Date   

Re: Tek 576 Curve Tracer USB port to a cpu ... ?

Harvey White
 

You don't really need to worry a lot about it.

Use the arduino serial write to get the data to the PC.

Then in whatever program you use, be it pascal, visual basic, or what, open a com port for the data

You'll then get a data stream of what you've written.  I'd recommend ascii of the form

X= nnnn.nnnn; Y=nnnn.nnnn;

C has parse routines, other languages might.  There may be some nice tutorials out there.

For graphics, you can use things like write line, and then set pixel (mythical functions, depends on the language).

Short story is that it is possible to do.

Graphics are fairly easy once you see that you can write text anywhere on the screen, draw a line from point A to point B, and then plot a point (or draw a line from point A to B, depending on style).

The reason for doing it yourself is that you'll learn a lot, and that you can customize it to do exactly what you want.


Harvey

On 1/7/2020 5:05 PM, peter bunge wrote:
Getting the data digitized is the easy part. Can someone write the software
interface between the USB and the computer screen?
Arduinos and PICs probably have USB driver functions, its the graphics that
is the problem for me. I wish I had the skills.
I use a camera but the shutter speed needs to be long enough to avoid
bright patches of trace.
Tektronix at one time produced a digital camera to replace the Polaroid
ones but they went obsolete as fast as computers.

On Tue, Jan 7, 2020 at 4:29 PM Matthew Hofmann <mhofmann@sbcglobal.net>
wrote:

I have an old 575 like the one your brother has. I think I might do a
little exploration into the circuitry to see how one might drive a pair of
A/D converters to get the horiz & vert data.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Mlynch001
Sent: Tuesday, January 07, 2020 3:46 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek 576 Curve Tracer USB port to a cpu ... ?

On Tue, Jan 7, 2020 at 02:29 PM, Matthew Hofmann wrote:

I assume that the 576 Curve Tracer doesn't have a USB interface and this
guy
has somehow added one? Any idea how/where he tapped off of the 576 to
digitize the data on the CRT?
Matt,

Correct, No USB or other ports on the 576. It is from an age before USB
was even a dream. There is a person who has accomplished this, yes. Where
and How they tap in to get the data??? That is the $1 Million question,
one we would like to discover the answer to. There must be some way to do
it, but the cost of a commercial solution is steep. It is going to take
some deep knowledge of the 576 and whatever method provides the interface.
Some have suggested Arduino?
--
Michael Lynch
Dardanelle, AR







Re: 454 screen brightness issues?

Jack Ohme
 

I am fairly certain its the HV by this point, mike, since my -1960v is only
around 1800v. I meant the front panel intensity control with the touchy
wiper. I'm currently trying to ascertain the best way of getting a look
inside the HV circuitry, the 12KV multiplier for the anode seems to be on
top of the -2kv section for cathode and grid. I'm awful with loose parts so
I'd rather not tear the whole thing down, currently scouring the manual for
test points I could use to point out which diode or cap is bad in the bias
supply.

On Tue, Jan 7, 2020 at 2:36 PM Mike Dinolfo <mdinolfo@erols.com> wrote:

Jack, in response to your email of 1:33 pm:

I think it's possible that your "excessive trace brightness" problem
could be an issue with HV circuit component failure (as others have
suggested), and/or Z-axis circuitry or adjustment. I should also add
"and/or something else that I don't know". It's good that you've
managed to get +12V at TP1349, because I think this pretty much
indicates that the Z-axis circuitry is OK. But more on that below...

Regarding your resistance measurement: I believe that probably the
majority of "garden variety" multimeters in use today do not allow for
measurement of resistances in the 50 megohm range (they only indicate
"open circuit" or the equivalent of "no measurement possible"), but I
also believe most of the VTVM's of 50 or 60 years ago would do so.
Although a VTVM's accuracy and resolution for those measurements is only
fair, it would be sufficient for the measurement that I tried to
describe; that's why I suggested a VTVM. So your multimeter/ohmmeter
might be indicating "open circuit." But look at the schematic for the
454 CRT circuit and the Z-axis board and you will see the resistors
(R1442 thru R1449) that I mentioned; measuring from TP1349 (on the
Z-axis board) to CRT pin 3 is effectively a measurement of the
resistance across the terminals of C1449. Or you could do a "deep dive"
into the HV compartment (removing a few layers of components) and
measure the resistances individually. Note that I've never done such a
"deep dive"measurement, but I think I've seen emails from other
Tekscopes group members saying that a "power down" measurement of these
resistances might not be valid because the resistances could change
under applied voltages during "power up" conditions. It's also a lot of
work (my opinion) to do such a "deep dive" measurement, and even more
work to replace these components in a shotgun approach. So I've been
trying to encourage you to verify the Z-axis circuitry is OK before you
zero in on the HV circuitry as the culprit.

