Datron/Wavetek 1271

[jfphp]

Hello,

I have just got a Datron Wavetek 1271 with options 10 (AC) 20 (Ohms) and 30 (current). At power up it displays
9005,9  pon    tru/compl     001736
According to the manual 9005 is a serial interface error bur nothing about 9 and the pon... Before desoldering all the IC involved does anybody have an idea for identifying the failed part of the serial interface ?
Thank you.

[ebclr]

The default suspect for instruments old like this one are

Connectors

Capacitors

Clean up all connector, take a visual on all capacitors

[ManateeMafia]

ebclr is correct.

I have a 1281 that had a 9005 error. One of the ribbon cables was disconnected to one of the option boards.

Changing the capacitors fixed other issues with failing self-tests so keep them in mind. They all looked good visually.

[pelule]

nothing to add to the already good expertise of above posts.
Just a tip to the great 1281 repair report of Todd Micaleff:
https://xdevs.com/fix/d1281/

[jfphp]

Thank you but I have not posted the thread in the beginners section. I have found the very interesting xdevs 1281 repair description (thank you Google) and, of course,
I have changed all the caps
I have checked inguard and outguard power supplies, DC and AC ripple
I have checked the various connectors and the various flex cables (long and tedious !).
Therefore my precise question...

[pelule]

Thank you but I have not posted the thread in the beginners section.

Noted, and I apologize for that link - It wasn't my intention to classify you experiance.
I just have thought, Todd my a good help - even an expert may overlook something.
Ups, why I apologize for offering my help free of charge. 
If there is no interest in my ideas/tipps - I have enough paid work to do.

[ManateeMafia]

You could have mentioned changing the caps and checking the cables... I think the response from everyone would have been a little different.

The next step would be, for me, testing the optoisolators. I have attached a copy from one of the pages in the service manual for the 1281. There is a description of the serial path used to talk to the options boards.
I would also think about disconnecting all the boards, one at a time,  and jumpering the links shown in the attached file. I haven't tried this myself but I think this would bypass each board and narrow down the cause of the error.

[jfphp]

Brilliant idea ! I had noticed the jumper along each of the 3 ribbon connectors going to the option boards underneath but I had not made the intellectual link with the serial...link of the instrument. The AC board is faulty : with its jumper bypassing it,  the 1271 is fully functional, of course without AC option. I know now what I have to do... Thank you very much.

[ManateeMafia]

I am glad it worked for you. Any further t/s on the AC board would be welcome info.

[jfphp]

One of the serial TX/RX CLA3106 (M401 for the 1271 -- M801 for the 1281), mounted by chance on a socket, was defective. The voltmeter is now apparently OK but when I launch a self test I get "Require int srce cal 2105" and when I try the internal source cal I get an error "Fail DCV 2192", error for the zero of the 100V range, like the error encoutered on the Xdevs for the first 1281 repaired. Unfortunately there is no indication how this fault was cleared ( explained for the second repair but for an AC similar fault). Just a  question : how was the real faulty offset mesured ?

[ManateeMafia]

The only components changed on the DC assembly were the capacitors. I did replace the 100uF 25V caps near the front of the DC assy on one meter but not the other. They are the ones where one leg has insulation on it. It did not appear to make any difference so I did not replace them on the second meter. That information was not added to the article so it will have to be updated. Also, the front input flexible input cable was not connected properly and you can see from the pics the screw was missing. I think I already reseated the cable by the time the photo was taken.

Of note, a full cal has not been performed on them as I was waiting to get access to better gear. I plan on doing them in the next few weeks since I have had some of my test equipment calibrated recently.

The failing test looks like it is a zeroed input on the 100V range. What kind of values are you seeing if you short the inputs and select 100VDC? It should be between -1mV and +1mV.

[jfphp]

If I short the 100V input, I get about 850µV (Under 1 mV) but the path 021 gives 16 µV (above the limit 10µV) and I get error 2192. Little schocks on two relays  involved in the gain of the preamplifier modify heavily the 16µV  : it is going down or up.... These relays don't exist in the 1281 where the dc assy has nothing to do with the 1271... I will change the two relays S2-L-6V but they are very difficult to find and the only seller in Germany has a  prohibitive price (the 1281 has 2 relays S2-L-6V and the 1271 5 !!!)
Moreover I have started to sweep all the documented paths in the instrument and, almost at the starting point "Ref ratio test",  I get overload for the paths P004 and P005 +Ref comp and -Ref comp. Could you please mesure the TP403 and TP404 on your 1281 (the test point numbers are not the same for the 1271...) with reference to ground 13 (Schematic diag "References and signal switching", sheet 4 of 9 devoted to DC assy).
Than you