Need Help!- Mitsubishi servo repair

[dm1try]

i'm trying to resurrect a mitsubishi J2 Super motor. here's what i have:

1. HC-KFS73 motor with a shot bearing, gives encoder error alarms
2. MR-J2S-70B amp with fried IGBT module
3. MR-J2S-70B-U005 amp, a high-speed special version for HC-KFS46 6000rpm motor

so i'm trying to make a working amp/motor pair out of this pile of junk. here's what i've done so far:

i've replaced the motor bearings and aligned the encoder locking the rotor with DC and rotating encoder wheel while looking at encoder count output. the encoder is absolute. the rotor locks at 4 positions (8-pole?). a got a target encoder count looking at 2 different HC-MFS43 motors i also have. after a bit of fiddling with the wheel it gives no alarms and count is continuous.

when i tried to jog the motor with U005 it jumped and the amp turned off with an overcurrent alarm.

then i've tried to swap power modules between 70B and 70B-U005, but damaged the PCB of the first one in the process... the U005 amp had a paper sticker with a f/w version on a DSP processor, while the regular one didn't. so i swapped those DSPs. not sure is the firmware is stored in there, tho...

with the replaced DSP the U005 behaves similarly. but i've investigated further and found out that:

there's an interval a bit less than a half-turn where the motor positions just fine. when i approach either end of this interval and try to step out of it the current (torque/load) rises rapidly with each step finally resulting in alarm. i've also tried to rotate the rotor 180 degrees out of this "good" interval and start moving from there - after the first positioning command the rotor started oscillating violently until i stopped it manually.

a nameplate on 70B and 70B-U005 gives the same max output frequency - 360Hz. with a 8-pole motor that's 5400rpm, while KFS46 motor has a max speed of 6900rpm. so it should be 6 poles or less, i believe.

unfortunately, i don't a have a good motor or amp, so i don't know should i damage the U005 amp further trying to make it believe it's a regular one or the amp is just fine and the motor has problems...

if anyone have any idea please help me... thanks!

[dm1try]

ok, got it working after all that unnecessary soldering iron torture. so yes, amps are exactly the same but U005 is programmed for 6-pole motor. and it looks like that those J2 amps can happily drive any motor within their capacity contrary to what mitsubishi does tell...
for anyone wondering how misubishi servos look inside

[ee_t]

Great picture, thanks for posting

[afh]

Thank you for the picture!

[dm1try]

thanks... some more pictures:
- encoder wheel pattern
- power module
- blown igbt
- DSP replacement
- endcap repair/bearings replacement
- damaged tail endcap before repair