Fanuc Tape Drill O-MC Spindle Resistor Overheat??

[John_B]

I have a 1990 Fanuc Tape Drill with the 0-MC control that alarmed with No. 2003 "Resistor Unit Overheat" while the machine was setting still for a couple of hours. The manual shows this to be the spindle resistor, and the solution is to let them cool. Checked and sure enough they were scalding hot.

I thought that these were regenerative braking resistors! Are they pulling current all the time while the spindle is stopped? If so, should I be hitting the e-stop when not working on the machine? I have several different machines with different Fanuc controls and have never run accross this problem.

Any insight would be appreciated!

Thanks,
John B

[cncdiag]

You should only have voltage across the braking resistors when the spinlde is braking.
Sounds like you have a problem with the regen circuit in the spindle drive.
Call if you need the unit repaired 813-983-1870

[John_B]

CNCDiag,

Thanks. I thought I might do some testing first to see what indicators appear. I finally got a chance to start it up and probe the resistor packs when running. With the machine idle I read 186 VDC across each terminal to ground, and with the spindle running I read 184 VDC to ground on each.

I did clean off the grate on the bottom of the cabinet that is the air duct to the resistor packs because it was blocked off about half way with crud. I have had the machine running for about the same amount of time as when it threw the overheat alarm, and the packs are cold to the touch right now (it's about 60 degrees here in Texas right now and they haven't heated up from ambient).

Does this tell you it may be an intermitent problem that you've seen before?

Regards,
John