So there you are, working on something that you don't have any schematics
for; (in this case a Datron 1281 8.5 digit DMM) This one wouldn't power
up. Poking around I noticed some (TTL) circuits were not getting +5VDC.
Traced it back through a three terminal linear regulator to it's AC input.
Hmmm... Only getting about 5.5VAC, not enough there. Isolate the AC output
from the transformer to make sure it wasn't a loading issue; it's not.
Gets to about 5.8VAC. This unit has two toroid transformers, and the one
I've traced the problem to has 8 wires on the secondary and another 8 on
the primary (sheesh)

I have no idea what the primary voltages should be (As it turns out, about
16VAC. Weird!)

BUT, suddenly I hear a metallic sounding "tick!" and the unit begins
running. (I quickly measure the primaries and note the voltages JIC.)
sounds a bit like a relay, but there's nothing like that in any of the
power supplies (there's a number of them) that I can see. Figuring an
intermittent somewhere I begin jiggling connectors, tapping around with a
screwdriver handle, etc. Nothing. Meter keeps working.

Cold blasts from freeze spray, Heat gun, etc. Nothing.

Turn it off for an hour and back on repeating what I did above. Still
working.

Turn it off for a day and back on. Wash, rinse, repeat. still working
perfectly.

Things like this seem to happen to me often. Is it just me, or do you have
faults like this that drive you nuts?

I don't suppose anyone might have any schematics for this meter, would
they? I think at some point Datron sold off to Wavetek then Fluke ended up
with it, as the user manual is available from Fluke.

Thanks.