Regarding your "12V at the point" measurement: When doing the "Adjust
CRT Grid Bias" adjustment on page 6-11 of the manual, you have adjusted
INTENSITY to get +12 volts at TP1349, correct? When you then go to the
next step, to adjust CRT Grid Bias R1447, can you then reduce the
visible dot or trace on the screen to get it "turned down" to a
reasonable level of brightness? When you talk about "the pot" and "the
dial" and "8-10% of the pot's wiper", I admit that I'm confused as to
whether you are talking about the INTENSITY control (front panel) or
grid bias trimmer pot R1447.

Finally, my earlier emails did not correctly state the process described
on page 6-11 of the manual, and for that I apologize. But I'm kind of at
a dead end as far as any further suggestions.

Mike D N4MWP

On 1/7/20 1:33 PM, Jack Ohme wrote:
Mike-

My meter measures an open circuit from pin 3 to point 1349, I think the
resistance is more than it can measure. I was able to get 12v at the
point,
but its VERY touchy, about half of the pot does next to nothing, then the
middle changes so fast you have to brush the dial with your finger to
dial
in past 2 or 3 volts difference, then it becomes very slow again. So
about
20 volts of the 6.8v -> 32v transit occur on about 8-10% of the pot's
wiper
surface. Seems unusual to me, not the source of the problem at least, but
perhaps a clue. It just seems very odd to me that the CRT grid measures
within spec for the datasheet... actually about 25 volts more negative
than
its listed typical operating values at intensity pot centre. To the best
of
my understanding, a higher negative bias makes the screen darker, so this
is quite confusing indeed, and what led me to believe there may be a
busted
grid.

On Mon, Jan 6, 2020 at 8:10 PM Mike Dinolfo <mdinolfo@erols.com> wrote:

Jack:

In my previous email, I unsuccessfully tried to transcribe the procedure
for CRT grid bias adjustment described on page 6-11 of the manual. Grid
bias adjustment control R1447 does not directly affect the voltage at
TP1349. Refer to the manual (page 6-11) for the exact process; my
apologies for my error. I suggest the following:

1. Setup the scope's controls as described on page 6-8 and 6-9
"Preliminary Procedure".
2. Try to adjust the INTENSITY control to get +12V at TP1349, as per
page 6-11 "Adjust CRT Grid Bias." If this cannot be done, there might
be a Z-axis problem. If you can get +12 volts, then go to step 3 below:
3. Adjust CRT Grid Bias potentiometer R1447 per paragraph 6.d on page
6-11.
4. Let us know what the results are. Although at this point I might be
at a loss as to further ideas.

It's also possible that there might be an issue with the grid bias
resistors/potentiometer (R1442 thru R1449) as others have suggested. If
you have access to a ohmmeter (such as a VTVM) that can detect
variations of about 1.8 megohms in a total resistance of about 52
megohms, then you can check this by measuring the resistance (with power
down) from the CRT pin 3 to TP1349 while varying grid bias potentiometer
R1447 from fully CCW to fully CW. You might get one measured value with
the ohm meter's leads in one position, and another with the meter leads
"reversed"; if so then go with the higher set of measurements, as the
lower set of measurements would be due to forward bias of D1440.

Mike D N4MWP

On 1/6/20 7:37 PM, Jack Ohme wrote:
Mike,

I have a copy of the manual in PDF and on paper. The intensity dial
correctly changes the voltage (although the screen brightness shows no
change), but the grid biasing potentiometer does not change the voltage
at
TP1349, which stays at around 6.8v. I'm not sure whats happening here,
if
this is the grid biasing pot that is broken or something nearby on the
Z
axis board, but I will inspect the schematics. Let me know if you think
of
anything to look for.

