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BBC Goerz Metrawatt MA 4E Service Manual and calibration

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ErnestB:
Would anybody here have some information on how to calibrate and/or have schematics of analogue multimeter BBC Goerz Metrawatt MA 4E (besides the German user manual)? T.i.a. 

ErnestB:
Edit: Calibration done, but service manual incl. schematics would be a nice to have.

ErnestB:
Edit 2: The meter works great EXCEPT on the resistor measurements. On the range kOhm x 1 and kOhm x 10 the meter does not go to "infinity" with open leads, but rather shows about 100k. I have a theory that the battery acid come into the meter and have influenced the PCB and created this parallel "resistance". I have bought this meter on our national second hand "ebay" (called Marktplaats). The seller had some photo's where I could see some white tarnish (the battery compartment is clear plastic). So the seller cleaned it up at made some new photo's and said "I sell the meter with clean battery compartment, as you can see". Well I think the seller is kind of honest, as he was convinced that the meter is just good, and didn't realize that that battery leakage has done anything. As the battery compartment is not directly within the electronics and the defect was not obvious. Anyway, I knew almost for 100% sure that the battery leaked once, but was hoping that it doesn't influence the meter. I do not have any evidence that my story adds up, but I think it makes sense. As said I could calibrate the meter for DC and AC voltages. I could sneak a peak inside and could see that one of the battery contacts was partly "eaten" with a small hole in it. It could be difficult task to find those 100k somewhere in the PCB I suppose, and to eliminate that maybe even impossible...

ErnestB:
This problem is quite typical one. Battery left in the equipment that destroy the equipment. I had this CASIO fx-82SX for years and years. Problem of the calculator is that it uses only 400uW of power, and that battery at the time for replacement already leaked it's toxic blood, that it destroys the calculator. So when I have noticed that the digits have less contrast I opened it up and could see that the battery had leaked. I cleaned it up and put a new battery, but damage was done. The acid already crawl under the display contacts and yeah, not good  ;D

ErnestB:
Update: Found the schematics at radiomuseum.org, AFTER I have repaired the multimeter  ;D
The whole time I was on a trail that the acid from a leaked battery caused the extra lower unwanted input resistance of about 100k.
But at one point I found a small capacitor of 220p to be causing the trouble (the function I was not sure of until I found the schematics).
Replaced it with 47p as that value was working the best, and that value is suggested on the IC datasheet... Anyway, happy I could repair it to it's full functionality.

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