Need Help!- Fanuc 11m Spindle drive code 11: "DC Link Voltage High"

[cwtoyota]

I recently purchased a Kuraki KV-700 VMC.
The machine has a Fanuc 11M control.
The spindle drive top board is A020B-0009-053

I have the following alarm when I start up the machine:
"EX050 Spindle Volt Excess"

Kuraki manual says:
"The D.C. Voltage of the SMDU power unit is abnormally increased"

So I opened up the back cabinet and I see that the diagnostic LEDs on the spindle drive top board are lit up 8, 2, 1 which I have discovered is Fanuc code 11 "DC Link Voltage High".

Through searching this site and the net, I have determined that there seem to be four possible causes:

1) Possibly bad fuses on the spindle driver? Which ones and where are they located? What would cause these to blow?

2) Possibly a bad Spindle Driver. I've read about some bad transistors. Which ones? What is the test procedure for these?

3) Possibly my power is uneven between the phases. I have a nearly new Temco 7000-21 phase converter running on 208 volts from a buck-boost transformer. I have also tried the machine on direct 240 (no transformer) with the same results. I have noted that the voltage between L1-L2-L3 varies by as much as 8-10 volts between the pairs of legs, although it doesn't fluctuate more than 1 volt. Could this mismatch between the phases cause the alarm I'm receiving?

4) The machine is and has been in a somewhat cold / humid environment here in NW Washington state. It is in an unheated shop for the time being until the heat is installed. I read a thread that suggested that some Fanuc drives may not function correctly when the conditions are cold and high humidity.

Any and all help is appreciated greatly. I have been away from CNC machines for almost 10 years, and have to re-learn a lot of things.

[cwtoyota]

Still trying to trouble shoot this if anyone can help:

I've Eliminated possibilities 3 and 4 from the above list.

The power between L3 and any other leg is 5% higher due to there being no load on the phase converter. This is stated very clearly in the Temco documentation.

I warmed up the machine with a heater and there seems to be no change in behavior.

I checked the fuses on the spindle drive top board and in the box all are good.

Seems that I likely have a bad Spindle drive.
Anyone know how to test these transistors?

The wierd thing is that occasionally (it's rare) if I keep trying I can get the machine to start for a bit. Long enough to home the all three axis. So it can't be completely bad.

How do I test this spindle drive board and box?

[cwtoyota]

So I called Fanuc. The tell me that I need to test resistance between the B C E terminals on the transistor modules. I will give this a try this evening. Aparently the transistor modules are pairs of two transisters per module. If the terminals are shorted, they are bad and need to be replaced. Also, if they are shorted, they warned that the top board will also be bad because the shorted condition takes out the top board.