Fried servo amp, why?

[DennisCNC]

What do you think happened that cooked the power stage in this amp like this?

http://img128.imageshack.us/img128/9034/bhlsxs8.jpg

http://img128.imageshack.us/img128/2346/bhls2yt8.jpg

The machine was running good then one day bam it's dead. The place wants ~$4k for a new one.

It's a BHL servo amp with resolver feedback. I still need to check if the wires to the servo motors didn't short or the motor it self. But the drive had over-current protection so that should have saved it, maybe.
The power transistors look good from out side not like the ic's.

Thanks

[DennisCNC]

Can the IGBT's be test in circuit?

[Al_The_Man]

In many cases the cause of output stage blowing is faulty firing circuitry, causing a IGBT to fire the same time as an opposing one in the bridge etc.
This causes a dead short, the IGBT's can generally be checked with a meter but are best removed for accurate testing.
It looks as though there is lower power IC damage, usually replacing the IGBT's without first testing the firing circuits, result in blowing them again.
Al.

[DennisCNC]

Thats for the insight, Al.

I was thinking of getting all new chips and re-checking all the resistors and caps and IGBt's in the power stage. New components and igbt's are around $90.