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Test Equipment Anonymous (TEA) group therapy thread

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grizewald:
More Datron 1071

As I said in my last post about this meter, there's no such thing as a perfect one when you're talking about something from the mid '70s.
Mine was no exception, and although the meter powered up straight away when I received it and seemed to give plausible results when
reading a few voltage references and precision resistors, it was obvious that the meter wasn't entirely happy. First task was to check the
infamous Philips blue electrolytics.



Sure enough, with one end freed from the PCB, they measured:

Des.        Printed    Actual         ESR
               Value       Value
C45        47μF        34μF           8.1Ω        (Furthest away in the photo)
C46        47μF        34μF           6.4Ω
C47        33μF        28μF           8.1Ω
C48        33μF        25μF           10.2Ω
C49        10μF        9.7μF          4.5Ω
C50        10μF        9.4μF          7.6Ω

The replacements from Kemet and Vishay were a bit of a squeeze, but had rather better parameters:

Des.  New        New
         Value       ESR
C45   50μF       0.22Ω
C46   49.7μF    0.22Ω
C47   32.2μF    1.38Ω
C48   31.5μF    1.44Ω
C49   11.7μF    0.55Ω
C50   11.7μF    0.55Ω



I then checked the various power rails and found out of tolerance voltages and excessive ripple,
so it was time to turn my attention to that area of the meter. This is where the fun starts!

The power supply is implemented on the board that runs across the rear of the meter. Between that and the
rear of the case, Datron also crammed in all of the boards that handle the optional outputs, the front/rear
relays and the two stacked toroid transformers. It's kind of packed in there as you can see from
the photo below.


The only way I could easily work on the power supply was to separate the rear of the case with all its
boards from the rear PCB and remove the analogue, digital and current boards so that I had clear access to the
solder side of the PSU. I wasn't keen on my chances of being able to put it all back together again without
extensive photo documentation of what plug went where - there are no identifying labels on any of the plugs
that connect everything together, so I took my time and took many photos along the way. Finally, the rear
of the case was free!



continues in next post (which will be after I've eaten some strawberries and cream )...

Specmaster:

--- Quote from: bd139 on July 17, 2022, 10:38:08 am ---465 should clean up nicely. Wonder if it works. Plug was cut off everything on the stand



--- End quote ---
Good all the knobs and shafts look to be OK, not bent from being clobbered or dropped, so it should clean up very nicely indeed, looking good so far.

bd139:

--- Quote from: mnementh on July 17, 2022, 03:52:39 pm ---
--- Quote from: bd139 on July 17, 2022, 11:05:29 am ---   ...In other news, frozen pigs just flew out of hell… it looks like it actually works.

Have ID’ed the probe sensor doesn’t work properly on one of the channels but that’s an easy fix. Might even work with a clean.
--- End quote ---

For 20 quid...? Def territory!

mnem
 :clap:

--- End quote ---

Not quite. Full clean and check out…

Issues with channel switching. Looks like dirty switches and possibly a duff probe on my part. Hmm.

mnementh:

--- Quote from: grizewald on July 17, 2022, 10:02:15 am ---Greetings TEA folk!

It's been far too long since I was here last, mainly due to a serious lack of time due to work pressure. As I'm on a nice long vacation from work at the moment, I spent a few days catching up on things here (as best one can for 2000+ pages) and have thoroughly enjoyed myself.

Despite having been pretty much overloaded with work, my GAS problem has continued unabated.


--- End quote ---

Welcome back, BTW... it has been too long.

A while ago I bought this T-shirt for my daughter:   

It reminded me of our conversations about the Koloboks.   :-DD

mnem
*toddles off to shop some spray varnish*

Specmaster:

--- Quote from: bd139 on July 17, 2022, 11:29:40 am ---Put some bananas in before the potatoes too :)

Solartron. Also works apart from two missing decimal points. I swapped a couple of the rather ancient LED displays around expecting that to be the issue but it wasn’t. Hopefully the main IC isn’t at fault  :(

Should read 9.6245.

Got to go do some shopping now  :(

--- End quote ---
If those LEDs are socket based, more than likely to be bad contacts, give it a shot of contact cleaner and a few insertions and extractions to wipe the contacts?

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