On Fri, Nov 29, 2019 at 1:16 PM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

Very confusing. The pot voltages are shown on sheet 5 going to sheet 2 into
the analog mux U2510, then through a discriminator? U2510 to a digital mux
U2220. It is not shown going to an ADC so how does the CPU know what the
values are?
Jumping to the O/P side shown on sheet 2: the O/P of DAC U2101 goes
through analog mux U2530 to amplifiers U2630 then back in through sheet 5
to pins 22 & 23 of the sequencer U650.

Where and what is U950 referred to in the forum to check and clean its
contacts?



On Fri, Nov 29, 2019 at 11:30 AM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

I just found pdf service manuals from Artekmedia and Didier Juges
confirming where the Intensity controls connect.
I would like to buy a printed original manual.
What would delay the voltages to pins 22 & 23 of U650? Can U650 do that
and
yet other controls work (position etc)?

On Fri, Nov 29, 2019 at 10:23 AM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

My Tek 2467B has just started acting up. The Intensity and Readout
Intensity controls suddenly started to be erratic. The voltages to U650
sequencer are delayed by several seconds but can be set to useable
settings, however if changed the trace and/or readouts can suddenly
vanish.
If slowly adjusted to normal intensity and left alone the scope behaves
indefinitely (not a timeout problem).

I have the service manual for the 2465 but have not been able to find
one
for the 2467B. Does anyone have one?

The Intensity pot voltages from the 2467B are different from the 2465
and
the 2465 manual.
Intensity ccw 0V to 1.365V cw (2467B)
ccw 0V to 4.55V cw (2465)
Readout Intensity ccw 1.365V to -1.252V cw (2467B) ccw -5V
to
+5V cw (2465)
I searched this forum and apparently the manual and the 2465 that I
have
has the intensity pots wired to the U650. My 2467B is wired to the CPU
and
drives U650 from DACs?

The 2467B has a small vertically mounted board near the U650 that I
suspect has something to do with the Intensity and possibly the timed
turn
off that the 2465 does not have.

I suspect either U650 or the NOVRAM battery. I could replace U650 with
a
155 0244 00 from a 2465 but the 2467 is 155 0244 01 and I suspect they
may
not be the same because of the timed Bright-eye control. Are they
interchangeable?

I saw in the forum something else to check: “Did you try cleaning the
contacts on the old U950 and re-insert it? My 2467 was all kinds of
glitchy
and twichy, misbehaving in all kinds of ways until I cleaned and
re-seated
the hybrids”.
I am reluctant to disturb this component and cause another problem.

Any suggestions?
PeterB








peter bunge
 

Thanks Chuck, I was following the signal path from the two Intensity pots
on the 2467B schematic, sheets 5 and 2. They do not go to an ADC input but
I'm sure they must. There is something missing on the schematic, and I have
looked at several.
Do you know what capacitors are referred to in this post:
Did you solve the capacitor leak problem on A5 logic board? Cause all
settings are under dependance of the DAC and when resistor connections are
corroded everything goes wrong, including display points appearing, and
intensity dimming.

On Fri, Nov 29, 2019 at 4:57 PM Chuck Harris <cfharris@erols.com> wrote:

Hi Peter,

The 2465 creates an ADC function by using the DAC in concert with
MUX's, Sample-and-hold cells, and the trigger hybrid.

The CPU sets up the Mux to connect the DAC, and a sample and hold
gate to drive the DC trigger threshold input of the trigger hybrid.

The CPU adjusts the trigger threshold until the trigger hybrid just
switches from being less than to being more than the voltage being
measured when the CPU increments the DAC one count.

Tricky, but it was cheap and reliable for the times.

I'm not sure what you mean by a discriminator.

-Chuck Harris

peter bunge wrote:
Very confusing. The pot voltages are shown on sheet 5 going to sheet 2
into
the analog mux U2510, then through a discriminator? U2510 to a digital
mux
U2220. It is not shown going to an ADC so how does the CPU know what the
values are?
Jumping to the O/P side shown on sheet 2: the O/P of DAC U2101 goes
through analog mux U2530 to amplifiers U2630 then back in through sheet 5
to pins 22 & 23 of the sequencer U650.

Where and what is U950 referred to in the forum to check and clean its
contacts?



On Fri, Nov 29, 2019 at 11:30 AM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

I just found pdf service manuals from Artekmedia and Didier Juges
confirming where the Intensity controls connect.
I would like to buy a printed original manual.
What would delay the voltages to pins 22 & 23 of U650? Can U650 do that
and
yet other controls work (position etc)?

On Fri, Nov 29, 2019 at 10:23 AM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

My Tek 2467B has just started acting up. The Intensity and Readout
Intensity controls suddenly started to be erratic. The voltages to U650
sequencer are delayed by several seconds but can be set to useable
settings, however if changed the trace and/or readouts can suddenly
vanish.
If slowly adjusted to normal intensity and left alone the scope behaves
indefinitely (not a timeout problem).

I have the service manual for the 2465 but have not been able to find
one
for the 2467B. Does anyone have one?

The Intensity pot voltages from the 2467B are different from the 2465
and
the 2465 manual.
Intensity ccw 0V to 1.365V cw (2467B)
ccw 0V to 4.55V cw (2465)
Readout Intensity ccw 1.365V to -1.252V cw (2467B) ccw -5V
to
+5V cw (2465)
I searched this forum and apparently the manual and the 2465 that I
have
has the intensity pots wired to the U650. My 2467B is wired to the CPU
and
drives U650 from DACs?

The 2467B has a small vertically mounted board near the U650 that I
suspect has something to do with the Intensity and possibly the timed
turn
off that the 2465 does not have.

I suspect either U650 or the NOVRAM battery. I could replace U650 with
a
155 0244 00 from a 2465 but the 2467 is 155 0244 01 and I suspect they
may
not be the same because of the timed Bright-eye control. Are they
interchangeable?

I saw in the forum something else to check: “Did you try cleaning the
contacts on the old U950 and re-insert it? My 2467 was all kinds of
glitchy
and twichy, misbehaving in all kinds of ways until I cleaned and
re-seated
the hybrids”.
I am reluctant to disturb this component and cause another problem.

Any suggestions?
PeterB










Chuck Harris <cfharris@...>
 

There is no ADC part in the 2465 family scopes.

There is a DAC that is used as a part of an ADC
that is made from the DAC, CPU, MUX's, Sample and
Hold cells, and the trigger hybrid. The trigger
hybrid is used as the comparator that compares the
DAC output to the pot's wiper voltage.

The voltages get to the trigger hybrid by way of
a pair of muxes.

The capacitors referred to in the post are on the
A5 controller card on scopes with serial numbers
greater than B049999.

They are ordinary power supply bypass capacitors,
that because of the abuse of their being soldered
to the board by an oven, leak electrolyte all over
themselves, and the circuit board. The electrolyte
is highly corrosive to copper, and highly conductive
to electricity. It eats the copper traces, and
shorts out other components and traces.

They are the only surface mount electrolytic capacitors
on the board. Three are near the DAC, and the other is
on a distant corner.

If your A5 controller board has these capacitors, you
must replace them before anything else the scope does
will make much sense... Assuming that they haven't been
replaced already.

-Chuck Harris



peter bunge wrote:

Thanks Chuck, I was following the signal path from the two Intensity pots
on the 2467B schematic, sheets 5 and 2. They do not go to an ADC input but
I'm sure they must. There is something missing on the schematic, and I have
looked at several.
Do you know what capacitors are referred to in this post:
Did you solve the capacitor leak problem on A5 logic board? Cause all
settings are under dependance of the DAC and when resistor connections are
corroded everything goes wrong, including display points appearing, and
intensity dimming.


Siggi
 

The comparator U2510, an LM311, is used to compare the DAC output to pot
readings, and the MPU uses this with successive approximation to make a
software ADC. This is described in the “Theory of Operation” section.

The trigger hybrid is not involved in pot scanning, though otherwise it
works the way Chuck describes it.