-Jack

On Mon, Jan 6, 2020 at 2:15 PM Albert Otten <aodiversen@concepts.nl>
wrote:
Hi Jack,
Where should I be looking for those DC restorers, in the -1920v?
The 454 has no DC restorers. The HV transformer has separate windings
for
the grid and the cathode circuit. The rectified voltage for the grid
can be
reduced somewhat by the grid bias pot R1447 (in the divider chain with
R1442-R1446) and is stacked on the voltage supplied by the Z-axis
amplifier.
When you follow Mike's suggestion and use a pdf of the manual, you
will
note that the waveform at TP1349 is almost invisible. The blue picture
in
the paper manual is also very faint. The voltage switches between the
2
written values 17.7 V and 6.75 V.

Albert









Re: Tek 576 Curve Tracer USB port to a cpu ... ?

Ke-Fong Lin
 

I find it very surprising that the 576 doesn't have an X-Y output for a plotter.
These were common in the 60s-70s and I guess even in the 80s, before GPIB became common place.
For instance, my HP3580A spectrum analyzer has a 0-5V X-Y output with the related pen on-off outputs.
So you can have a nice spectrum plot on paper!
Maybe that's because Tek doesn't have a plotter offering (contrary to HP).
And there are various add-on to take photos of scope's screen.


Re: Tek 576 Curve Tracer USB port to a cpu ... ?

Mlynch001
 

The big advantage of the 576 is that it is solid state and the logic is TTL, so it may be easier to work directly with the ARDUINO than it might prove with the 575, just taking a guess on that . The one interface that I have seen not only exports the CRT Traces, but also the knob positions and voltages as well (on the 576 at least). The fact that the 576 contains that wonderful and complex readout card, might actually make the job easier to interface. I would be interested in such a project. I have a few ARDUINO boards lying around, looking for something to do. I think the ARDUINO code would be the hardest part, but what do I know.

--
Michael Lynch
Dardanelle, AR


Re: 454 screen brightness issues?

 

Jack, in response to your email of 1:33 pm:

I think it's possible that your "excessive trace brightness" problem
could be an issue with HV circuit component failure (as others have
suggested), and/or Z-axis circuitry or adjustment.  I should also add
"and/or something else that I don't know".  It's good that you've
managed to get +12V at TP1349, because I think this pretty much
indicates that the Z-axis circuitry is OK.  But more on that below...

Regarding your resistance measurement: I believe that probably the
majority of "garden variety" multimeters in use today do not allow for
measurement of resistances in the 50 megohm range (they only indicate
"open circuit" or the equivalent of "no measurement possible"), but I
also believe most of the VTVM's of 50 or 60 years ago would do so. 
Although a VTVM's accuracy and resolution for those measurements is only
fair, it would be sufficient for the measurement that I tried to
describe; that's why I suggested a VTVM.  So your multimeter/ohmmeter
might be indicating "open circuit."  But look at the schematic for the
454 CRT circuit and the Z-axis board and you will see the resistors
(R1442 thru R1449) that I mentioned; measuring from TP1349 (on the
Z-axis board) to CRT pin 3 is effectively a measurement of the
resistance across the terminals of C1449.  Or you could do a "deep dive"
into the HV compartment (removing a few layers of components) and
measure the resistances individually.  Note that I've never done such a
"deep dive"measurement, but I think I've seen emails from other
Tekscopes group members saying that a "power down" measurement of these
resistances might not be valid because the resistances could change
under applied voltages during "power up" conditions.  It's also a lot of
work (my opinion) to do such a "deep dive" measurement, and even more
work to replace these components in a shotgun approach.  So I've been
trying to encourage you to verify the Z-axis circuitry is OK before you
zero in on the HV circuitry as the culprit.

Regarding your "12V at the point" measurement: When doing the "Adjust
CRT Grid Bias" adjustment on page 6-11 of the manual, you have adjusted
INTENSITY to get +12 volts at TP1349, correct?  When you then go to the
next step, to adjust CRT Grid Bias R1447, can you then reduce the
visible dot or trace on the screen to get it "turned down" to a
reasonable level of brightness?  When you talk about "the pot" and "the
dial" and "8-10% of the pot's wiper", I admit that I'm confused as to
whether you are talking about the INTENSITY control (front panel) or
grid bias trimmer pot R1447.

Finally, my earlier emails did not correctly state the process described
on page 6-11 of the manual, and for that I apologize. But I'm kind of at
a dead end as far as any further suggestions.

