Another update on this, long term project and I believe I've found a faulty relay.
So with A20+A19+A18+A17+A7+A8+A9+A10+A11 cards installed, running the self diagnostics revealed no faults (besides the usual complaints about missing cards) However I still seemed to have a problem with my DC voltages tens of thousands of % out of spec and drifiting. Trying to nail the culprit here is tricky. Even trying to identify the faulty card was hard. So I added in the A12 card so that I could learn a bit more and see if I could identify any functions not working at all that may help.
Well as soon as I added the A12 card then I got 4 A8 relay faults flag up. SO what has changed here. Well the A12 card adds some ACV functions, 2.2v and 22v. A8 then divides these down to make 2.2mV, 22mV, and 220mV ranges.
Going through the troubleshooting revealed no problems until the last step
"Check the mV Dividers. Set the 5700A to 200 mV at 1 kHz, operate. Using a DMM
measure the ac voltage at the cathode of CR6"
Setting the calibrator to 200mV 1khz caused it to trip out to standby mode. In fact, setting any of the AC mV ranges caused it to trip out. 2.2v and 22v worked ok. So there is a problem here!
I investigated the divider circuits, and used the tables in the A8 schematic to trace through the relay paths. And I found the A8 relay K15 is stuck in the "SET" position. this should be in the "RESET" position for all the AC mV ranges. It could still be a faulty driver IC, so I removed the A8 card and manually applied 5v to the K15 relay reset coil... nothing, nada, no click. So it appears I have a faulty relay, probably the contacts have stuck in the "SET" position.
This is bad because K15 and K33 both connect to the out/sense low line, but not at the same time. With this fault it allows both relays to connect to out/sense low at the same time. Maybe this is contributing to the DCV volt problems, maybe not, but it certainly looks like a faulty relay here and it needs replacing.
Two questions
1. Whats the best way to remove the relay without damaging the pcb ? I don't think solder wick is going to work here. A hot air gun may work... or it could just lift the pads. I'm aware this is through plated and theres a risk of pulling pads from the opposite side of the board.
2. where is a good source of replacement relays ? they are obsolete and out of stock now from most mainstream suppliers. There are quite a few sellers on ebay, but there's always a risk of buying fake or factory reject parts.