On Sat, Nov 30, 2019 at 04:49 Chuck Harris <cfharris@erols.com> wrote:

There is no ADC part in the 2465 family scopes.

There is a DAC that is used as a part of an ADC
that is made from the DAC, CPU, MUX's, Sample and
Hold cells, and the trigger hybrid. The trigger
hybrid is used as the comparator that compares the
DAC output to the pot's wiper voltage.

The voltages get to the trigger hybrid by way of
a pair of muxes.

The capacitors referred to in the post are on the
A5 controller card on scopes with serial numbers
greater than B049999.

They are ordinary power supply bypass capacitors,
that because of the abuse of their being soldered
to the board by an oven, leak electrolyte all over
themselves, and the circuit board. The electrolyte
is highly corrosive to copper, and highly conductive
to electricity. It eats the copper traces, and
shorts out other components and traces.

They are the only surface mount electrolytic capacitors
on the board. Three are near the DAC, and the other is
on a distant corner.

If your A5 controller board has these capacitors, you
must replace them before anything else the scope does
will make much sense... Assuming that they haven't been
replaced already.

-Chuck Harris



peter bunge wrote:
Thanks Chuck, I was following the signal path from the two Intensity pots
on the 2467B schematic, sheets 5 and 2. They do not go to an ADC input
but
I'm sure they must. There is something missing on the schematic, and I
have
looked at several.
Do you know what capacitors are referred to in this post:
Did you solve the capacitor leak problem on A5 logic board? Cause all
settings are under dependance of the DAC and when resistor connections
are
corroded everything goes wrong, including display points appearing, and
intensity dimming.




Chuck Harris <cfharris@...>
 

Hi Siggi,

Yes, I keep forgetting they did that. Putting a
cheap little LM311 on the A5 board simplifies the
circuit board routing greatly, and keeps the noise down.

The trigger hybrid is used as the comparator for
anything related to parametric measurements... and,
well the trigger.

I don't think I have ever seen that LM311 go bad...

Thanks for keeping me honest.

-Chuck Harris

Siggi wrote:

The comparator U2510, an LM311, is used to compare the DAC output to pot
readings, and the MPU uses this with successive approximation to make a
software ADC. This is described in the “Theory of Operation” section.

The trigger hybrid is not involved in pot scanning, though otherwise it
works the way Chuck describes it.

On Sat, Nov 30, 2019 at 04:49 Chuck Harris <cfharris@erols.com> wrote:

There is no ADC part in the 2465 family scopes.

There is a DAC that is used as a part of an ADC
that is made from the DAC, CPU, MUX's, Sample and
Hold cells, and the trigger hybrid. The trigger
hybrid is used as the comparator that compares the
DAC output to the pot's wiper voltage.

The voltages get to the trigger hybrid by way of
a pair of muxes.


peter bunge
 

Thanks Siggi and Chuck, I have been printing the 2467B manual I bought from
Artekmedia. I hate working from a computer screen and like to have paper to
highlight or write notes on. I will check the A5 capacitors and am reading
the manual.
I bought a spare horizontal chip and sequencer chip on Ebay and, because
the guy seemed to know about these problems asked about my issues. Here,
with his permission, are his replies through Ebay's limited messages. I
have not edited his English which I'm sure is much better than my rendition
of his language. I am very fortunate to have stumbled on this source of
knowledge. (I bought the chips for a dead 2465, not my 2467B)

Hi Peter!

Many thanks for your purchases and for repeated customer.

To answer on your questions, I might not have more knowledge than yours, I
developed some experience about these magnificent scopes when I did some
work on them long time time ago, I learned some but I don’t know the most
of it, I sold all of them and kept one 2465B and some spare parts that I
put them for sale here, any regarding the problem you have I don’t think
the U650 is the one because I had the same problem before...

...and I found the problem coming from some leaking SMD electrolytic caps
on the controller board, they are 4 of them there need to be replaced, I
did it then the screen came back to work correctly, other thing, they are
more of electrolytic caps on the main board need to be checked, they are
all aged more 20 years, but the one in the mentioned they go bad often,
other thing make sure if any cold solder somewhere in any part by using a
pencil and touch parts feet here and there........

You never know you can find one cold solder somewhere, other important
thing, you need to check all electrolytic caps in the main power supply,
some go bad often too, check if any acid leaks or swollen cap, these are
the first thing you need to do, other easy way I use to do, I use to have
multiple scopes 2465s so I keep swap the hybrid ICs until I find one is
bad, especially the vertical IC and Zaxis go bad faster than others the
2465 and 2467 have the same hybrid modules, you can do it....

As you mentioned the memory battery 🔋, it doesn’t have anything to do with
your problem because when the battery goes bad or low in power the stored
calibration data will vanished then you will have a serious problem, you
will start to see on the screen in the place of readout lines like this
???????????????, so you need to replace the battery by new one and you need
to recalibrate your scope again, these scopes have more than 20 years in
their lives........

So it is time to replace the battery before you loose the stored
calibration data, if you know how to do it then do now to avoid any future
calibration problem.

Regarding the question about 0244-00 or 0244-01 if any difference, I think
they are the same with a little bit of changes from the manufacturer, 00 is
the earlier 01 is the later but they have the same pin out and work the
same too.

Once I had a talk with the engineer who developed the 2465, it was a quiet
honor to talk to him.....

I did ask him about about a problem o had, the screen was acting
erratically and sometimes go away, I swapped all the modules, checked every
part, but I couldn’t find it, he right a way told me check a coil with 4
feet near by the Zaxis vertical maybe, he said one of the foot has cold
solder, I was shocked he was right !! I resolder it and worked fine, and I
did ask hi about the U800 problems too, it is a customs complex IC they go
bad over time because of excessive heat, he said when......

He said when we created this IC they didn’t know it will get hot 🥵 and
they didn’t design it with a socket to be easy to replace it without
damaging the PCB, he said by the time the IC started to fail over time it
was to late to redesign it with socket because the production line of this
scope cane to end, he advices me to add a socket to it if I want to and to
add a heat sink on top to reduce the heat and the IC will last longer, but
make sure the heat sink don’t connect the 2 screws together…

Because the 2 screws that hold the U800 one of them has positive voltage,
so avoid to screw a heat sink on both screws, just one side and other screw
left alone to avoid to short it, there is an article online showing how to
add a heat sink to U800 safely.

I hope I gave you some hints that can help you, if you have more questions
just ask and thanks for your purchases….

Oh I forgot to answer your question regarding how to remove the U800, well,
back then I used a pump with heated tip in one piece, i desoldered one foot
after another and make sure the foot is clear, and then after I finish all
I put a flat screw driver underneath of the IC and try to push up slowly, I
don’t force it, if it doesn’t move up I will go back and see if any foot
still not cleared, it is a difficult task and slow but it is better to be
in safe mode than damage the IC or PCB….

Now I have a much better electric pump desolder gun with controlled
temperature, it does a very good job and faster with safe temperature.

Good luck

On Sat, Nov 30, 2019 at 4:20 AM Siggi <siggi@undo.com> wrote:

The comparator U2510, an LM311, is used to compare the DAC output to pot
readings, and the MPU uses this with successive approximation to make a
software ADC. This is described in the “Theory of Operation” section.

The trigger hybrid is not involved in pot scanning, though otherwise it
works the way Chuck describes it.

On Sat, Nov 30, 2019 at 04:49 Chuck Harris <cfharris@erols.com> wrote:

There is no ADC part in the 2465 family scopes.

There is a DAC that is used as a part of an ADC
that is made from the DAC, CPU, MUX's, Sample and
Hold cells, and the trigger hybrid. The trigger
hybrid is used as the comparator that compares the
DAC output to the pot's wiper voltage.

The voltages get to the trigger hybrid by way of
a pair of muxes.

The capacitors referred to in the post are on the
A5 controller card on scopes with serial numbers
greater than B049999.