Mike D N4MWP

On 1/7/20 1:33 PM, Jack Ohme wrote:
Mike-

My meter measures an open circuit from pin 3 to point 1349, I think the
resistance is more than it can measure. I was able to get 12v at the point,
but its VERY touchy, about half of the pot does next to nothing, then the
middle changes so fast you have to brush the dial with your finger to dial
in past 2 or 3 volts difference, then it becomes very slow again. So about
20 volts of the 6.8v -> 32v transit occur on about 8-10% of the pot's wiper
surface. Seems unusual to me, not the source of the problem at least, but
perhaps a clue. It just seems very odd to me that the CRT grid measures
within spec for the datasheet... actually about 25 volts more negative than
its listed typical operating values at intensity pot centre. To the best of
my understanding, a higher negative bias makes the screen darker, so this
is quite confusing indeed, and what led me to believe there may be a busted
grid.

On Mon, Jan 6, 2020 at 8:10 PM Mike Dinolfo <mdinolfo@erols.com> wrote:

Jack:

In my previous email, I unsuccessfully tried to transcribe the procedure
for CRT grid bias adjustment described on page 6-11 of the manual. Grid
bias adjustment control R1447 does not directly affect the voltage at
TP1349. Refer to the manual (page 6-11) for the exact process; my
apologies for my error. I suggest the following:

1. Setup the scope's controls as described on page 6-8 and 6-9
"Preliminary Procedure".
2. Try to adjust the INTENSITY control to get +12V at TP1349, as per
page 6-11 "Adjust CRT Grid Bias." If this cannot be done, there might
be a Z-axis problem. If you can get +12 volts, then go to step 3 below:
3. Adjust CRT Grid Bias potentiometer R1447 per paragraph 6.d on page
6-11.
4. Let us know what the results are. Although at this point I might be
at a loss as to further ideas.

It's also possible that there might be an issue with the grid bias
resistors/potentiometer (R1442 thru R1449) as others have suggested. If
you have access to a ohmmeter (such as a VTVM) that can detect
variations of about 1.8 megohms in a total resistance of about 52
megohms, then you can check this by measuring the resistance (with power
down) from the CRT pin 3 to TP1349 while varying grid bias potentiometer
R1447 from fully CCW to fully CW. You might get one measured value with
the ohm meter's leads in one position, and another with the meter leads
"reversed"; if so then go with the higher set of measurements, as the
lower set of measurements would be due to forward bias of D1440.

Mike D N4MWP

On 1/6/20 7:37 PM, Jack Ohme wrote:
Mike,

I have a copy of the manual in PDF and on paper. The intensity dial
correctly changes the voltage (although the screen brightness shows no
change), but the grid biasing potentiometer does not change the voltage
at
TP1349, which stays at around 6.8v. I'm not sure whats happening here, if
this is the grid biasing pot that is broken or something nearby on the Z
axis board, but I will inspect the schematics. Let me know if you think
of
anything to look for.

-Jack

On Mon, Jan 6, 2020 at 2:15 PM Albert Otten <aodiversen@concepts.nl>
wrote:
Hi Jack,
Where should I be looking for those DC restorers, in the -1920v?
The 454 has no DC restorers. The HV transformer has separate windings
for
the grid and the cathode circuit. The rectified voltage for the grid
can be
reduced somewhat by the grid bias pot R1447 (in the divider chain with
R1442-R1446) and is stacked on the voltage supplied by the Z-axis
amplifier.
When you follow Mike's suggestion and use a pdf of the manual, you will
note that the waveform at TP1349 is almost invisible. The blue picture
in
the paper manual is also very faint. The voltage switches between the 2
written values 17.7 V and 6.75 V.

Albert






Re: Hakko FR-301 alternatives?

