Continued: 2465B CTT/HPIB/WR TEST 05 fail 42, all CTT fail


Jean-Paul
 

Hello again: The continuing saga ... (see my pervious posts re CTT and vet nonlin)

1/ New U400 channel switch 155-0236-00 has fixed the CH1, 2 nonlinearity.
2/ Chuck mentioned that the CTT test fails and TEST 05 FAIL 42 may be due to the U500 trigger hybrid 155-0239-xx, that some may work otherwise but fail in a CTT scope.
I have two spares off epay, but exchanging for the original U500 gave no change. Perhaps the epay units also have the same fault?
3/ Today I tested my working 2465B CTT and 2467B CTT and both pass all tests and accurately measure the 10.000 output of a Leo Bodnar GPS.
I have now exchanged the working units U500 trigger hybrids into the fault unit, but again no change, all faults still present.
4/ The option board has an EEPROM, could that be the culprit? I have also exchanged it with a working unit and same result.

IF I remove the options board and place the 4 jumpers on A1 board, the self-tests without any options pass fine.

Any ideas for next steps are appreciated.

All the Best,

Jon


Chuck Harris <cfharris@...>
 

I think I am missing something:

Did you try swapping the CTT from the scope with the error message
into the scope that has a good CTT board?

Did you try swapping the good CTT board into the scope with the
error message?

-Chuck Harris

Jean-Paul wrote:

Hello again: The continuing saga ... (see my pervious posts re CTT and vet nonlin)

1/ New U400 channel switch 155-0236-00 has fixed the CH1, 2 nonlinearity.
2/ Chuck mentioned that the CTT test fails and TEST 05 FAIL 42 may be due to the U500 trigger hybrid 155-0239-xx, that some may work otherwise but fail in a CTT scope.
I have two spares off epay, but exchanging for the original U500 gave no change. Perhaps the epay units also have the same fault?
3/ Today I tested my working 2465B CTT and 2467B CTT and both pass all tests and accurately measure the 10.000 output of a Leo Bodnar GPS.
I have now exchanged the working units U500 trigger hybrids into the fault unit, but again no change, all faults still present.
4/ The option board has an EEPROM, could that be the culprit? I have also exchanged it with a working unit and same result.

IF I remove the options board and place the 4 jumpers on A1 board, the self-tests without any options pass fine.

Any ideas for next steps are appreciated.

All the Best,

Jon










Jean-Paul
 

Dear Chuck:

I swapped only the U5930 of the OPT boards, as it was easy and socketed, the EEPROM. No change.

I am just now removing and exchanging the OPT bd of known good unit to fault unit.

Will report soon!

Jon


Jean-Paul
 

Chuck, with known good CTT board exchanged for the one in the failed scope, all cables properly reattached.

A5 board is know good and had no SMD leaky caps.

Only, partial success, CTT works but the following faults on self test:

Test 01 -06 PASS

CT TEST 81 Fail 03
CT Test 86 Fail 02
All others PASS

So really confusing results.

Your thoughts?

Jon


 

On Tue, Feb 23, 2021 at 09:16 PM, Jean-Paul wrote:


Only, partial success, CTT works but the following faults on self test:

Test 01 -06 PASS

CT TEST 81 Fail 03
CT Test 86 Fail 02
All others PASS

So really confusing results.

Your thoughts?
The 81 errors are related to CTT (non-)calibration. Not unexpected, since you replaced the option board. This was discussed a while ago in this group.
The 86 error quite likely is linked to the same.

Raymond


Chuck Harris <cfharris@...>
 

The Test81, Fail 03 is a combination of a Fail 02, and Fail 01,
which means that your reference oscillator is not calibrated.

The Test82, Fail 02 is hopefully spurious. Everything is closely
dependent on the oscillator being right. Let's just say that I have
seen it spuriously appear when the reference is uncalibrated, and
spuriously disappear after calibration.

Calibrating the CTT is easy, if you have a good clean frequency
standard that can make either a 50% duty cycle 1Vp-p square wave,
or a 1Vp-p low distortion sine wave at the correct frequency and
stability.

