Topics

2465A channel 2 problems

GerryR
 

A little history first: Acquired the 'scope recently and everything was working fine. Old battery dated 07-87. Decided to change battery and took all known precautions, but somehow screwed up and requires re-cal. I have attempted re-cal, and went from a "Test 04 Failed 04" to a "Test 04 failed 02" which is a limit failure. Channel 2 "calibrates" up to the 10V input (cal 02), and I get a Limit 130 error, no matter what I try, so I assume that is my problem. In the non-calibrate run mode, the channel 2 input only works up to the 500 mV range (Hi-Impedance input with co-ax) and with the 10X probe, up to 5V. The display range readout works, but in the 1V, 2V and 5V ranges, it appears to stay in the 100 mV, 200 mV and 500 mV ranges, so it appears the attenuator isn't switching properly.

Is there a way to tell whether it is the attenuator, or if the proper outputs are not getting to the drivers for the attenuator relays, or is this still a calibration problem? I have no way to monitor a "word" from the processor at this point. I did try monitoring channel 1 at the drivers and comparing them to channel 2, but found it difficult to get any meaningful data. Any help will be appreciated.
GerryR

 

How does Channel 2 work when using the scope in the "normal" mode?  If it seems about right (just not precisely calibrated) when measuring known voltages then the attenuator is switching.

On Wednesday, October 16, 2019, 03:31:47 PM CDT, GerryR <totalautomation1@...> wrote:

A little history first:  Acquired the 'scope recently and everything was working fine. Old battery dated 07-87.  Decided to change battery and took all known precautions, but somehow screwed up and requires re-cal.  I have attempted re-cal, and went from a "Test 04 Failed 04" to a "Test 04 failed 02" which is a limit failure.  Channel 2 "calibrates" up to the 10V input (cal 02), and I get a Limit 130 error, no matter what I try, so I assume that is my problem.  In the non-calibrate run mode, the channel 2 input only works up to the 500 mV range (Hi-Impedance input with co-ax) and with the 10X probe, up to 5V.  The display range readout works, but in the 1V, 2V and 5V ranges, it appears to stay in the 100 mV, 200 mV and 500 mV ranges, so it appears the attenuator isn't switching properly.

Is there a way to tell whether it is the attenuator, or if the proper outputs are not getting to the drivers for the attenuator relays, or is this still a calibration problem?  I have no way to monitor a "word" from the processor at this point.  I did try monitoring channel 1 at the drivers and comparing them to channel 2, but found it difficult to get any meaningful data.  Any help will be appreciated.
GerryR

GerryR
 

That's the problem, in the normal mode, the 1, 2 and 5 volt ranges are all off, for example, a 1V signal on the 1V per division scale, displays as if on the 100 mV scale, etc., so I am assuming the attenuator is not switching for those ranges, but don't know if the relays in the attenuator, or the logic telling which tells them to switch that is bad. The digital readout shows 1V on the 1V scale but the display of the wave is as if it is on the 100 mV scale.
Is there a list of digital words for the different scales or a way to tell if the logic is bad?

GerryR

----- Original Message -----
From: "machineguy59 via Groups.Io" <machineguy59=yahoo.com@groups.io>
To: <TekScopes@groups.io>
Sent: Wednesday, October 16, 2019 6:48 PM
Subject: Re: [TekScopes] 2465A channel 2 problems


How does Channel 2 work when using the scope in the "normal" mode? If it seems about right (just not precisely calibrated) when measuring known voltages then the attenuator is switching.
On Wednesday, October 16, 2019, 03:31:47 PM CDT, GerryR <totalautomation1@...> wrote:

A little history first: Acquired the 'scope recently and everything was working fine. Old battery dated 07-87. Decided to change battery and took all known precautions, but somehow screwed up and requires re-cal. I have attempted re-cal, and went from a "Test 04 Failed 04" to a "Test 04 failed 02" which is a limit failure. Channel 2 "calibrates" up to the 10V input (cal 02), and I get a Limit 130 error, no matter what I try, so I assume that is my problem. In the non-calibrate run mode, the channel 2 input only works up to the 500 mV range (Hi-Impedance input with co-ax) and with the 10X probe, up to 5V. The display range readout works, but in the 1V, 2V and 5V ranges, it appears to stay in the 100 mV, 200 mV and 500 mV ranges, so it appears the attenuator isn't switching properly.

