spindle amplifier

Hi all,
I am currently working on a mori seiki sl-25 lathe and we had a short to gnd on a fan that was tied to the main cb of the machine that blew one of the fuses and single phased the machine after the short was repaired and disconnect fuse replaced the spindle amp was giving al-12 immediately when a jog or run command was issued, even with the motor leads disconnected it did this. Got on the phone with fanuc and they sent me a top board and 3 igbt modules, with very vague testing instructions for testing my existing ones for shorts between b,c,and e. I have not found any shorts, and there test has me checking with the jumper bars installed and motor leads removed. Anyone have a better procedure for testing these modules even if it means removing all jumpers/wires? Sorry if this isn't in the right section or is already answered I appreciate any assistance I can get!!! I have lots of experience with smaller servo amps but this is my first shot at a spindle amp of this age!

Btw amp model is a06b-6055-h422

First, I've never ever seen a fan come off the main without protection in the middle somewhere on any mori. I'm guessing the drive itself blew, taking out a fuse. You probably only found the bad fan diagnosing what happened. I've always had to take all the leads and jumpers off the igbt's to get a good reading.

Hi
First thank you for the fast response! Heres some more info, I megged motor leads u v and w to gnd an got around 800 megohms. Hooked up motor to power and it runs.
The fan was fused at fifteen amps but for some reason it blew one of the mains before it blew, i do know the first time they replaced the main fuse the fan sparked and blew its fuse. Anyhow that said the machine was likely in cycle when it was single phased and there are burn marks on the back of the spindle top board. Sorry for all the Q's but in checking these what type readings should I expect to see?

Thanks so much!

Hi
so i found two bad igbts and replaced them
I turned on machine gave jog command with motor leads disconnected
and got al-2 as expected on drive connected leads and gave
motor jog command and motor started then cut off and gave
al-12. I removed motor leads and tried again and was back to al-2
so I guess motor is bad but it's funny it will still run. guess
windings are just bad enough to cause problems.

any thoughts?
thanks lots for the help!

Hi,
Sorry havent been online for a few days but for anyone following this the issue was resolved by replacing the igbts and the motor, the motor was megging good to ground and between coils but the actual winding impedance was abit low on u phase coils, hence higher current draw and short circuit alarm.

Thanks and good luck