They are ordinary power supply bypass capacitors,
that because of the abuse of their being soldered
to the board by an oven, leak electrolyte all over
themselves, and the circuit board. The electrolyte
is highly corrosive to copper, and highly conductive
to electricity. It eats the copper traces, and
shorts out other components and traces.

They are the only surface mount electrolytic capacitors
on the board. Three are near the DAC, and the other is
on a distant corner.

If your A5 controller board has these capacitors, you
must replace them before anything else the scope does
will make much sense... Assuming that they haven't been
replaced already.

-Chuck Harris



peter bunge wrote:
Thanks Chuck, I was following the signal path from the two Intensity
pots
on the 2467B schematic, sheets 5 and 2. They do not go to an ADC input
but
I'm sure they must. There is something missing on the schematic, and I
have
looked at several.
Do you know what capacitors are referred to in this post:
Did you solve the capacitor leak problem on A5 logic board? Cause all
settings are under dependance of the DAC and when resistor connections
are
corroded everything goes wrong, including display points appearing, and
intensity dimming.






Chuck Harris <cfharris@...>
 

Hi Peter,

A whole lot of what you read on the internet about repairs
is very specific to a single one time failure/repair, that someone,
thought to document. That repair is then amplified, by the
megaphone that is the internet, to the stature of a legend, lore,
or meme.

It becomes fact by the acclamation of folks that couldn't find and
fix a complicated original failure if it bit them in the butt.

Folks read (or watch) these highly public repairs and think:
Jim-Bob Boy says gizfloobles fail in this way, so my non working
gizflooble surely has failed this way too... Or, Yee gads! OMG!
Maybe my currently working gizflooble Will fail this way soon!

The legends of the U800 failures are largely in this category.
I firmly believe hundreds, if not thousands have been destroyed by
well meaning, but ignorant, messings around with this part.

What do I mean destroyed? Just that. A probe slips while you are
trying to fit the failure of your scope into the frame of U800 being
the root of all 2465 failures, and another U800 is destroyed...

By the rules governing internet memes, your accidentally destroyed
U800 is another win for the U800's are unreliable legend. Don't
forget to tell your friends...

Another way U800's get destroyed is at root 100% tektronix's fault:

Early in the design, Tek thought U800 would need a heat sink, and
(contrary to the text you quoted below), after production, they
found it didn't. Rather than change U800's package, to a much cheaper
DIP, and do a re-spin of the PCB design, they cobbled together a fix
in production ... a fix involving several lock washers used in an
inappropriate manner, as spacers.

The IC package they used had just enough pins to handle U800's needs,
*if* they used the heatsink tab (and heatsink) to connect the -5V bias
to U800. This was a natural thing to do because the -5V bias, biases
the substrate (silicon wafer) of the IC, and the substrate was already
soldered to the copper frame that includes the heatsink tab...

Under U800 the PCB has a copper fill to which both of U800's heatsink
mounting studs are attached. This copper fill is routed to the -5V
bias supply, so both studs are at -5V (contrary to what you quoted
below).

[Note: All DIP packages are designed to set up off of the board a
little bit, allowing air to flow under the package. This is part
of the normal cooling function of the DIP package, and U800's DIP
package contains this spacing, just like all DIP packages do.]

Without a heat sink to fill the space under U800, U800's leads are
just a little bit too long to allow the heatsink tab (and bottom of
U800) to be clamped down tight to the PCB, by the studs.

If you were to try to tighten U800 down flat, its leads extra length
would break out the top of U800's package. So, prevent this, and to
fill the extra space under the tab, tektronix could have made a little
copper spacer out of a strip of copper flashing, with a couple of holes
punched in it to fit over the mounting studs... Or, they could simply
do what they did, which was: drop a couple of star lock washers over
the studs, filling the space, patting themselves on the back for saving
$0.05, and walking away.

If you are a nervous Nellie sort, when you see a nut, you habitually
give it a little twist to make sure it is tight enough. Experience has
taught you that such connections sometimes corrode, making bad grounds,
and giving a little extra twist breaks the corrosion, often restoring
reliable operation...

If you do this to U800, you will drive the star washer/spacer into the
relatively soft fiberglass PCB, eliminating the dubious spacer function
of the star lockwashers, and often breaking out the top of U800's package.

When the package breaks moisture gets into the package. Which has been
proven to make U800 behave erratically.

If you install a heatsink to the stud with the tab, and crank down on
the nut, you may also drive the star washer into the PCB, and break
out the top of U800's package.

If you glue a heatsink to the top of U800, the adhesive will often
release, and leave a heatsink rattling about in your scope, shorting
what it may...( I can't tell you how many such heatsinks I have found
rattling about in customer scopes...)

Please leave your U800 alone! It doesn't want to be the next example
of how unreliable U800 is.

Also, and this is very important:

The 2465 is designed to operate at the searingly high temperature
of 55C! That is not the temperature inside of the case, but rather
the temperature *in the room*!

If you aren't a Centigrade buff, 55C is 131F!

That is medium rare if you are cooking a steak.

I don't know about you, but humans are not rated to operate at 131F.

How is a chip that is designed to run at a room temperature that is
as hot as the steak on your grill -- all day long --, going to need
extra cooling to run at normal room temperature?

[I mean, even if tek messed up a little bit in their heat calculations,
it isn't going to ever get that hot while *you* are using your scope.]

Food for thought.

-Chuck Harris

peter bunge wrote:

Thanks Siggi and Chuck, I have been printing the 2467B manual I bought from
Artekmedia. I hate working from a computer screen and like to have paper to
highlight or write notes on. I will check the A5 capacitors and am reading
the manual.
I bought a spare horizontal chip and sequencer chip on Ebay and, because
the guy seemed to know about these problems asked about my issues. Here,
with his permission, are his replies through Ebay's limited messages. I
have not edited his English which I'm sure is much better than my rendition
of his language. I am very fortunate to have stumbled on this source of
knowledge. (I bought the chips for a dead 2465, not my 2467B)

Hi Peter!

Many thanks for your purchases and for repeated customer.

To answer on your questions, I might not have more knowledge than yours, I
developed some experience about these magnificent scopes when I did some
work on them long time time ago, I learned some but I don’t know the most
of it, I sold all of them and kept one 2465B and some spare parts that I
put them for sale here, any regarding the problem you have I don’t think
the U650 is the one because I had the same problem before...

...and I found the problem coming from some leaking SMD electrolytic caps
on the controller board, they are 4 of them there need to be replaced, I
did it then the screen came back to work correctly, other thing, they are
more of electrolytic caps on the main board need to be checked, they are
all aged more 20 years, but the one in the mentioned they go bad often,
other thing make sure if any cold solder somewhere in any part by using a
pencil and touch parts feet here and there........

You never know you can find one cold solder somewhere, other important
thing, you need to check all electrolytic caps in the main power supply,
some go bad often too, check if any acid leaks or swollen cap, these are
the first thing you need to do, other easy way I use to do, I use to have
multiple scopes 2465s so I keep swap the hybrid ICs until I find one is
bad, especially the vertical IC and Zaxis go bad faster than others the
2465 and 2467 have the same hybrid modules, you can do it....

As you mentioned the memory battery 🔋, it doesn’t have anything to do with
your problem because when the battery goes bad or low in power the stored
calibration data will vanished then you will have a serious problem, you
will start to see on the screen in the place of readout lines like this
???????????????, so you need to replace the battery by new one and you need
to recalibrate your scope again, these scopes have more than 20 years in
their lives........

So it is time to replace the battery before you loose the stored
calibration data, if you know how to do it then do now to avoid any future
calibration problem.

Regarding the question about 0244-00 or 0244-01 if any difference, I think
they are the same with a little bit of changes from the manufacturer, 00 is
the earlier 01 is the later but they have the same pin out and work the
same too.

Once I had a talk with the engineer who developed the 2465, it was a quiet
honor to talk to him.....