Mlynch001
 

I am cheap, so I took a chance on a CCC (Cheap Chinese Crap) ZD-985 Vacuum desolder station @ about $119.00 (about 2 years ago) delivered in 2 days. Amazon has a great return policy, so when I got it, I immediately started cleaning components off of old boards, for practice and as a "stress test". Figuring that this thing would throw craps in an hour or two, I was greatly surprised! The thing came through with flying colors. No return needed. That was almost two years ago, it still works great. I am not sure how much solder this thing has removed, but the gun has been cleaned many times with large globs of solder being removed from the gun each time. The ZD-985 also came with a bunch of extra parts, tips and filters. The only parts needed, so far, are the little filters that go inside the gun. For a cheap alternative, this thing is more than acceptable. It sure beats solder sick, manual solder suckers and the like. Much less likely to damage a precious board with this tool. Is it equal to a genuine HAKKO? I doubt it. Is it 90-95% of what a HAKKO is? I say it is for me and I have $200+ in my bank account as a result. The sad thing is that some HAKKO products or components are being sourced in China, and ruthlessly counterfeited there as well.

--
Michael Lynch
Dardanelle, AR


Re: Tek 576 Curve Tracer USB port to a cpu ... ?

Eric
 

Arduinos can dump serial stream data direct in to a pc the micro can handle
all the pc interconnect as well.

On Tue, Jan 7, 2020, 5:05 PM peter bunge <bunge.pjp@gmail.com> wrote:

Getting the data digitized is the easy part. Can someone write the software
interface between the USB and the computer screen?
Arduinos and PICs probably have USB driver functions, its the graphics that
is the problem for me. I wish I had the skills.
I use a camera but the shutter speed needs to be long enough to avoid
bright patches of trace.
Tektronix at one time produced a digital camera to replace the Polaroid
ones but they went obsolete as fast as computers.

On Tue, Jan 7, 2020 at 4:29 PM Matthew Hofmann <mhofmann@sbcglobal.net>
wrote:

I have an old 575 like the one your brother has. I think I might do a
little exploration into the circuitry to see how one might drive a pair
of
A/D converters to get the horiz & vert data.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Mlynch001
Sent: Tuesday, January 07, 2020 3:46 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek 576 Curve Tracer USB port to a cpu ... ?

On Tue, Jan 7, 2020 at 02:29 PM, Matthew Hofmann wrote:


I assume that the 576 Curve Tracer doesn't have a USB interface and
this
guy
has somehow added one? Any idea how/where he tapped off of the 576 to
digitize the data on the CRT?
Matt,

Correct, No USB or other ports on the 576. It is from an age before USB
was even a dream. There is a person who has accomplished this, yes.
Where
and How they tap in to get the data??? That is the $1 Million question,
one we would like to discover the answer to. There must be some way to
do
it, but the cost of a commercial solution is steep. It is going to take
some deep knowledge of the 576 and whatever method provides the
interface.
Some have suggested Arduino?
--
Michael Lynch
Dardanelle, AR









Re: 2235 2mV vertical range noise and surprising fixes

Panos
 

On Tue, Jan 7, 2020 at 11:00 PM, walter shawlee wrote:


replace any bad switching rectifiers if needed.
Hello Mr Walter,
can you be more specific with the bad rectifiers please. If I understand correctly you mean that in some cases someone can find a partially bad rectifier?

Panos.


Re: Tek 576 Curve Tracer USB port to a cpu ... ?

peter bunge
 

Getting the data digitized is the easy part. Can someone write the software
interface between the USB and the computer screen?
Arduinos and PICs probably have USB driver functions, its the graphics that
is the problem for me. I wish I had the skills.
I use a camera but the shutter speed needs to be long enough to avoid
bright patches of trace.
Tektronix at one time produced a digital camera to replace the Polaroid
ones but they went obsolete as fast as computers.

On Tue, Jan 7, 2020 at 4:29 PM Matthew Hofmann <mhofmann@sbcglobal.net>
wrote:

I have an old 575 like the one your brother has. I think I might do a
little exploration into the circuitry to see how one might drive a pair of
A/D converters to get the horiz & vert data.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Mlynch001
Sent: Tuesday, January 07, 2020 3:46 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek 576 Curve Tracer USB port to a cpu ... ?

On Tue, Jan 7, 2020 at 02:29 PM, Matthew Hofmann wrote:


I assume that the 576 Curve Tracer doesn't have a USB interface and this
guy
has somehow added one? Any idea how/where he tapped off of the 576 to
digitize the data on the CRT?
Matt,

Correct, No USB or other ports on the 576. It is from an age before USB
was even a dream. There is a person who has accomplished this, yes. Where
and How they tap in to get the data??? That is the $1 Million question,
one we would like to discover the answer to. There must be some way to do
it, but the cost of a commercial solution is steep. It is going to take
some deep knowledge of the 576 and whatever method provides the interface.
Some have suggested Arduino?
--
Michael Lynch
Dardanelle, AR







Re: Hakko FR-301 alternatives?