Is there a way to tell whether it is the attenuator, or if the proper outputs are not getting to the drivers for the attenuator relays, or is this still a calibration problem? I have no way to monitor a "word" from the processor at this point. I did try monitoring channel 1 at the drivers and comparing them to channel 2, but found it difficult to get any meaningful data. Any help will be appreciated.
GerryR

GerryR
 

Another question or two for those in the know: At the beginning of the Cal 02 procedure, it states to connect a 0.5 V standard-amplitude signal to CH 1 and to use CH 2 Position to vertically position the "trace" to within 1 division of the center graticule line, and then to use the CH 1 Position and Volts/DIV VAR controls to obtain a 10-division horizontal signal. I don't get a "trace," only 2 dots. I can position the dots with the controls to put one dot on the first graticule line and the other on the 10th.
Question 1: "Is this "normal," or am I doing something wrong?" I've read and re-read the procedures and can't find any references to this.

Also, at the beginning of the Cal 01 procedure, it states that, "Upon entering Cal 01, the Input Coupling is automatically set to 50 ohm DC ....." This doesn't appear to be true for the other Cal procedures (2,3,4,etc), as I had to install a terminator on my generator to get the actual levels called out in the test procedures (monitored on another scope).
Question 2: "Is this correct, or am I missing something here, as well?

Thanks in advance for any input!

Gerry

------ Original Message -----
From: "machineguy59 via Groups.Io" <machineguy59=yahoo.com@groups.io>
To: <TekScopes@groups.io>
Sent: Wednesday, October 16, 2019 6:48 PM
Subject: Re: [TekScopes] 2465A channel 2 problems


How does Channel 2 work when using the scope in the "normal" mode? If it seems about right (just not precisely calibrated) when measuring known voltages then the attenuator is switching.
On Wednesday, October 16, 2019, 03:31:47 PM CDT, GerryR <totalautomation1@...> wrote:

A little history first: Acquired the 'scope recently and everything was working fine. Old battery dated 07-87. Decided to change battery and took all known precautions, but somehow screwed up and requires re-cal. I have attempted re-cal, and went from a "Test 04 Failed 04" to a "Test 04 failed 02" which is a limit failure. Channel 2 "calibrates" up to the 10V input (cal 02), and I get a Limit 130 error, no matter what I try, so I assume that is my problem. In the non-calibrate run mode, the channel 2 input only works up to the 500 mV range (Hi-Impedance input with co-ax) and with the 10X probe, up to 5V. The display range readout works, but in the 1V, 2V and 5V ranges, it appears to stay in the 100 mV, 200 mV and 500 mV ranges, so it appears the attenuator isn't switching properly.

Is there a way to tell whether it is the attenuator, or if the proper outputs are not getting to the drivers for the attenuator relays, or is this still a calibration problem? I have no way to monitor a "word" from the processor at this point. I did try monitoring channel 1 at the drivers and comparing them to channel 2, but found it difficult to get any meaningful data. Any help will be appreciated.
GerryR

Chuck Harris
 

Hi Gerry,

First, you are not supposed to get a trace, just a pair
of dots, approximately 10 divisions apart.

This is a crucial step, as it affects all future steps.

I would suggest that you always put it in VAR mode, as it
will always give you an adjustable range to hit the mark.

But note: It is most important that the VAR knob be back
in its click before you start the next, and all subsequent,
steps. If you do not do this, you will achieve out-of-range.

If you repeat this step after having done it recently, you
will usually find that the dots are perfectly spaced.

There is no linkage between the 50 ohm annunciator light and
the 50 ohm relay in the preamp. Unless your preamp is broken,
it is in 50 ohm mode.

As a test, when the scope is in normal mode, put the preamps
in 50 ohm mode, and measure them with an ohmmeter. If they
are other than 50 ohm, you have the ever popular burned out
50 ohm load. Unless you are very clever you will be replacing
your preamp, as the resistor is printed on the ceramic substrate.

