I bought a 1960 made Calibration Standards Precision DC Voltmeter DC-100AR in a pile of stuff for $10. I wanted many of the other items and this was a bonus. When I got it, I opened the case and thought it was in pretty good shape except for some caps that leaked everywhere. It is very well made in that most of the systems are modular and made on turret boards. It has a VTVM setting (though it is transistors and not tubes) and then a differential volt meter section. I recapped the unit except for a power supply can cap that holds a 250uf at 6v and a 1000uf at 10v. The meter was broken (pushed in), so I had to work that out a bit to the point it would move. The meter is I was lucky enough to buy a manual. Sadly, the manual's schematic is not complete in that it identifies the parts, but it doesn't always provide the values. The resistors all match the values in the schematic. Some of the caps are written oddly, but I figured that out. The hard part for me to get are the transistors. Most have numbers I have not seen or do not match those in the unit. The 4 transistors in the supply where the encapsulated 6v chopper (copper can) is are labeled 2n213A or have no obvious marking beyond being made by Sylvania and being germanium. The schematic has 4 2N1302 transistors. I cannot find the data on the 2N213A. There are a few other transistors in the unit. None match the schematic 2N406, etc. Any thoughts on whether I should try to find the replacements in the schematic? I have turned it on and tried it, but it is way too sensitive. Also, any idea how to tell the original value of the NTC thermistor if it is not written on it? Any help would be greatly appreciated.
Pictures before work commenced:
I have the exterior case, but forgot to snap a picture.
All socketed construction. You simply pop the circuit from the octal socket and open up each the case to work on the unit.
1 leaked out cap.
3 leaked out caps. Notice that the lead on this one bought it.
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