More calibrations today. Fluke 8600A. This one did not go well and in fact stopped the process. It's out of spec.
When I first got this 8600A it had severe drift issues. In the process of attempting to repair I replaced the PSU caps, some tants and poly caps on the main board, the 1MHz oscillator crystal, plus a few other parts. I thought the problem was the zener reference itself but it has tested rock stable. I finally tracked the drift down to contact resistance on some of the range reed relays. So I replaced all of them. That finally fixed the drifting issues. I thought all the issues were fixed but apparently not.
I can calibrate the 190mV, 1.9V, 19V, and 190V and they are repeatable and right on. But if I check other DC voltages with the AD584-M the 2.5V, 5.0V, and 7.5V are OK but applying 9.99691V I get this:
10.001V. Way out. Should be max 9.9970V.
![](https://imagizer.imageshack.com/v2/xq90/921/76gbY9.jpg)
So I stopped the cal for now and this guy is in the repair cue. But I think it's going to be a tough issue to track down may not be worth the effort.