KB6NAX
 

Bert, my drum beats hail and hearty for anyone who can do a job with el-cheapo tools and the results are no different than using the super expensive "I wanna have one too" tools. I jest a bit but over the years I gave up on the idea of owning a de-soldering gun for one simple reason: With all of the garbage I work on all sorts of stuff gets into the suction channel, shards of oxidized solder, charred wire insulation, and flux ash. Taking time and effort to clean out the suction channel and emptying the collection cartridge was time wasted. If I constantly worked on circuit boards alone a gun would be great to have. So it's solder wick, hand desoldering pump, poking through clogged plated through holes, draining solder off of overloaded terminals, etc. So to have a big clunker taking up space on my work bench is a non option. Repairing and replacing damaged pads, often from previous rework, is all part of the job. -Arden


Re: Tek 576 Curve Tracer USB port to a cpu ... ?

Matthew Hofmann
 

I have an old 575 like the one your brother has. I think I might do a little exploration into the circuitry to see how one might drive a pair of A/D converters to get the horiz & vert data.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Mlynch001
Sent: Tuesday, January 07, 2020 3:46 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek 576 Curve Tracer USB port to a cpu ... ?

On Tue, Jan 7, 2020 at 02:29 PM, Matthew Hofmann wrote:


I assume that the 576 Curve Tracer doesn't have a USB interface and this guy
has somehow added one? Any idea how/where he tapped off of the 576 to
digitize the data on the CRT?
Matt,

Correct, No USB or other ports on the 576. It is from an age before USB was even a dream. There is a person who has accomplished this, yes. Where and How they tap in to get the data??? That is the $1 Million question, one we would like to discover the answer to. There must be some way to do it, but the cost of a commercial solution is steep. It is going to take some deep knowledge of the 576 and whatever method provides the interface. Some have suggested Arduino?
--
Michael Lynch
Dardanelle, AR


2235 2mV vertical range noise and surprising fixes

 

The 2mV vertical range on the 2235 is a triumph of marketing over technology, as it really pushes the performance of the scope to a place where it doesn't willingly want to go. virtually all 2235's exhibit increasing noise on this range as they age, and sometimes the displayed noise is huge (when the psu caps deteriorate in the secondary of the switching supply).

I have had to fix many of these, and generally follow this plan:
----------------------------------------------------------------------------------
1. replace all LV psu secondary caps with modern low ESR versions (820uf becomes 1000uf).
check for ripple after the change at the psu test points, and replace any bad switching rectifiers if needed.
2. tighten all ground hardware all over the scope, especially around the vertical assembly. make sure all case ground screws (2) are there too.

Recently I had one stubborn unit that just wouldn't behave even after re-capping (which it desperately needed), and I traced the fault to a very unusual area. all of the switching supplies are slaved the the adjustment of the -8.6V level. my unit measured -8.42V, which I initially ignored as it seemed to be within spec. BUT, the manual specifies a tighter adjustment range, and incredibly, as I raised the voltage to just over -8.6V with the rear edge trimpot on the motherboard, the displayed ripple almost vanished. I have never seen this interaction before, so I thought I would pass it on, as it may prove useful to anybody re-capping one of these nice little 100MHz scopes.

the difference between good and bad ripple display is a very narrow -8.6V adjustment range, about 150mV, which I found amazing, as I cannot see how this has such a dramatic effect, but it does. no adjustment or parts replacement can totally remove ALL ripple from the 2mV range display, but you can certainly improve it down to about one minor division. bad scopes with poor caps can be 5-10 minor divisions, making it unusable on the 2, 5 and 10mV ranges.

I hope this proves useful to others working on 2235's.
all the best,
walter (walter2@sphere.bc.ca)
sphere research corp.
https://www.sphere.bc.ca/test/index.html


Re: 454 screen brightness issues?