I did ask him about about a problem o had, the screen was acting
erratically and sometimes go away, I swapped all the modules, checked every
part, but I couldn’t find it, he right a way told me check a coil with 4
feet near by the Zaxis vertical maybe, he said one of the foot has cold
solder, I was shocked he was right !! I resolder it and worked fine, and I
did ask hi about the U800 problems too, it is a customs complex IC they go
bad over time because of excessive heat, he said when......

He said when we created this IC they didn’t know it will get hot 🥵 and
they didn’t design it with a socket to be easy to replace it without
damaging the PCB, he said by the time the IC started to fail over time it
was to late to redesign it with socket because the production line of this
scope cane to end, he advices me to add a socket to it if I want to and to
add a heat sink on top to reduce the heat and the IC will last longer, but
make sure the heat sink don’t connect the 2 screws together…

Because the 2 screws that hold the U800 one of them has positive voltage,
so avoid to screw a heat sink on both screws, just one side and other screw
left alone to avoid to short it, there is an article online showing how to
add a heat sink to U800 safely.

I hope I gave you some hints that can help you, if you have more questions
just ask and thanks for your purchases….

Oh I forgot to answer your question regarding how to remove the U800, well,
back then I used a pump with heated tip in one piece, i desoldered one foot
after another and make sure the foot is clear, and then after I finish all
I put a flat screw driver underneath of the IC and try to push up slowly, I
don’t force it, if it doesn’t move up I will go back and see if any foot
still not cleared, it is a difficult task and slow but it is better to be
in safe mode than damage the IC or PCB….

Now I have a much better electric pump desolder gun with controlled
temperature, it does a very good job and faster with safe temperature.

Good luck


On Sat, Nov 30, 2019 at 4:20 AM Siggi <siggi@undo.com> wrote:

The comparator U2510, an LM311, is used to compare the DAC output to pot
readings, and the MPU uses this with successive approximation to make a
software ADC. This is described in the “Theory of Operation” section.

The trigger hybrid is not involved in pot scanning, though otherwise it
works the way Chuck describes it.

On Sat, Nov 30, 2019 at 04:49 Chuck Harris <cfharris@erols.com> wrote:

There is no ADC part in the 2465 family scopes.

There is a DAC that is used as a part of an ADC
that is made from the DAC, CPU, MUX's, Sample and
Hold cells, and the trigger hybrid. The trigger
hybrid is used as the comparator that compares the
DAC output to the pot's wiper voltage.

The voltages get to the trigger hybrid by way of
a pair of muxes.

The capacitors referred to in the post are on the
A5 controller card on scopes with serial numbers
greater than B049999.

They are ordinary power supply bypass capacitors,
that because of the abuse of their being soldered
to the board by an oven, leak electrolyte all over
themselves, and the circuit board. The electrolyte
is highly corrosive to copper, and highly conductive
to electricity. It eats the copper traces, and
shorts out other components and traces.

They are the only surface mount electrolytic capacitors
on the board. Three are near the DAC, and the other is
on a distant corner.

If your A5 controller board has these capacitors, you
must replace them before anything else the scope does
will make much sense... Assuming that they haven't been
replaced already.

-Chuck Harris



peter bunge wrote:
Thanks Chuck, I was following the signal path from the two Intensity
pots
on the 2467B schematic, sheets 5 and 2. They do not go to an ADC input
but
I'm sure they must. There is something missing on the schematic, and I
have
looked at several.
Do you know what capacitors are referred to in this post:
Did you solve the capacitor leak problem on A5 logic board? Cause all
settings are under dependance of the DAC and when resistor connections
are
corroded everything goes wrong, including display points appearing, and
intensity dimming.








GerryR <totalautomation1@...>
 

When I had my 2465A apart to replace the battery and for calibration, I used an infrared temp probe to monitor the U800. The max temperature it reached after a couple hours on-time was 135 deg F. Once in the case and having forced cooling from the fan, I assume it is much lower. I had read of the "heatsink mod" but couldn't see where it was needed after monitoring the temperature. I did read somewhere, that Tektronix later had some other vendor making that IC, and they had problems due to failure of the internal chip-to-heatsink bond, which caused the U800 to overheat. I assume that was a production process problem and was corrected. This may be what started the "reputation" of the U800.

Gerry
KK4GER

----- Original Message -----
From: "Chuck Harris" <cfharris@erols.com>
To: <TekScopes@groups.io>
Sent: Sunday, December 01, 2019 12:41 PM
Subject: Re: [TekScopes] Tek 2467B Erratic Intensity controls


Hi Peter,

A whole lot of what you read on the internet about repairs
is very specific to a single one time failure/repair, that someone,
thought to document. That repair is then amplified, by the
megaphone that is the internet, to the stature of a legend, lore,
or meme.

It becomes fact by the acclamation of folks that couldn't find and
fix a complicated original failure if it bit them in the butt.

Folks read (or watch) these highly public repairs and think:
Jim-Bob Boy says gizfloobles fail in this way, so my non working
gizflooble surely has failed this way too... Or, Yee gads! OMG!
Maybe my currently working gizflooble Will fail this way soon!

The legends of the U800 failures are largely in this category.
I firmly believe hundreds, if not thousands have been destroyed by
well meaning, but ignorant, messings around with this part.

What do I mean destroyed? Just that. A probe slips while you are
trying to fit the failure of your scope into the frame of U800 being
the root of all 2465 failures, and another U800 is destroyed...

By the rules governing internet memes, your accidentally destroyed
U800 is another win for the U800's are unreliable legend. Don't
forget to tell your friends...

Another way U800's get destroyed is at root 100% tektronix's fault:

Early in the design, Tek thought U800 would need a heat sink, and
(contrary to the text you quoted below), after production, they
found it didn't. Rather than change U800's package, to a much cheaper
DIP, and do a re-spin of the PCB design, they cobbled together a fix
in production ... a fix involving several lock washers used in an
inappropriate manner, as spacers.

The IC package they used had just enough pins to handle U800's needs,
*if* they used the heatsink tab (and heatsink) to connect the -5V bias
to U800. This was a natural thing to do because the -5V bias, biases
the substrate (silicon wafer) of the IC, and the substrate was already
soldered to the copper frame that includes the heatsink tab...

Under U800 the PCB has a copper fill to which both of U800's heatsink
mounting studs are attached. This copper fill is routed to the -5V
bias supply, so both studs are at -5V (contrary to what you quoted
below).

[Note: All DIP packages are designed to set up off of the board a
little bit, allowing air to flow under the package. This is part
of the normal cooling function of the DIP package, and U800's DIP
package contains this spacing, just like all DIP packages do.]

Without a heat sink to fill the space under U800, U800's leads are
just a little bit too long to allow the heatsink tab (and bottom of
U800) to be clamped down tight to the PCB, by the studs.

If you were to try to tighten U800 down flat, its leads extra length
would break out the top of U800's package. So, prevent this, and to
fill the extra space under the tab, tektronix could have made a little
copper spacer out of a strip of copper flashing, with a couple of holes
punched in it to fit over the mounting studs... Or, they could simply
do what they did, which was: drop a couple of star lock washers over
the studs, filling the space, patting themselves on the back for saving
$0.05, and walking away.

If you are a nervous Nellie sort, when you see a nut, you habitually
give it a little twist to make sure it is tight enough. Experience has
taught you that such connections sometimes corrode, making bad grounds,
and giving a little extra twist breaks the corrosion, often restoring
reliable operation...

If you do this to U800, you will drive the star washer/spacer into the
relatively soft fiberglass PCB, eliminating the dubious spacer function
of the star lockwashers, and often breaking out the top of U800's package.

When the package breaks moisture gets into the package. Which has been
proven to make U800 behave erratically.

If you install a heatsink to the stud with the tab, and crank down on
the nut, you may also drive the star washer into the PCB, and break
out the top of U800's package.

If you glue a heatsink to the top of U800, the adhesive will often
release, and leave a heatsink rattling about in your scope, shorting
what it may...( I can't tell you how many such heatsinks I have found
rattling about in customer scopes...)