-Chuck Harris

GerryR wrote:

Another question or two for those in the know: At the beginning of the Cal 02 procedure, it states to connect a 0.5 V standard-amplitude signal to CH 1 and to use CH 2 Position to vertically position the "trace" to within 1 division of the center graticule line, and then to use the CH 1 Position and Volts/DIV VAR controls to obtain a 10-division horizontal signal. I don't get a "trace," only 2 dots. I can position the dots with the controls to put one dot on the first graticule line and the other on the 10th.
Question 1: "Is this "normal," or am I doing something wrong?" I've read and re-read the procedures and can't find any references to this.

Also, at the beginning of the Cal 01 procedure, it states that, "Upon entering Cal 01, the Input Coupling is automatically set to 50 ohm DC ....." This doesn't appear to be true for the other Cal procedures (2,3,4,etc), as I had to install a terminator on my generator to get the actual levels called out in the test procedures (monitored on another scope).
Question 2: "Is this correct, or am I missing something here, as well?

Thanks in advance for any input!

Gerry

 

You should be able to hear the relays switch as you change scales.  That will indicate the logic is operating.  It is more likely the attenuator is dirty and the fingers don't make good contact on the ceramic substrate.  Cleaning is a delicate process to not break the ceramic or bend the contact fingers.  Sometimes you can clear the problem by spraying a contact cleaner into the attenuator.  But the best, long term solution is to open the attenuator and clean it, OR replace the attenuator.  Both are involved processes.

On Wednesday, October 16, 2019, 06:58:23 PM CDT, GerryR <totalautomation1@...> wrote:

That's the problem, in the normal mode, the 1, 2 and 5 volt ranges are all
off, for example, a 1V signal on the 1V per division scale, displays as if
on the 100 mV scale, etc., so I am assuming the attenuator is not switching
for those ranges, but don't know if the relays in the attenuator, or the
logic telling which tells them to switch that is bad.  The digital readout
shows 1V on the 1V scale but the display of the wave is as if it is on the
100 mV scale.
Is there a list of digital words for the different scales or a way to tell
if the logic is bad?

GerryR


----- Original Message -----
From: "machineguy59 via Groups.Io" <machineguy59=yahoo.com@groups.io>
To: <TekScopes@groups.io>
Sent: Wednesday, October 16, 2019 6:48 PM
Subject: Re: [TekScopes] 2465A channel 2 problems


How does Channel 2 work when using the scope in the "normal" mode? If it
seems about right (just not precisely calibrated) when measuring known
voltages then the attenuator is switching.
    On Wednesday, October 16, 2019, 03:31:47 PM CDT, GerryR
<totalautomation1@...> wrote:

A little history first: Acquired the 'scope recently and everything was
working fine. Old battery dated 07-87. Decided to change battery and took
all known precautions, but somehow screwed up and requires re-cal. I have
attempted re-cal, and went from a "Test 04 Failed 04" to a "Test 04 failed
02" which is a limit failure. Channel 2 "calibrates" up to the 10V input
(cal 02), and I get a Limit 130 error, no matter what I try, so I assume
that is my problem. In the non-calibrate run mode, the channel 2 input only
works up to the 500 mV range (Hi-Impedance input with co-ax) and with the
10X probe, up to 5V. The display range readout works, but in the 1V, 2V and
5V ranges, it appears to stay in the 100 mV, 200 mV and 500 mV ranges, so it
appears the attenuator isn't switching properly.

Is there a way to tell whether it is the attenuator, or if the proper
outputs are not getting to the drivers for the attenuator relays, or is this
still a calibration problem? I have no way to monitor a "word" from the
processor at this point. I did try monitoring channel 1 at the drivers and
comparing them to channel 2, but found it difficult to get any meaningful
data. Any help will be appreciated.
GerryR

Siggi
 

To diagnose the attenuator relays you can simply measure the DC resistance
while you run up and down the scale. It should be 1MOhm within fairly close
tolerance throughout. If you have bad contacts you'll see non-trivial
deviations from that.

