I've got a '93 Partner 1 with a strange issue.
When I turn it on, it boots normally to the estop message. I can press reset and clear it, and home the machine.
After somewhere between 2 and 60 seconds later, it goes into an Estop state again, even if I haven't moved anything. If I hold in reset I can operate the machine and it works perfectly otherwise.


I have jumpered across all of the limit switches to rule those or a broken wire out. No change.
Spindle drive is fine, no errors unless the machine triggers the external fault line on estop.
I changed our relays on the mcode board to see if it was a flaky relay. they all seem to work, don't know if the latching circuit for the enable relay could go bad.

I suspected bad capacitors on the 160VDC power supply, replaced those. It stopped blowing the 1A fuse from capacitor - to case gnd, so that's something. No change in Estop behavior though.
It is getting 220.75V 3ph input, so nothing is out of spec there. Shop power is 250V but I ran it through some buck/boost transformers upstream. 110v transformer is outputting 110-111v.

Any idea what else I should check? 24v/15v power supply seems OK but I haven't put an oscilloscope on it yet, so if it's dropping out it's too fast for my multimeter.

I really want to have this running as a second op machine in my shop and not on a truck to the scrapyard, but I am stumped.