Albert Otten
 

Hi Jack,

I had my leads wrong, the grid is actually around
150 volts ABOVE the cathode, which explains everything. Thank God it isn't
a broken grid, but... the Z axis board is certainly messed up if something
like this is going on.
Now that you confirm that you made a sign mistake (question in my previous response) the fault is certainly not in the Z-axis board, diagram <16>, or in the CRT itself. In y opinion it must be a fault in the CRT supply circuitry diagram <17>. Probably in the grid supply. Probably an open "bottom" end of the grid bias pot R1447. Did you measure the resistance between wiper and joint of R1447/D1440? Does it go to zero in one detend of the wiper?

Albert


Re: How to record the calibration parameters of a 2465BDM to whatever memory device. & Perhaps a sea-relig! 2465 and what to do.

Tom Gardner
 

On 07/01/20 19:17, Panos wrote:
On Tue, Jan 7, 2020 at 08:27 PM, Tom Gardner wrote:

As a fallback, take a video.....
Yes Tom I know, but unfortunately is useful only if you have a GPIB option on your oscilloscope and very very patience to work with this.
If you have the information, you can find a way of using an external programmer to put the info into the new ic.

The GPIB is not necessary.

But even then, if/when the earom lost a constant, this is a sign that it has come its end of life and need to replace.
You have to proactively capture the contents before any part of it is lost!


Re: Tek 576 Curve Tracer USB port to a cpu ... ?

Mlynch001
 

On Tue, Jan 7, 2020 at 02:29 PM, Matthew Hofmann wrote:


I assume that the 576 Curve Tracer doesn't have a USB interface and this guy
has somehow added one? Any idea how/where he tapped off of the 576 to
digitize the data on the CRT?
Matt,

Correct, No USB or other ports on the 576. It is from an age before USB was even a dream. There is a person who has accomplished this, yes. Where and How they tap in to get the data??? That is the $1 Million question, one we would like to discover the answer to. There must be some way to do it, but the cost of a commercial solution is steep. It is going to take some deep knowledge of the 576 and whatever method provides the interface. Some have suggested Arduino?
--
Michael Lynch
Dardanelle, AR


Re: Hakko FR-301 alternatives?

12ax7
 

Hi Dave,

Not sure if your question is directed my way. The FR300 has 3 controls, 1) an on/off switch to heat up or turn off the gun, 2) a temperature dial, and 3) a trigger to engage the vacuum when you desolder.

I got my manual from the internet. There are a number of pretty good Youtube videos, including some directly from Hakko on how to use the FR300/301. As George L says above ... it has great build quality and is a breeze to maintain and use. You can see that in the Youtube videos.

I would also recommend buying one of the holders/stands for the gun. The "chopstick stand" that comes with the device is ok, but after a while you'll likely get frustrated having the "hot" gun laying down on its side and in the way.

Jeff


Re: Tek 576 Curve Tracer solid state replacement for relays ?

KB6NAX
 

I have no knowledge of the 576 circuits but it is conceivable if the voltages are within limits an analog transmission gate could replace an electro-mechanical relay. Of course the "on" resistance would be not less than tens of ohms and could be in the 100's so the gate has to drive a very high resistance load to minimize errors. An example of a commonly found transmission gate is the CD4066. Looks like replacing bad with good relays is the best remedy for the 576. -Arden


Re: Tek 576 Curve Tracer USB port to a cpu ... ?

Matthew Hofmann
 

I assume that the 576 Curve Tracer doesn't have a USB interface and this guy has somehow added one? Any idea how/where he tapped off of the 576 to digitize the data on the CRT?

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of garp66
Sent: Monday, January 06, 2020 5:11 PM
To: TekScopes@groups.io
Subject: [TekScopes] Tek 576 Curve Tracer USB port to a cpu ... ?

hi,

Has anyone thought of interfacing a Tek 576 Curve Tracer (Or any of the other Tek Curve Tracers) to a laptop via USB ?

I have been thinking of putting an Arduino or Rasp Pi inside a Tek 576, with a few A/D & D I/O shields to get the data out for comparisons and automated measurements.

I just saw this YouTube Demo of a "pricy" USB conversion :
(dated Jan 30, 2019)

https://www.youtube.com/watch?v=LSMqD5iwj4U

done by Tuntien of
https://equiptek.com/000.htm

rick


Re: Tek 576 Curve Tracer solid state replacement for relays ?

DaveH52
 

On Mon, Jan 6, 2020 at 05:01 PM, garp66 wrote:


Tek 576
I'm sure it could be done, however, you'd need to use some sort of isolator-gate-driver for each set of contacts you want to replace. Such devices do exist.
https://www.analog.com/en/products/interface-isolation/isolation/isolated-gate-drivers.html#
but it might be easier to find relays that will fit the same footprint.