On Thu, Oct 17, 2019 at 12:18 PM machineguy59 via Groups.Io <machineguy59=
yahoo.com@groups.io> wrote:

You should be able to hear the relays switch as you change scales. That
will indicate the logic is operating. It is more likely the attenuator is
dirty and the fingers don't make good contact on the ceramic substrate.
Cleaning is a delicate process to not break the ceramic or bend the contact
fingers. Sometimes you can clear the problem by spraying a contact cleaner
into the attenuator. But the best, long term solution is to open the
attenuator and clean it, OR replace the attenuator. Both are involved
processes.
On Wednesday, October 16, 2019, 06:58:23 PM CDT, GerryR <
totalautomation1@...> wrote:

That's the problem, in the normal mode, the 1, 2 and 5 volt ranges are
all
off, for example, a 1V signal on the 1V per division scale, displays as if
on the 100 mV scale, etc., so I am assuming the attenuator is not
switching
for those ranges, but don't know if the relays in the attenuator, or the
logic telling which tells them to switch that is bad. The digital readout
shows 1V on the 1V scale but the display of the wave is as if it is on the
100 mV scale.
Is there a list of digital words for the different scales or a way to tell
if the logic is bad?

GerryR


----- Original Message -----
From: "machineguy59 via Groups.Io" <machineguy59=yahoo.com@groups.io>
To: <TekScopes@groups.io>
Sent: Wednesday, October 16, 2019 6:48 PM
Subject: Re: [TekScopes] 2465A channel 2 problems


How does Channel 2 work when using the scope in the "normal" mode? If it
seems about right (just not precisely calibrated) when measuring known
voltages then the attenuator is switching.
On Wednesday, October 16, 2019, 03:31:47 PM CDT, GerryR
<totalautomation1@...> wrote:

A little history first: Acquired the 'scope recently and everything was
working fine. Old battery dated 07-87. Decided to change battery and took
all known precautions, but somehow screwed up and requires re-cal. I have
attempted re-cal, and went from a "Test 04 Failed 04" to a "Test 04 failed
02" which is a limit failure. Channel 2 "calibrates" up to the 10V input
(cal 02), and I get a Limit 130 error, no matter what I try, so I assume
that is my problem. In the non-calibrate run mode, the channel 2 input
only
works up to the 500 mV range (Hi-Impedance input with co-ax) and with the
10X probe, up to 5V. The display range readout works, but in the 1V, 2V
and
5V ranges, it appears to stay in the 100 mV, 200 mV and 500 mV ranges, so
it
appears the attenuator isn't switching properly.

Is there a way to tell whether it is the attenuator, or if the proper
outputs are not getting to the drivers for the attenuator relays, or is
this
still a calibration problem? I have no way to monitor a "word" from the
processor at this point. I did try monitoring channel 1 at the drivers and
comparing them to channel 2, but found it difficult to get any meaningful
data. Any help will be appreciated.
GerryR











GerryR
 

Chuck,
Are you saying that the scope CH 1 & 2 inputs will be in 50 ohm mode for all the Cal procedures? I did check the inputs in normal mode when switched to 50 ohms, and they are both OK, right at 50 ohms.. I haven't checked their state when in the different Cal procedures; I'll be back at it a little later.

Also, I don't hear CH 2 relays clicking when going from the 500 mV to the 1 V scale; OK from 50 mV to 100 mV. The inputs stay at 1 M throughout the ranges for both CH 1 and CH 2, but I expect that particular relay isn't being activated for CH 2, so it is stuck in the 500 mV range and showing a "good" 1 M input.

I'll have to look at the schematic and see if I can jumper the proper relay to activate the 1 V scale change. They are OC Darlington's, so that may tell me whether it is the attenuator module relays or if the software or the drivers are the problem. Any other suggestions are welcome!
Thanks.

Gerry

----- Original Message -----
From: "Chuck Harris" <cfharris@...>
To: <TekScopes@groups.io>
Sent: Thursday, October 17, 2019 8:56 AM
Subject: Re: [TekScopes] 2465A channel 2 problems


Hi Gerry,

First, you are not supposed to get a trace, just a pair
of dots, approximately 10 divisions apart.

This is a crucial step, as it affects all future steps.

I would suggest that you always put it in VAR mode, as it
will always give you an adjustable range to hit the mark.

But note: It is most important that the VAR knob be back
in its click before you start the next, and all subsequent,
steps. If you do not do this, you will achieve out-of-range.

If you repeat this step after having done it recently, you
will usually find that the dots are perfectly spaced.

There is no linkage between the 50 ohm annunciator light and
the 50 ohm relay in the preamp. Unless your preamp is broken,
it is in 50 ohm mode.

