Fanuc 6T spindle drive problem

[quizzze]

I have a Tsugami lathe with a Fanuc 6T-A controller. It has been stored away for about 2 years and I've resently began useing it.
Except from changing a couple of Eprom's and some bearings it started up fine and ran untill a week ago.

I had the spindle running at 500 rpm and no load, suddenly it stops and the spindel AL lights up. I opened the cabinet on the back and only found a 3 A fuse blown on the, I think it's called, PCB. I put a new one in and started the spindle. It turned about 20 degrees and stopped. This time the 3 A fuse and a 75 A spindle fuse had blown. I changed them and started again. This time the spindle turned for about 15 seconds then there was a noise from the spindlemotor just like it was being loaded and it stopped. This time it smelled burnt in the cabinet and there was a red LED ligthed, the second from the top. I belive it indicates a field loss or over current.

So far I have found that all of the 12 thyristors or SCR's to the spindlemotor are shorted. I spoke to the repair guy from the company I bought it from and he told me that they changed all 12 scr's 5 years ago.

He also told me that they put a new wire in their blown fuses. The first and third 3 A fuse i used where from them and the second was from Fanuc. Because the second one blow at once I opened the first one up and saw that wire was intact but it had come lose from the soldering point. He has probably put in the wrong wire and it got so hot that it came loose.

I've also found one resistor that might have caused the burnt smell. It's marked R437 on the PCB. There's three of them and they are wite and square but one is now abit black and were alot hotter then the other two.

I have no manual on the spindle drive, so I wonder if anyone knows what the 3 A fuse is protecting. It is marked FA2 on the PCB.
How come all of the SCR's are faulty, can it be that the triggering current to the SCR's is too high and cause them all to short?

Grateful for any suggestions
Quizzze

[gridley51]

Have you disconnected the spindle motor from the drive and metered it?It sounds as though you have had a flashover on the comm.
Better assess the motor and drive before starting to throw money at it.

[quizzze]

No not yet it will be the next step.
So far I've found a broken cooling fan and that there is seweral of wrong fuses everyvere, like a 15A fuse instead of a 1,3A. That could maybe turned a small problem into a big problem?

[Kevin Taylor]

I Have a chucker with a 3T and need some help on spindel bearing's . I think that the 3&6 controle share a lot of the same part's board's ect. there are a lot of them on Ebay and guy's that can fix or exchange I would isolate the motor and check for a short to ground and make sure the brushes are of I had a Axis motor that had a brush clear gone but it would still run just no power and it would alarm out Good Luck Kevin