Electronics > Metrology

Datron 1081 Teardown and repair

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MaxFrister:
I recently acquired a Datron 1081.  The Datron 1081 is a 7½ digit meter and is similar to the Datron 1071 but higher specs. 

Basic 24 hour specs:
                   1071                                  1081
10VDC        +/-2ppm +/- 4 digits         +/-2ppm +/- 1 digit
10VAC        +/-0.04% +/- 40 digits      +/-0.01% +/- 0.005%
10k            +/-5ppm +/- 2 digits         +/-3ppm +/- 1 digit

The 1071 was designed about 1975, the 1081 about 1983.   The 1081 achieves its resolution using a network of 4 selected temperature compensated zener diodes.

My unit was advertised as broken and no display.  Unfortunately, for once, the advertisement was right.  Preliminary checks showed the wrong fuse installed.  After installing the right fuse, the -175V rail was missing.  Further checks showed the transformer damaged.  The previous owner apparently used the transformer as a fuse.  There was also serious corrosion on one of the voltage regulators (a common problem, perhaps related to the wrong flux).

I’m waiting for caps and other parts to arrive to do some basic repairs to the power supply before I continue testing.  In the meantime, I thought I’d post a few pics.

Basic machine



The magic, 4 zeners


Corrosion on TO3 package wires



p.s.,
As I mentioned, I’m probably in the market for a new transformer.  If you happen to have a parts machine and you’re willing to part with it send me a pm (I believe that the 1061,1062, 1065, 1071, 1072, 1081 and 1082 all use the same transformers).

maginnovision:
I've got 4 datrons and none of them have issues with the 5V reg or wiring, seems like I got lucky. After a bit of cleaning it'll look nice, really sad about the transformer though. I saw that in another unit and passed on it for that alone.

Johnny10:
Are you in US?

branadic:
Missing display? I'm working on a replacement solution.
https://www.eevblog.com/forum/repair/datron-4000a-getting-at-test-points/msg2295153/#msg2295153

-branadic-

DC1MC:
That's not looking like a damaged display (except the broken ones with compromised vacuum, all Datron displays turn on a bit if powered correctly), it looks like a display without power !!!

After you're done with restoring the powers supply fully and getting rid of the 169% dead elcos you may have a nice surprise  ^-^.

 Cheers,
 DC1MC

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