Please leave your U800 alone! It doesn't want to be the next example
of how unreliable U800 is.

Also, and this is very important:

The 2465 is designed to operate at the searingly high temperature
of 55C! That is not the temperature inside of the case, but rather
the temperature *in the room*!

If you aren't a Centigrade buff, 55C is 131F!

That is medium rare if you are cooking a steak.

I don't know about you, but humans are not rated to operate at 131F.

How is a chip that is designed to run at a room temperature that is
as hot as the steak on your grill -- all day long --, going to need
extra cooling to run at normal room temperature?

[I mean, even if tek messed up a little bit in their heat calculations,
it isn't going to ever get that hot while *you* are using your scope.]

Food for thought.

-Chuck Harris

peter bunge wrote:
Thanks Siggi and Chuck, I have been printing the 2467B manual I bought from
Artekmedia. I hate working from a computer screen and like to have paper to
highlight or write notes on. I will check the A5 capacitors and am reading
the manual.
I bought a spare horizontal chip and sequencer chip on Ebay and, because
the guy seemed to know about these problems asked about my issues. Here,
with his permission, are his replies through Ebay's limited messages. I
have not edited his English which I'm sure is much better than my rendition
of his language. I am very fortunate to have stumbled on this source of
knowledge. (I bought the chips for a dead 2465, not my 2467B)

Hi Peter!

Many thanks for your purchases and for repeated customer.

To answer on your questions, I might not have more knowledge than yours, I
developed some experience about these magnificent scopes when I did some
work on them long time time ago, I learned some but I don’t know the most
of it, I sold all of them and kept one 2465B and some spare parts that I
put them for sale here, any regarding the problem you have I don’t think
the U650 is the one because I had the same problem before...

...and I found the problem coming from some leaking SMD electrolytic caps
on the controller board, they are 4 of them there need to be replaced, I
did it then the screen came back to work correctly, other thing, they are
more of electrolytic caps on the main board need to be checked, they are
all aged more 20 years, but the one in the mentioned they go bad often,
other thing make sure if any cold solder somewhere in any part by using a
pencil and touch parts feet here and there........

You never know you can find one cold solder somewhere, other important
thing, you need to check all electrolytic caps in the main power supply,
some go bad often too, check if any acid leaks or swollen cap, these are
the first thing you need to do, other easy way I use to do, I use to have
multiple scopes 2465s so I keep swap the hybrid ICs until I find one is
bad, especially the vertical IC and Zaxis go bad faster than others the
2465 and 2467 have the same hybrid modules, you can do it....

As you mentioned the memory battery 🔋, it doesn’t have anything to do with
your problem because when the battery goes bad or low in power the stored
calibration data will vanished then you will have a serious problem, you
will start to see on the screen in the place of readout lines like this
???????????????, so you need to replace the battery by new one and you need
to recalibrate your scope again, these scopes have more than 20 years in
their lives........

So it is time to replace the battery before you loose the stored
calibration data, if you know how to do it then do now to avoid any future
calibration problem.

Regarding the question about 0244-00 or 0244-01 if any difference, I think
they are the same with a little bit of changes from the manufacturer, 00 is
the earlier 01 is the later but they have the same pin out and work the
same too.

Once I had a talk with the engineer who developed the 2465, it was a quiet
honor to talk to him.....

I did ask him about about a problem o had, the screen was acting
erratically and sometimes go away, I swapped all the modules, checked every
part, but I couldn’t find it, he right a way told me check a coil with 4
feet near by the Zaxis vertical maybe, he said one of the foot has cold
solder, I was shocked he was right !! I resolder it and worked fine, and I
did ask hi about the U800 problems too, it is a customs complex IC they go
bad over time because of excessive heat, he said when......

He said when we created this IC they didn’t know it will get hot 🥵 and
they didn’t design it with a socket to be easy to replace it without
damaging the PCB, he said by the time the IC started to fail over time it
was to late to redesign it with socket because the production line of this
scope cane to end, he advices me to add a socket to it if I want to and to
add a heat sink on top to reduce the heat and the IC will last longer, but
make sure the heat sink don’t connect the 2 screws together…

Because the 2 screws that hold the U800 one of them has positive voltage,
so avoid to screw a heat sink on both screws, just one side and other screw
left alone to avoid to short it, there is an article online showing how to
add a heat sink to U800 safely.

I hope I gave you some hints that can help you, if you have more questions
just ask and thanks for your purchases….

Oh I forgot to answer your question regarding how to remove the U800, well,
back then I used a pump with heated tip in one piece, i desoldered one foot
after another and make sure the foot is clear, and then after I finish all
I put a flat screw driver underneath of the IC and try to push up slowly, I
don’t force it, if it doesn’t move up I will go back and see if any foot
still not cleared, it is a difficult task and slow but it is better to be
in safe mode than damage the IC or PCB….

Now I have a much better electric pump desolder gun with controlled
temperature, it does a very good job and faster with safe temperature.

Good luck


On Sat, Nov 30, 2019 at 4:20 AM Siggi <siggi@undo.com> wrote:

The comparator U2510, an LM311, is used to compare the DAC output to pot
readings, and the MPU uses this with successive approximation to make a
software ADC. This is described in the “Theory of Operation” section.

The trigger hybrid is not involved in pot scanning, though otherwise it
works the way Chuck describes it.

On Sat, Nov 30, 2019 at 04:49 Chuck Harris <cfharris@erols.com> wrote:

There is no ADC part in the 2465 family scopes.

There is a DAC that is used as a part of an ADC
that is made from the DAC, CPU, MUX's, Sample and
Hold cells, and the trigger hybrid. The trigger
hybrid is used as the comparator that compares the
DAC output to the pot's wiper voltage.

The voltages get to the trigger hybrid by way of
a pair of muxes.

The capacitors referred to in the post are on the
A5 controller card on scopes with serial numbers
greater than B049999.

They are ordinary power supply bypass capacitors,
that because of the abuse of their being soldered
to the board by an oven, leak electrolyte all over
themselves, and the circuit board. The electrolyte
is highly corrosive to copper, and highly conductive
to electricity. It eats the copper traces, and
shorts out other components and traces.

They are the only surface mount electrolytic capacitors
on the board. Three are near the DAC, and the other is
on a distant corner.

If your A5 controller board has these capacitors, you
must replace them before anything else the scope does
will make much sense... Assuming that they haven't been
replaced already.

-Chuck Harris



peter bunge wrote:
Thanks Chuck, I was following the signal path from the two Intensity
pots
on the 2467B schematic, sheets 5 and 2. They do not go to an ADC input
but
I'm sure they must. There is something missing on the schematic, and I
have
looked at several.
Do you know what capacitors are referred to in this post:
Did you solve the capacitor leak problem on A5 logic board? Cause all
settings are under dependance of the DAC and when resistor connections
are
corroded everything goes wrong, including display points appearing, and
intensity dimming.








