I just got an old 4020HT with 88HS from -93 installed in the shop and cant make it run.
I seem to have too low voltage from the DC power supply on 5VDC, but -12V and +12V are ok. the max I can get is 5,06VDC after I remove all control cards and remove J9-J13. In this state I can also get 120VAC from the T-816 transformer. Reinstalling the cards I hoped to find the culprit, but it seems like each card is pulling 0,2 - 0,3VDC which means I cant get enough to keep the amp chassi from going into E-stop. Also even though all cards does not blink when installed together, they all blink when installed one at a time, except the A axis. When I try to check for AC ripple I get 10VAC on the 5VDC and 26VAC on the +12VDC. This is quite a lot of ripple, but all my DMM's are really cheap and can not even measure AC current. Only DC current.

Question: Is this a realistic AC ripple? Can it really be that high or is it a bad multimeter?

Since the relays work and let the control 120VAC through if no cards are installed they obviously work. It seems the trick is to get around 5,1VDC while all cards are installed, but how?

The machine used to have a 4th axis installed, but was removed before I got it. the drive card and amp is still in but I can not see any plug on the drive card. I guess I should disable the axis in the control and remove it in case this is causing problems but dont know how?

The Baldor Vector Drive, model INV-0049 has a diagnostic page and says the bus voltage is 345V. the strange thing is that I am only feeding 210V 3 phase to the machine. The log page has 31 identical entires with "DC bus high" so I am starting to wonder. Am I missing something?

As I have no manuals and all the currently available manuals from the Fadal, compuserve etc. web sites are for newer machines with other boards, vector drives etc. it is quite tricky to trouble shoot this.

I will start by investing in a proper DMM!

Any help would be fantastic!

Andy