Re: 454 screen brightness issues?

Jack Ohme
 

Update, everyone

I am a complete idiot. I had my leads wrong, the grid is actually around
150 volts ABOVE the cathode, which explains everything. Thank God it isn't
a broken grid, but... the Z axis board is certainly messed up if something
like this is going on. I will further consult schematics, if anyone knows
what might be wrong, drop me a line

On Tue, Jan 7, 2020 at 10:33 AM Jack Ohme via Groups.Io <machinamancerjack=
gmail.com@groups.io> wrote:

Mike-

My meter measures an open circuit from pin 3 to point 1349, I think the
resistance is more than it can measure. I was able to get 12v at the point,
but its VERY touchy, about half of the pot does next to nothing, then the
middle changes so fast you have to brush the dial with your finger to dial
in past 2 or 3 volts difference, then it becomes very slow again. So about
20 volts of the 6.8v -> 32v transit occur on about 8-10% of the pot's wiper
surface. Seems unusual to me, not the source of the problem at least, but
perhaps a clue. It just seems very odd to me that the CRT grid measures
within spec for the datasheet... actually about 25 volts more negative than
its listed typical operating values at intensity pot centre. To the best of
my understanding, a higher negative bias makes the screen darker, so this
is quite confusing indeed, and what led me to believe there may be a busted
grid.

On Mon, Jan 6, 2020 at 8:10 PM Mike Dinolfo <mdinolfo@erols.com> wrote:

Jack:

In my previous email, I unsuccessfully tried to transcribe the procedure
for CRT grid bias adjustment described on page 6-11 of the manual. Grid
bias adjustment control R1447 does not directly affect the voltage at
TP1349. Refer to the manual (page 6-11) for the exact process; my
apologies for my error. I suggest the following:

1. Setup the scope's controls as described on page 6-8 and 6-9
"Preliminary Procedure".
2. Try to adjust the INTENSITY control to get +12V at TP1349, as per
page 6-11 "Adjust CRT Grid Bias." If this cannot be done, there might
be a Z-axis problem. If you can get +12 volts, then go to step 3 below:
3. Adjust CRT Grid Bias potentiometer R1447 per paragraph 6.d on page
6-11.
4. Let us know what the results are. Although at this point I might be
at a loss as to further ideas.

It's also possible that there might be an issue with the grid bias
resistors/potentiometer (R1442 thru R1449) as others have suggested. If
you have access to a ohmmeter (such as a VTVM) that can detect
variations of about 1.8 megohms in a total resistance of about 52
megohms, then you can check this by measuring the resistance (with power
down) from the CRT pin 3 to TP1349 while varying grid bias potentiometer
R1447 from fully CCW to fully CW. You might get one measured value with
the ohm meter's leads in one position, and another with the meter leads
"reversed"; if so then go with the higher set of measurements, as the
lower set of measurements would be due to forward bias of D1440.

Mike D N4MWP

On 1/6/20 7:37 PM, Jack Ohme wrote:
Mike,

I have a copy of the manual in PDF and on paper. The intensity dial
correctly changes the voltage (although the screen brightness shows no
change), but the grid biasing potentiometer does not change the voltage
at
TP1349, which stays at around 6.8v. I'm not sure whats happening here,
if
this is the grid biasing pot that is broken or something nearby on the
Z
axis board, but I will inspect the schematics. Let me know if you think
of
anything to look for.

-Jack

On Mon, Jan 6, 2020 at 2:15 PM Albert Otten <aodiversen@concepts.nl>
wrote:

Hi Jack,
Where should I be looking for those DC restorers, in the -1920v?
The 454 has no DC restorers. The HV transformer has separate windings
for
the grid and the cathode circuit. The rectified voltage for the grid
can be
reduced somewhat by the grid bias pot R1447 (in the divider chain with
R1442-R1446) and is stacked on the voltage supplied by the Z-axis
amplifier.
When you follow Mike's suggestion and use a pdf of the manual, you
will
note that the waveform at TP1349 is almost invisible. The blue picture
in
the paper manual is also very faint. The voltage switches between the
2
written values 17.7 V and 6.75 V.

Albert








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