Vintage Teardown and hopefully repair: RFT G-1001.500 Benchmultimeter

[hli]

It says Common Anode there...

The site says that, but the data sheet clearly shows the common cathodes (K1 and K2). I think I have four at home (in an ADC setup which might quite as old as this meter...). So when I'm back home at the weekend, I will try to look at them more closely.

[Thilo78]

The site says that, but the data sheet clearly shows the common cathodes (K1 and K2).

No, I fell for that one at first, as well.
K1 and K2 are described as Anodes underneath the sectional view.
A..H are the Cathodes as per the pic.
That I could confirm by measurement on the units in the G-1001.500 and the VQB71 I have as spares.

I think I have four at home (in an ADC setup which might quite as old as this meter...). So when I'm back home at the weekend, I will try to look at them more closely.

That sounds great. Let me know the result 

[hli]

Btw: as far as I can tell from the images, there are no russian ICs or packages in there. Everything seems to be made in the former GDR, with some parts from Tesla in Czechoslovakia (like the MAA725). The A109 is the east german version of the uA709. All the ICs named D1xx are 74xx parts, following the same naming schema.

For most of the discrete components, use this cross-reference: http://www-user.tu-chemnitz.de/~heha/bastelecke/Konsumg%C3%BCter-Bastelei/DDR-Halbleiter/ to find out what the equivalent is. For smaller transistors, the first letter is missing on the package (so the transistors on #53 are SC239E). The diodes sometimes have just a color code on their top. The date code is typically just a letter-number combination (in #53 looks like a K8 or K9). Zener diodes have the voltage on them, and the date code below.

Also, the company where schwarz-brots unit comes from was manufacturing industrial ceramic stuff, including resistors (see http://www.robotrontechnik.de/html/standorte/kwh.htm ). Some of the resistors in this DMM actually come from there! (as can be seen by the logos on them)

[hli]

K1 and K2 are described as Anodes underneath the sectional view.
A..H are the Cathodes as per the pic.

Oh you're right. Datasheets don't lie, except when they do

[Thilo78]

Oh you're right. Datasheets don't lie, except when they do

 
At least measurements don't lie.

Those I did yesterday confirm the (latest) version I quoted here.
So I wondered about K1/K2 being anodes, but that was okay for me as it's backed with measurements.

[Thilo78]

Any news about the G-1001?

Mine is doing well. I only had to replace one of the 7-segment-displays. (the right-most)