Soindle drive fault message

[fredhh47]

I have a late 80's-early 90's Bridgeport R2E3 CNC knee mill. Since it (the R2E3 control) stunk from day one, we finally decided to retrofit with the Centroid control. This was done by a 3rd party. The machine has operated very well since 1989, with occasional hiccups. The computer that the OS runs on is inside the control cabinet, which has caused some heat issues, which we addressed. The computer is running IBM-PC-DOS 6.x on a 386-DX2-66 system and the Centroid system self-identifies as a CNC7 when it boots up. So you know this is an old system.
A few days ago, upon starting the machine, I got a message saying "Z-axis full power without motion" and it went into a stop mode. I re-booted the system and that cleared. It ran fine for a few days, then the same message appeared. It also displayed the message Spindle Drive Fault detected" even though the spindle was not running. I don't know what is wrong and I don;t know how to find out what is wrong, either. The messages are not much help and the interpretations in the user's manual are cryptic at best. Regarding the axis fault message, none of the 3 suggested causes applies (as far asd I can figure out). They are:
1.) "Axis is against a physical stop' NONE OF THE AXES ARE AGAINST A LIMIT, NOR IS THEIR MOTION IMPEDED.
2.) "servo drive has shut down due to a limit switch input." (see #1)
3.) "The Z-axis home switch is the same as the z+ limit switch." HUH? This one stumps me because there is only one switch present for z-axis home and z-axis = limit. At least as far as I can tell. If anyone knows anything about this issue, I am all ears.

Centroid has told me that there is no way to upgrade to a windows based computer and there are/were no upgrades to the control software that would run on a DOS computer.
I cannot afford another retrofit.TOTALLY Out of the question.
I need this machine running - it has been a major workhorse in my shop.
Any helpful insights or suggestions will be very much appreciated.
Thank you
Fred

[fredhh47]

Sorry, I figured out that I contradicted myself on the age of the machine, I believe we bought the R2E3 new in the mid 80's and retrofitted it in the mid 90's. Not sure of the exact date. just wanted to clear that up.
Fred

[cncsnw]

What is the control serial number? It is probably in the 1000-series: e.g. between 1001 and 1600 or so.

What version of CNC7 are you running? The CNC7 version is usually displayed on the F7/Utility screen.

Do you have a VFD for spindle control, or do you have reversing contactors with an overload relay?

Also see http://www.cncsnw.com/ServoLogicPM.htm

[cnckeith]

sounds like the logic power supply has issues.

i remember the cable used to go from the logic power supply to the drive/plc unit would more often than not be the source of problems like you describe.

i would disconnect both ends of the cable, inspect them , spray with Deoxit https://amzn.to/3nTsZdD and plug back in and problem would be gone.

if not, then i would replace the logic power supply as next step.