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HP 973A & 974A Multimeter Service Manual anyone?

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kipp:
Regarding the higher precision versions, the Yokogawa model numbers are 7544-01 and 7544-02, but it's hard to find documentation for them.

AMR Labs:

--- Quote from: kipp on October 08, 2020, 03:52:58 am ---Regarding the higher precision versions, the Yokogawa model numbers are 7544-01 and 7544-02, but it's hard to find documentation for them.

--- End quote ---

Mentioned and pictured earlier in this thread:
https://www.eevblog.com/forum/testgear/hp-973a-974a-multimeter-service-manual-anyone/msg2690670/#msg2690670

Pisami:
I found the 20 kHz model from trash and it was labeled as broken. I regularly fix interesting electronics as a hobby and I grabbed it. Sure, it had green-blue death from leaked batteries and it required a lot of elbow grease to get most of it away. Glad to see that others have also succeeded. The battery connects are a bit flakey still and the Power button does not want to co-operate. I'll need to check the above posted fix if it helps, but I have already tested that everything works when covers open and the DMM is powered on from board directly.

Nobody mentioned that there are 4 pinholes on the very top of the PCB. I soldered pin headers to them in hopes they are non-documented serial output, but I haven't had the time to measure what they do. Any ideas?

AMR Labs:
Unsolder the battery contacts and use vinegar to get the blue-green corrosion off, then wash off with water and leave to dry before reinstalling. Repeat as necessary until all corrosion is gone. Also make sure both PCBs are clean as any slight deposit from the battery acid fumes can create problems. Also make sure no tracks have been damaged by corrosion. There are a few very fine tracks near the battery holder that I had to repair as they had been eaten away by the acid.

No idea about the 4 connections you mention, but please let us know what you find out.

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