I use an HP3336B, with my GPS disciplined Rb lab standard as
the reference. The 3336B with the high stability option would
be fine by itself.

The HP is set to 1MHz, and makes a nice low distortion sine wave
referenced to the lab standard or internal reference.

-Chuck Harris

Jean-Paul wrote:

Chuck, with known good CTT board exchanged for the one in the failed scope, all cables properly reattached.

A5 board is know good and had no SMD leaky caps.

Only, partial success, CTT works but the following faults on self test:

Test 01 -06 PASS

CT TEST 81 Fail 03
CT Test 86 Fail 02
All others PASS

So really confusing results.

Your thoughts?

Jon







Jean-Paul
 

Chuck many thanks thought so,

Yes I have gone thru Calibrating CTT proceedure and aware of the specific requirements for the signal.

Have all the stuff needed to do it.

As I have mounted a subsitute A5 bd need to replace to the original and do a full CAL anyway.

However it means that the original OPT board has an issue that caused the other flaky tests as orig OPT bod ALL CTT tests fail.

Real puzzle,

Enjoy,


Jon


Chuck Harris <cfharris@...>
 

Hi Jon,

Well, that is what the board swapping was supposed to
determine. Now your efforts can be focused on just the
CTT board.

-Chuck Harris

Jean-Paul wrote:

Chuck many thanks thought so,

Yes I have gone thru Calibrating CTT proceedure and aware of the specific requirements for the signal.

Have all the stuff needed to do it.

As I have mounted a subsitute A5 bd need to replace to the original and do a full CAL anyway.

However it means that the original OPT board has an issue that caused the other flaky tests as orig OPT bod ALL CTT tests fail.

Real puzzle,

Enjoy,


Jon






Jean-Paul
 

Dear Chuck

The CTT option operation and self test seems to be dependent upon

1/ CTT board, EEPROM on board
2/ Trigger Hybrid U500, only certain ones work, even though they may work fine in a non CTT scope.
3/ successful CTT calibration, stored on NVRAM of A5

At the moment I have all three of these factors in question, as the original A5 board is in the hands of a friend to do the SMD leaky cap clean-up and NVRAM replacement. So, I am using another scopes A5.
I shall get the original A5 back and see if that changes anything after a CAL attempt.

The design of the CTT option seems rather flaky, to depend on unspecified U500 properties.

Kind Regards

Jon


Chuck Harris <cfharris@...>
 

Hi Jon,

I guess, but how would you get the zero crossing/trigger
points into the CTT?

Tek used a combination of features in the trigger hybrid,
and a PAL that they grafted onto the trigger hybrid to
massage the signal from the vertical trigger tapoff so that
the CTT could time it... all a reasonable thing to do.

I have some suspicion that the unfortunate problem with
the trigger hybrid when doing CTT functions is the interface
between the PAL and the trigger hybrid. Perhaps the PAL's
inputs are too heavy of a load for some trigger hybrid's
outputs?

Or maybe there is a timing issue between the PAL and the
hybrid?

It could even be something as stupid as a failed internal
pull up resistor on one of the hybrid's input/output pins.

Some simple probing around on the PAL may be in order.

I have never found the PAL, or the PAL's socket to be the
problem, but I have found trigger hybrid swaps will make
things happy.

-Chuck Harris

Jean-Paul wrote:

Dear Chuck

The CTT option operation and self test seems to be dependent upon

1/ CTT board, EEPROM on board
2/ Trigger Hybrid U500, only certain ones work, even though they may work fine in a non CTT scope.
3/ successful CTT calibration, stored on NVRAM of A5

At the moment I have all three of these factors in question, as the original A5 board is in the hands of a friend to do the SMD leaky cap clean-up and NVRAM replacement. So, I am using another scopes A5.
I shall get the original A5 back and see if that changes anything after a CAL attempt.

The design of the CTT option seems rather flaky, to depend on unspecified U500 properties.

Kind Regards

Jon