peter bunge
 

Thanks Chuck;
however I bought the U800 to repair a friend's 2465 scope that was sitting
on a shelf with the feet overhanging so the cooling holes in the bottom of
the 'scope were blocked. This may not have been the cause but the 'scope
failed suddenly.
My present problem with a 2467B S/N B051193 has nothing to do with U800 but
may be associated with U650. I mentioned the problems as general interest.
The symptoms are that changes in either of the intensity pots takes
several, and up to many (30 or more), seconds to respond either in
intensity on the screen, or voltages at the sequencer pins. Without
touching anything on the 'scope the 'trace turn off' counts down from
minutes, to 59 seconds, down to 2 seconds, then starts again at (8) minutes
without shutting off the display. So that feature is not working. At very
bright it did drop the intensity after 30 seconds but did not turn it off
so it may be partly working. I remember it turned the displays off until a
knob was moved.
Delta v and delta t are erratic placing the dotted lines on the screen, and
dt sometime shows dv lines or nothing. And they have the same sluggish
delay to doing anything.
The 5 capacitors have been professionally replaced before I got the 'scope
and they look good. There could still be corrosion somewhere but I don't
intend to replace them haphazardly without some evidence. I washed around
them by brushing Isopropyl Alcohol and letting it run down onto paper
towel. There is no evidence of a change. I don't think they are the problem.
I re-soldered the legs of the coil and saw no change, not that I expected
to.
I was following the troubleshooting (page 458 in several pdfs) that asks if
the LEDs respond to "A/B Trig" being pressed. This is confusing since they
don't define 'respond'. Fortunately I have a 2465 with Tek manual which
asks the same thing. On the 2465 the displays are switched each
press/release but on my 2467B they change back when released. Is this
normal? Another problem is that if I go to 4 as directed it asks about
"signals conforming to guidelines at the left" and that page is missing or
out of order in the pdf. My 2465 Tek manual shows the page I should see.
However with my new interpretation of 'respond' I was being led astray so
the answer should have been 'no' and I should not have gone to 4. The next
step is "do scale factors appear with readout intensity full cw?" Yes takes
me to "repair LED or front panel interconnect", unlikely, so this takes me
nowhere.
I swapped sequencer U650 155-0244-01 with 155-0244-00 from the 2465 but
there was no change.
Still struggling but getting a better understanding. Time to 'scope around
the circuits.
Peter

On Sun, Dec 1, 2019 at 12:42 PM Chuck Harris <cfharris@erols.com> wrote:

Hi Peter,

A whole lot of what you read on the internet about repairs
is very specific to a single one time failure/repair, that someone,
thought to document. That repair is then amplified, by the
megaphone that is the internet, to the stature of a legend, lore,
or meme.

It becomes fact by the acclamation of folks that couldn't find and
fix a complicated original failure if it bit them in the butt.

Folks read (or watch) these highly public repairs and think:
Jim-Bob Boy says gizfloobles fail in this way, so my non working
gizflooble surely has failed this way too... Or, Yee gads! OMG!
Maybe my currently working gizflooble Will fail this way soon!

The legends of the U800 failures are largely in this category.
I firmly believe hundreds, if not thousands have been destroyed by
well meaning, but ignorant, messings around with this part.

What do I mean destroyed? Just that. A probe slips while you are
trying to fit the failure of your scope into the frame of U800 being
the root of all 2465 failures, and another U800 is destroyed...

By the rules governing internet memes, your accidentally destroyed
U800 is another win for the U800's are unreliable legend. Don't
forget to tell your friends...

Another way U800's get destroyed is at root 100% tektronix's fault:

Early in the design, Tek thought U800 would need a heat sink, and
(contrary to the text you quoted below), after production, they
found it didn't. Rather than change U800's package, to a much cheaper
DIP, and do a re-spin of the PCB design, they cobbled together a fix
in production ... a fix involving several lock washers used in an
inappropriate manner, as spacers.

The IC package they used had just enough pins to handle U800's needs,
*if* they used the heatsink tab (and heatsink) to connect the -5V bias
to U800. This was a natural thing to do because the -5V bias, biases
the substrate (silicon wafer) of the IC, and the substrate was already
soldered to the copper frame that includes the heatsink tab...

Under U800 the PCB has a copper fill to which both of U800's heatsink
mounting studs are attached. This copper fill is routed to the -5V
bias supply, so both studs are at -5V (contrary to what you quoted
below).

[Note: All DIP packages are designed to set up off of the board a
little bit, allowing air to flow under the package. This is part
of the normal cooling function of the DIP package, and U800's DIP
package contains this spacing, just like all DIP packages do.]

Without a heat sink to fill the space under U800, U800's leads are
just a little bit too long to allow the heatsink tab (and bottom of
U800) to be clamped down tight to the PCB, by the studs.

If you were to try to tighten U800 down flat, its leads extra length
would break out the top of U800's package. So, prevent this, and to
fill the extra space under the tab, tektronix could have made a little
copper spacer out of a strip of copper flashing, with a couple of holes
punched in it to fit over the mounting studs... Or, they could simply
do what they did, which was: drop a couple of star lock washers over
the studs, filling the space, patting themselves on the back for saving
$0.05, and walking away.

If you are a nervous Nellie sort, when you see a nut, you habitually
give it a little twist to make sure it is tight enough. Experience has
taught you that such connections sometimes corrode, making bad grounds,
and giving a little extra twist breaks the corrosion, often restoring
reliable operation...

If you do this to U800, you will drive the star washer/spacer into the
relatively soft fiberglass PCB, eliminating the dubious spacer function
of the star lockwashers, and often breaking out the top of U800's package.

When the package breaks moisture gets into the package. Which has been
proven to make U800 behave erratically.

If you install a heatsink to the stud with the tab, and crank down on
the nut, you may also drive the star washer into the PCB, and break
out the top of U800's package.

If you glue a heatsink to the top of U800, the adhesive will often
release, and leave a heatsink rattling about in your scope, shorting
what it may...( I can't tell you how many such heatsinks I have found
rattling about in customer scopes...)

Please leave your U800 alone! It doesn't want to be the next example
of how unreliable U800 is.

Also, and this is very important:

The 2465 is designed to operate at the searingly high temperature
of 55C! That is not the temperature inside of the case, but rather
the temperature *in the room*!

If you aren't a Centigrade buff, 55C is 131F!

That is medium rare if you are cooking a steak.

I don't know about you, but humans are not rated to operate at 131F.

How is a chip that is designed to run at a room temperature that is
as hot as the steak on your grill -- all day long --, going to need
extra cooling to run at normal room temperature?

[I mean, even if tek messed up a little bit in their heat calculations,
it isn't going to ever get that hot while *you* are using your scope.]

Food for thought.

-Chuck Harris

peter bunge wrote:
Thanks Siggi and Chuck, I have been printing the 2467B manual I bought
from
Artekmedia. I hate working from a computer screen and like to have paper
to
highlight or write notes on. I will check the A5 capacitors and am
reading
the manual.
I bought a spare horizontal chip and sequencer chip on Ebay and, because
the guy seemed to know about these problems asked about my issues. Here,
with his permission, are his replies through Ebay's limited messages. I
have not edited his English which I'm sure is much better than my
rendition
of his language. I am very fortunate to have stumbled on this source of
knowledge. (I bought the chips for a dead 2465, not my 2467B)

Hi Peter!

Many thanks for your purchases and for repeated customer.

To answer on your questions, I might not have more knowledge than yours,
I
developed some experience about these magnificent scopes when I did some
work on them long time time ago, I learned some but I don’t know the most
of it, I sold all of them and kept one 2465B and some spare parts that I
put them for sale here, any regarding the problem you have I don’t think
the U650 is the one because I had the same problem before...

...and I found the problem coming from some leaking SMD electrolytic caps
on the controller board, they are 4 of them there need to be replaced, I
did it then the screen came back to work correctly, other thing, they are
more of electrolytic caps on the main board need to be checked, they are
all aged more 20 years, but the one in the mentioned they go bad often,
other thing make sure if any cold solder somewhere in any part by using a
pencil and touch parts feet here and there........

You never know you can find one cold solder somewhere, other important
thing, you need to check all electrolytic caps in the main power supply,
some go bad often too, check if any acid leaks or swollen cap, these are
the first thing you need to do, other easy way I use to do, I use to have
multiple scopes 2465s so I keep swap the hybrid ICs until I find one is
bad, especially the vertical IC and Zaxis go bad faster than others the
2465 and 2467 have the same hybrid modules, you can do it....

As you mentioned the memory battery 🔋, it doesn’t have anything to do
with
your problem because when the battery goes bad or low in power the stored
calibration data will vanished then you will have a serious problem, you
will start to see on the screen in the place of readout lines like this
???????????????, so you need to replace the battery by new one and you
need
to recalibrate your scope again, these scopes have more than 20 years in
their lives........

So it is time to replace the battery before you loose the stored
calibration data, if you know how to do it then do now to avoid any
future
calibration problem.

