Vintage Teardown: RFT G-1004.501 (DMM)

[kblue]

Vintage Teardown: RFT G-1004.501 (DMM)

Part Nr. 1 - The outsides!

Greetings!

Mayhaps stuff like this is kinda interesting for some folks. Its a simple one but i do like this old stuff and tech

This particular unit was sold on: 25. October 1990
3 1/2 Counts
DC V ranges: 200 mV, 2 V, 20 V, 200 V (0,25% +2) // 1000 V (0,5% + 2)
DC A ranges: 200 mA, 2 mA, 20 mA, 200 mA, 1000 mA (0,5% +2) // 10 A (1% +2)
AC V ranges: same as DC (1% +4 for all ranges)
AC A ranges: same as DC (1,25% + 4 for all ranges)
Ohms: 200, 2k, 20k, 200k, 2000k, 20M (0,5% +3)
Diodetest: 0,1 mA / 0 - 1,999 V (max. out: 3,4 V) + Continuity
Batterylife: >1500 h

This meter seems to be working just fine, except for the black zones within the LCD. So far it seems to be within spec! So nothing to repair i guess For the first post, i'll show some pictures from the outside, the battery compartment and the schematics. There will be more from the inside later this week.



With the original box, documents in rus + ger language, schematics and a warranty card its quite a good catch!



The display (9mm in heigh) has its problems. But its usable! I could remove the polarization filter But as some of you know, it wouldn't be usable from that point forward.



The original schematics. In this case the RUS variant. The other one would be in german.



The bottom side with some markings like "RFT veb mikroelektronik >karl marx< erfurt" (RFT = Rundfunk- und Fernmelde-Technik / veb = Volkseigener Betrieb [publicly owned enterprise) and yes, this meter needs 6 batteries! And no, your eyes don't deceive you ... i use miserable Vartas. I had these on hand. I'm sorry! Please put the stones back to the ground where they belong and don't use them as a throwing weapon!

[kblue]

Part Nr. 2 - The inside!

But wait, there is more!



Ye, switches are big and they take a lot of space.




Big solderjoints for the 10 A Shunt. Guess something like that wouldnt pass safety ratings today?



1kV Input Section with a big resistor. Speaking of Resistors ...




This meter is packed with resistor-networks. Some might be even precision work (-: What else do we need in such a nice meter? Mhmm.



Chunky diodes of course! Who does not want some chunky diodes in his / her meter? It seems these diodes or rather the legs are cursed with tin whiskers?



One of two main attractions! The Chip C7136D, which seems to be a copy of the ICL7136 (Data Sheet from analog.com).



The second main attraction! Our 1,235 V Vref B589Nm (50 ppm/C°) which is a copy of the AD589. No surprise at all, eh? So far the meter seems stable and accurate for its 2000 Counts. The display is a bummer, mayhaps i'll source another unit with missing parts or something for a display-swap.

Best wishes!

[coromonadalix]

must be a rebranded intersil 7106 lcd  dmm