Electronics > Metrology

Datron Wavetek 1271 1281 self test question + details of successful repair

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doktor pyta:
Is there some magic way of performing self test step by step ?
This would be useful during troubleshooting.

ManateeMafia:
There are many Pathway commands that can be accessed from the front menu. This gives you real time data while troubleshooting.

There is mention of it in the 1281 service manual Section 2. I think the Pathway codes start with a P (ie P007)

doktor pyta:
I missed that. Thanks!!!

doktor pyta:
Cut from EEVBlog Repair section:

'I was a happy user of 1271 until yesterday.
When I bought it I replaced internal battery. Everything was fine.
It was passing full and fast self test without problems.

After 3 days of constant work I noticed that AC measurement was not correct.
What is more, the 100mV and 1V ACV ranges showed ERROR OL even with input terminals shorted.
Also ACI on all ranges showed ERROR OL.
After this self test shows multiple errors related to AC board.

First I thought it is due to electrolytic capacitors, however the voltages and ripple were in reasonable level.
I started tracking the issue. After some time i found a VERY strange defect: shielded reed relay RL104 had shorted shield with the coil's terminal (two other relays don't behave like this). Fortunately I had such relays from old DATRON DMM. After replacing and cleaning all the area the AC measurement is correct again on all ranges. ERROR OL no longer apperars on ACI and ACV. One thing that is strange is that offsets in the AC measurement are significant (0,2V on 1kV range; 1mV on 100mV range).
The self test ends with same errors as before the repair. It doesn't want to perform full self test, because it says it requires internal source calibration. When I run this internal source calibration it finishes with error related to ACV and ACI.

P.S. DCV and RES functions work really good (stability <1ppm/3 days)
P.S.2 I tried to perform AC calibration at 1kHz, I calibrated all ranges as described in the manual however I had no access to 1kV source. It didn't helped.

Does anyone have similar problems?
In what cases the internal NV RAM should be erased ?'

My error codes were: 2342; 2322; 2312; 2422; 2432; 2472; 2492; 2512; 2632; 2622


EDIT: the unit passes self test after repair.

The reason of these errors were sticky relays type S2-24V. I had to replace 3 of them RL101, RL102, RL103.

Bonus: photo of faulty components.

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