Regarding the question about 0244-00 or 0244-01 if any difference, I
think
they are the same with a little bit of changes from the manufacturer, 00
is
the earlier 01 is the later but they have the same pin out and work the
same too.

Once I had a talk with the engineer who developed the 2465, it was a
quiet
honor to talk to him.....

I did ask him about about a problem o had, the screen was acting
erratically and sometimes go away, I swapped all the modules, checked
every
part, but I couldn’t find it, he right a way told me check a coil with 4
feet near by the Zaxis vertical maybe, he said one of the foot has cold
solder, I was shocked he was right !! I resolder it and worked fine, and
I
did ask hi about the U800 problems too, it is a customs complex IC they
go
bad over time because of excessive heat, he said when......

He said when we created this IC they didn’t know it will get hot 🥵 and
they didn’t design it with a socket to be easy to replace it without
damaging the PCB, he said by the time the IC started to fail over time it
was to late to redesign it with socket because the production line of
this
scope cane to end, he advices me to add a socket to it if I want to and
to
add a heat sink on top to reduce the heat and the IC will last longer,
but
make sure the heat sink don’t connect the 2 screws together…

Because the 2 screws that hold the U800 one of them has positive voltage,
so avoid to screw a heat sink on both screws, just one side and other
screw
left alone to avoid to short it, there is an article online showing how
to
add a heat sink to U800 safely.

I hope I gave you some hints that can help you, if you have more
questions
just ask and thanks for your purchases….

Oh I forgot to answer your question regarding how to remove the U800,
well,
back then I used a pump with heated tip in one piece, i desoldered one
foot
after another and make sure the foot is clear, and then after I finish
all
I put a flat screw driver underneath of the IC and try to push up
slowly, I
don’t force it, if it doesn’t move up I will go back and see if any foot
still not cleared, it is a difficult task and slow but it is better to be
in safe mode than damage the IC or PCB….

Now I have a much better electric pump desolder gun with controlled
temperature, it does a very good job and faster with safe temperature.

Good luck


On Sat, Nov 30, 2019 at 4:20 AM Siggi <siggi@undo.com> wrote:

The comparator U2510, an LM311, is used to compare the DAC output to pot
readings, and the MPU uses this with successive approximation to make a
software ADC. This is described in the “Theory of Operation” section.

The trigger hybrid is not involved in pot scanning, though otherwise it
works the way Chuck describes it.

On Sat, Nov 30, 2019 at 04:49 Chuck Harris <cfharris@erols.com> wrote:

There is no ADC part in the 2465 family scopes.

There is a DAC that is used as a part of an ADC
that is made from the DAC, CPU, MUX's, Sample and
Hold cells, and the trigger hybrid. The trigger
hybrid is used as the comparator that compares the
DAC output to the pot's wiper voltage.

The voltages get to the trigger hybrid by way of
a pair of muxes.

The capacitors referred to in the post are on the
A5 controller card on scopes with serial numbers
greater than B049999.

They are ordinary power supply bypass capacitors,
that because of the abuse of their being soldered
to the board by an oven, leak electrolyte all over
themselves, and the circuit board. The electrolyte
is highly corrosive to copper, and highly conductive
to electricity. It eats the copper traces, and
shorts out other components and traces.

They are the only surface mount electrolytic capacitors
on the board. Three are near the DAC, and the other is
on a distant corner.

If your A5 controller board has these capacitors, you
must replace them before anything else the scope does
will make much sense... Assuming that they haven't been
replaced already.

-Chuck Harris



peter bunge wrote:
Thanks Chuck, I was following the signal path from the two Intensity
pots
on the 2467B schematic, sheets 5 and 2. They do not go to an ADC input
but
I'm sure they must. There is something missing on the schematic, and I
have
looked at several.
Do you know what capacitors are referred to in this post:
Did you solve the capacitor leak problem on A5 logic board? Cause all
settings are under dependance of the DAC and when resistor connections
are
corroded everything goes wrong, including display points appearing,
and
intensity dimming.










Bob Koller <testtech@...>
 

On Sun, Dec 1, 2019 at 12:01 PM, peter bunge wrote:


"The symptoms are that changes in either of the intensity pots takes
several, and up to many (30 or more), seconds to respond either in
intensity on the screen, or voltages at the sequencer pins. Without
touching anything on the 'scope the 'trace turn off' counts down from
minutes, to 59 seconds, down to 2 seconds, then starts again at (8) minutes
without shutting off the display. So that feature is not working. At very
bright it did drop the intensity after 30 seconds but did not turn it off
so it may be partly working. I remember it turned the displays off until a
knob was moved.
Delta v and delta t are erratic placing the dotted lines on the screen, and
dt sometime shows dv lines or nothing. And they have the same sluggish
delay to doing anything."
This is interesting, do the Position controls exhibit similar laggy behavior?

I have a 2465B control board that does something similar; all the analog controls are much slower to respond than a normally operating instrument.
It passes self test, and works normally other that the very laggy and jumpy response to control changes.


Mlynch001
 

A whole lot of what you read on the internet about repairs
is very specific to a single one time failure/repair, that someone,
thought to document. That repair is then amplified, by the
megaphone that is the internet, to the stature of a legend, lore,
or meme . . . . . .<<

Chuck,

I do not have a 2465 scope, but I always like to read your replies, since I know I will very likely glean a piece of valuable knowledge from them. Thanks for saying things that need to be said, but which sometimes are not popular to hear. I'm pretty green when compared to most on this forum. Sadly, I have fallen for these very type of "internet or You Tube 'expert' advice", instead of relying on my instincts, my observations, the manual information and what I know to be true. I fear that many of such "problems" are ones that have been created or exacerbated by persons who make simple (i.e. "uninformed") mistakes and escalate problems, exactly as you have described. The old carpenter's adage of "measure twice and cut once" is applicable to our hobby/profession. I have personally turned more than one 'molehill' into a 'mountain'. One of my favorites is never "assume" because it makes an "ass out of u and me", ask me how I know! As always, I appreciate your very insightful and well reasoned posts.

--
Michael Lynch
Dardanelle, AR


peter bunge
 

Yes they are 'sticky' especially if I move ch2 then ch1. Also the digital
display of the DC trigger point is sluggish and often does not change with
the +/- level knob. It acts like a delay to the ADC which is not a
component but a complex group.
It could be a sluggish DAC U2101 sending to the sequencer via U2530 and U
2630 but I can't understand how (Analog Control tab 2). I am about to
'scope them. It is interesting that there is signs of work done around the
DAC, perhaps a broken trace but it is difficult to tell hence 'scoping to
look for a suspicious signal to follow. It could be an address line
floating but I would expect more problems. They look clean. pins 19 & 18
look messy but they are current O/P so look at U2630 pins 3 and 12. The
voltage here does not follow the intensity pots but is delayed. It jumps
suddenly but is clean. Moving on......
Peter.

On Sun, Dec 1, 2019 at 3:35 PM Bob Koller via Groups.Io <testtech=
yahoo.com@groups.io> wrote:

On Sun, Dec 1, 2019 at 12:01 PM, peter bunge wrote:


"The symptoms are that changes in either of the intensity pots takes
several, and up to many (30 or more), seconds to respond either in
intensity on the screen, or voltages at the sequencer pins. Without
touching anything on the 'scope the 'trace turn off' counts down from
minutes, to 59 seconds, down to 2 seconds, then starts again at (8)
minutes
without shutting off the display. So that feature is not working. At very
bright it did drop the intensity after 30 seconds but did not turn it off
so it may be partly working. I remember it turned the displays off until
a
knob was moved.
Delta v and delta t are erratic placing the dotted lines on the screen,
and
dt sometime shows dv lines or nothing. And they have the same sluggish
delay to doing anything."
This is interesting, do the Position controls exhibit similar laggy
behavior?

