[Zelandeth]

I have a sneaking feeling given that we've got a reference voltage either missing or way out of whack given the symptoms we've got...

Voltage readings are all over the shop (they do respond to input, but not correctly and not consistently).
Vacuum reading never settles to zero, and wanders.
Temperature probe is reading nonsense, apparently offset + about 150C.
No valid calibration reported from the gas analyser.
Current clamp reading nonsense.
Ohmmeter giving no reading, no voltage present on the test leads.

The screenshot below was taken with the voltage probes shorted together and everything else just sitting next to the machine.

Just strikes me that all of these could well be impacted by a fault of this type...so I think the sequence of events needs to be to get the voltmeter sorted first I think. Wouldn't surprise me at all if once that was up and running it a lot of other instruments followed suit.

Given the tiny signals that the photodiodes in the gas analyser (assuming that's what the detectors are, rather than pyroelectric sensors...have to confess slight ignorance on that bit) are I think expecting that to play ball when we've got potential power supply or reference voltage issues is vastly optimistic. It was filthy throughout on receipt, but has been (very carefully!) cleaned now. One thing which does seem odd is that the detector is pushed right over to one side of its mounting slot...though there's no witness marks to suggest that this has happened recently, so it may well have been set up like that originally. I'm not about to go messing with the alignment unless I'm given an actual reason to. Oh...and I'll need an imperial set of Allen keys for that anyway as those as with every fastener on the machine are imperial because it's American.

I'll pull all the boards again tomorrow if I get a spare half hour and do a head-count to find out how many Tantalum caps I've got to replace...Figure I may as well just do the lot as one job as it won't really take long and at least then I know it's done and something I can tick off the potential gremlin list.