Thanks for quick replies! I'll try answer one by one without an order.
- Actually, though I asked general advise, not tied to particular equipment, there were some issues with my r6871e dmm, thats why I ask about film caps: after cleaning, and before I did any soldering (with except of AC power transformer voltage configuration), I tested some functions, and got a lot of offsets in any func/range:
200mV DC: +16,5uV, 2VDC: +21,4uV, 20VDC: +72uV,
10 Ohm: -0,17894, 100 Ohm: -0,17885, 1k: -0,1789,
2mADC: +44nA, 20mADC: +0,34uA…
Though nulling it and measuring against ad7461a gave pretty accurate values, so I thought may be problem with film caps in input circuits to filtering (ofc I do not want to touch integrator cap, wich may affect factory calibrated linearity). Also those values almost not changed after recap and further cleaning.
- About switching reg, ofc I won't place it in analog board (analog and digital are different board), but just for digital with a lot 74ls and other old thick process IC, I think it would be nice to not add more heat to prolong it's life. Also continious conduction buck converter introduce no wideband noise.
- Yes, I used canned gas for cleaning.
- As for metrology, it come in pretty dusty condition, but with traces of extencive use in past, also with no cal labels. Besides
my precious r6871e, I have ad7461a, a pretty modern 6 ½ DMM with usb, with expired cal half year ago, and r6144 voltage-current generator in excelent condition (checked with ad7461a). I planned to cal ad7461a, but seems cal lab in my city can't handle 6 ½ class dmm, so I leave this task for a while.
- I saved both eprom contents after checked some funtions and self-cal procedure work normally, but seems xdevs already have A00 revision dumps
.