I have a 2465B control board that does something similar; all the analog
controls are much slower to respond than a normally operating instrument.
It passes self test, and works normally other that the very laggy and
jumpy response to control changes.




peter bunge
 

The Trig Level goes through a different Mux to the Intensity and position
controls. The three Mux O/Ps are joined and feed comparator LM311 U2510
(all on Tab 2 schematic) The Mux O/Ps (TP9) are clean and jump when a pot
is suddenly turned, the same for the comparator O/P. I am trying to find
something common to the Position, Trig Level, and Intensity Pots. The
comparator O/P goes through U2220 and it seems to respond immediately to
pot changes. Then there is the dv and dt switches that seldom work and when
they do the dotted lines are jumpy when moved with the pots below the
switches.
I assume the various positions are saved in RAM (the NOVRAM). Could it be
getting slow because of a low battery?
Is there a quick check I can make?

On Sun, Dec 1, 2019 at 5:39 PM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

Yes they are 'sticky' especially if I move ch2 then ch1. Also the digital
display of the DC trigger point is sluggish and often does not change with
the +/- level knob. It acts like a delay to the ADC which is not a
component but a complex group.
It could be a sluggish DAC U2101 sending to the sequencer via U2530 and U
2630 but I can't understand how (Analog Control tab 2). I am about to
'scope them. It is interesting that there is signs of work done around the
DAC, perhaps a broken trace but it is difficult to tell hence 'scoping to
look for a suspicious signal to follow. It could be an address line
floating but I would expect more problems. They look clean. pins 19 & 18
look messy but they are current O/P so look at U2630 pins 3 and 12. The
voltage here does not follow the intensity pots but is delayed. It jumps
suddenly but is clean. Moving on......
Peter.

On Sun, Dec 1, 2019 at 3:35 PM Bob Koller via Groups.Io <testtech=
yahoo.com@groups.io> wrote:

On Sun, Dec 1, 2019 at 12:01 PM, peter bunge wrote:


"The symptoms are that changes in either of the intensity pots takes
several, and up to many (30 or more), seconds to respond either in
intensity on the screen, or voltages at the sequencer pins. Without
touching anything on the 'scope the 'trace turn off' counts down from
minutes, to 59 seconds, down to 2 seconds, then starts again at (8)
minutes
without shutting off the display. So that feature is not working. At
very
bright it did drop the intensity after 30 seconds but did not turn it
off
so it may be partly working. I remember it turned the displays off
until
a
knob was moved.
Delta v and delta t are erratic placing the dotted lines on the screen,
and
dt sometime shows dv lines or nothing. And they have the same sluggish
delay to doing anything."
This is interesting, do the Position controls exhibit similar laggy
behavior?

I have a 2465B control board that does something similar; all the analog
controls are much slower to respond than a normally operating instrument.
It passes self test, and works normally other that the very laggy and
jumpy response to control changes.






peter bunge
 

My reasoning that the NOVRAM is causing the delayed response to the pots is
that maybe it is marginal at writing but OK at reading with low battery.
Anyway it should be replaced.
What is a good replacement?
Are the ones listed from China and Hong Kong OK to use?
How do I know if the battery is good in a "new" one?
What programmer is good to use?

On Sun, Dec 1, 2019 at 7:48 PM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

The Trig Level goes through a different Mux to the Intensity and position
controls. The three Mux O/Ps are joined and feed comparator LM311 U2510
(all on Tab 2 schematic) The Mux O/Ps (TP9) are clean and jump when a pot
is suddenly turned, the same for the comparator O/P. I am trying to find
something common to the Position, Trig Level, and Intensity Pots. The
comparator O/P goes through U2220 and it seems to respond immediately to
pot changes. Then there is the dv and dt switches that seldom work and when
they do the dotted lines are jumpy when moved with the pots below the
switches.
I assume the various positions are saved in RAM (the NOVRAM). Could it be
getting slow because of a low battery?
Is there a quick check I can make?

On Sun, Dec 1, 2019 at 5:39 PM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

Yes they are 'sticky' especially if I move ch2 then ch1. Also the digital
display of the DC trigger point is sluggish and often does not change
with
the +/- level knob. It acts like a delay to the ADC which is not a
component but a complex group.
It could be a sluggish DAC U2101 sending to the sequencer via U2530 and U
2630 but I can't understand how (Analog Control tab 2). I am about to
'scope them. It is interesting that there is signs of work done around
the
DAC, perhaps a broken trace but it is difficult to tell hence 'scoping to
look for a suspicious signal to follow. It could be an address line
floating but I would expect more problems. They look clean. pins 19 & 18
look messy but they are current O/P so look at U2630 pins 3 and 12. The
voltage here does not follow the intensity pots but is delayed. It jumps
suddenly but is clean. Moving on......
Peter.

On Sun, Dec 1, 2019 at 3:35 PM Bob Koller via Groups.Io <testtech=
yahoo.com@groups.io> wrote:

On Sun, Dec 1, 2019 at 12:01 PM, peter bunge wrote:


"The symptoms are that changes in either of the intensity pots takes
several, and up to many (30 or more), seconds to respond either in
intensity on the screen, or voltages at the sequencer pins. Without
touching anything on the 'scope the 'trace turn off' counts down from
minutes, to 59 seconds, down to 2 seconds, then starts again at (8)
minutes
without shutting off the display. So that feature is not working. At
very
bright it did drop the intensity after 30 seconds but did not turn it
off
so it may be partly working. I remember it turned the displays off
until
a
knob was moved.
Delta v and delta t are erratic placing the dotted lines on the
screen,
and
dt sometime shows dv lines or nothing. And they have the same
sluggish
delay to doing anything."
This is interesting, do the Position controls exhibit similar laggy
behavior?

I have a 2465B control board that does something similar; all the
analog
controls are much slower to respond than a normally operating
instrument.
It passes self test, and works normally other that the very laggy and
jumpy response to control changes.








Bob Koller <testtech@...>
 

My instrument has a new NVRAM, I routinely replace the Maxim/Dallas part with the less expensive ST M48Z08 part.
The new, or the old, NVRAM make no difference with the sluggish or sticky control action.

It seems to me that the uP is busy with something else, but what?
This instrument is a B05+ s/n, with the readout integrated on the control board. I wonder if there is some problem there, perhaps causing extra uP load?


peter bunge
 

Thanks Bob, that eliminates another potential cause. It seemed like a
reasonable cause that the new values were not being saved and old values
were being used. What do you think of the " Did you try cleaning the
contacts on the old U950 and re-insert it?" suggestion from Siggi? I hate
to disturb it. Have you tried this? I wonder where it fits in? It does not
seem to be in the ADC or CPU loop to be able to delay any signal updates
like the Trig Level display. Is your Trig Level digital display delayed?
My 2467B was fine one day then started acting up.
Delayed Trig Level display. However the trigger point responds immediately
as I move up the leading edge of the calibrator signal (20nS/div). It just
does not get updated on the CRT readout, or takes seconds to update.
Delayed Intensity adjustments. Time-out no longer works properly.
Posn response sluggish, horiz and all vertical.
My dV and dt switches often remember the last one pressed (dV gives the two
horizintal dotted lines, then dV to turn them off. Now dt brings them back
instead of two vertical dotted lines. Right now I can only get the
horizontal ones. I just pressed both and now I can't get either. Vertical
line suddenly appeared after many seconds. How are yours working?
These delayed dV and dt switch selections suggest the problem is not in the
ADC loop but just the digital values being delayed. Just thinking aloud on
the keyboard.
I will go away to read the manual for a bit.
Peter

On Mon, Dec 2, 2019 at 9:40 AM Bob Koller via Groups.Io <testtech=
yahoo.com@groups.io> wrote:

My instrument has a new NVRAM, I routinely replace the Maxim/Dallas part
with the less expensive ST M48Z08 part.
The new, or the old, NVRAM make no difference with the sluggish or sticky
control action.

It seems to me that the uP is busy with something else, but what?
This instrument is a B05+ s/n, with the readout integrated on the control
board. I wonder if there is some problem there, perhaps causing extra uP
load?