This BDS4 servo driver (Kollmorgen / Cininatti Milacron) has low torque. I am 100% confident it is not the servo itself (swapped).
At rest (idle state) the servo already has low torque so I am still able to turn it (although with resistance). So it cannot be an issue with the control signal from the computer (or a software setting) as this has to be 0 volts on C1/11 - C1/1) in idle state.
Are there any experts on here who know this device inside out?
10kHz / 320Vpp arrive on the Ma,Mb,Mc terminals, PWM duty cycle is only about 38% when idle (compared to 51% on the other 2 BDS4). So the 6 IGBTs working as they should (they also measured good). It can ONLY be a timing issue! Either PWM duty cycle too low OR something is wrong with the phase-shift between the 3 signals (hard to investigate with my equipment here at the moment, only having available a 1-ch oscilloscope).
Trim pots:
STABILITY: fully CCW (min)
CURRENT LIMIT: fully CW (max)
COMMAND SCALE: fully CW (max)
BALANCE: adjusted to 0 volts across C1/11 and C1/1
Jumper #35: I-J + K-L (DEFAULT)
Jumper #28: 1-2,3-4,5-6,7-8,9-10,11-12 (DEFAULT)
DIP-Switches A to L: 0000 01111111 (1024 lines, wide marker pulse DEFAULT)
BDS4-COMP3 Board (BDS4COMP3310414W Rev. A):
DIP 1A: 1,2,3,4,5,6 - all up
DIP 5A: 4,5,8,10 - down, rest up
I am not sure what this COMP3 board is for and the meaning of the settings. It's purely passive and will probably compensate some kind of reactance, possibly inductance from wires and coils (from the servo resolver?).
Someone previously did some repair works on that PCB already, so it is possible that an adjustment has to be corrected. However, I have no documentation on those 8 trim pots inside (AZ, AGAIN, CZ, CGAIN, OSCG, R/DTR, R/DG, R/DZ) and can only guess their purpose. With the exception of R/DTR the seals (locking paint) seem to be intact. Turning this pot R/DTR (powered up state) didn't make any difference, so I turned it back to it's original position.
If something is broken on the component level I might be able to find and fix the fault. Electrolytic capacitors have already been replaced recently, with the exception of the tantalum caps.
Does anyone have a schematic for the BDS4 ? That would help me a lot.