TRA 8A-L Driver problem. (QT10ATC T3 -87)

My C axis servo Driver TRA 8A-L gave up yesterday on my QT10ATC T3 -87.
The boards has a OVC alarm (Over current I guess) and the load meter says constant 220-240%.
After a few restarts and the board operates as it should for a while (Loadmeter back to normal).

I tried to switch main board with XZ driver and the problem moves over to X axis so problem is isolated to the main board.
I will try to change all electrolytic capacitors on the board since thats the only components that actually goes bad by aging 32 years.

Anyone else have any luck with this by just changing the electrolytic capacitors?
I have repaired 2 spindle controllers (FR-SE) one of them by only replacing the electrolytic capacitors and one of them required new DK434 and power transistors.

Next step is to change the DKxxx but I dont have the time to wait for them

on some very old Mazaks I seen DC Servo Motors with brushes. People never change them, cause people forget to read maintenance manuals. It looks like old servo motor , with some black caps around it, closer to encoder location.

Good point there, maybe I should take the time to replace these if my servos has bruches.
But the current problem will follow if I switch circuit board with another driver so problem is on the drivers circuit board.

benganboll said:

Good point there, maybe I should take the time to replace these if my servos has bruches.
But the current problem will follow if I switch circuit board with another driver so problem is on the drivers circuit board.

Click to expand...

looks like the amp has a resistor 0.05 Om, and that is how it monitors current through the motor windings. Then, voltage taken from it goes into DK431, isolation amplifier. No idea what is inside, but I would guess, it converts voltage drop across this 0.05 itno logical 1. Sort of on or off. Then it goes altogether with other alarms into ALARM INPUT DIODE INTEGRATOR and the into ALARM LATCH. That amp is so old..., it could be any of this parts.

I never in my life seen electrical diagram for this TRA servo amp, only basic structure, maybe some people have it. I wonder if someone has it.