As a test, when the scope is in normal mode, put the preamps
in 50 ohm mode, and measure them with an ohmmeter. If they
are other than 50 ohm, you have the ever popular burned out
50 ohm load. Unless you are very clever you will be replacing
your preamp, as the resistor is printed on the ceramic substrate.

-Chuck Harris

GerryR wrote:
Another question or two for those in the know: At the beginning of the Cal 02 procedure, it states to connect a 0.5 V standard-amplitude signal to CH 1 and to use CH 2 Position to vertically position the "trace" to within 1 division of the center graticule line, and then to use the CH 1 Position and Volts/DIV VAR controls to obtain a 10-division horizontal signal. I don't get a "trace," only 2 dots. I can position the dots with the controls to put one dot on the first graticule line and the other on the 10th.
Question 1: "Is this "normal," or am I doing something wrong?" I've read and re-read the procedures and can't find any references to this.

Also, at the beginning of the Cal 01 procedure, it states that, "Upon entering Cal 01, the Input Coupling is automatically set to 50 ohm DC ....." This doesn't appear to be true for the other Cal procedures (2,3,4,etc), as I had to install a terminator on my generator to get the actual levels called out in the test procedures (monitored on another scope).
Question 2: "Is this correct, or am I missing something here, as well?

Thanks in advance for any input!

Gerry

Chuck Harris
 

When calibration is under computer control, the computer
will automagically set all of the pertinent controls to their
proper settings for you. If the inputs need to be 50 ohms,
they will be set to 50 ohms.

Just like the manual says.

If your preamp attenuators are broken, they won't do what
they are told to do, and calibration will fail.

Two quick ways to kill the attenuators are to give
them a spray with contact cleaner, or to wash them with
water. The manual warns you not to do either. Somehow
everyone knows better than the engineers that designed
this stuff.

The relays are not made to be water resistant, and will rust
solid if you wash them, and their plastic structure is not
guaranteed to be compatible with anything but isopropyl alcohol.

The relays are a latching variety that was devised and made by
tektronix. They are set or reset by giving the appropriate coil
a little pulse of current. They are not strong enough to release
if there is oil (contact cleaner) between the armature and the
pole piece. The surface tension will for all intents and purposes
glue them into one position.

-Chuck Harris

GerryR wrote:

Chuck,
Are you saying that the scope CH 1 & 2 inputs will be in 50 ohm mode for all
the Cal procedures? I did check the inputs in normal mode when switched to 50 ohms,
and they are both OK, right at 50 ohms.. I haven't checked their state when in the
different Cal procedures; I'll be back at it a little later.

Also, I don't hear CH 2 relays clicking when going from the 500 mV to the 1 V
scale; OK from 50 mV to 100 mV. The inputs stay at 1 M throughout the ranges for
both CH 1 and CH 2, but I expect that particular relay isn't being activated for CH
2, so it is stuck in the 500 mV range and showing a "good" 1 M input.

I'll have to look at the schematic and see if I can jumper the proper relay to
activate the 1 V scale change. They are OC Darlington's, so that may tell me whether
it is the attenuator module relays or if the software or the drivers are the
problem. Any other suggestions are welcome!
Thanks.

Gerry

 

Chuck Harris wrote:
"Two quick ways to kill the attenuators are to give
them a spray with contact cleaner, or to wash them with
water.  The manual warns you not to do either."
I stand corrected and educated.  Thanks, Chuck, I missed that in the manual.  

GerryR wrote:

Chuck,
        Are you saying that the scope CH 1 & 2 inputs will be in 50 ohm mode for all
the Cal procedures?  I did check the inputs in normal mode when switched to 50 ohms,
and they are both OK, right at 50 ohms..  I haven't checked their state when in the
different Cal procedures; I'll be back at it a little later.

        Also, I don't hear CH 2 relays clicking when going from the 500 mV to the 1 V
scale; OK from 50 mV to 100 mV.  The inputs stay at 1 M throughout the ranges for
both CH 1 and CH 2, but I expect that particular relay isn't being activated for CH
2, so it is stuck in the 500 mV range and showing a "good" 1 M input.

        I'll have to look at the schematic and see if I can jumper the proper relay to
activate the 1 V scale change.  They are OC Darlington's, so that may tell me whether
it is the attenuator module relays or if the software or the drivers are the
problem.  Any other suggestions are welcome!
Thanks.

Gerry