need help, no current to y axis drive

[Jeffrey_Everett]

HI, my first post here.
machine: 1984 Burgmaster (big 4 axis mill) with Fanuc 6MB controller. The Y axis stopped moving, following errors started coming up (420). Upon following the Y axis wiring we found that the diode closest to the motor had shorted out because someone (not me!) stored a cutter head in the electronics cabinet and grounded out the live (male threaded) side of a diode. I swapped the unused B diode (no B axis attached) with the open diode but to no avail. My next step is to pull the wires off the Y diode and see if it's open, maybe I didn't get a good connection to ground when I installed it, then if it's open pull it out, and re-test it... If the diode is good and making connection, there's another problem.

We're able to handwheel the Y axis when physically depressing the contactor, so that, I believe, rules out fuses. The IO board is good. We swapped drive boards to no avail. I'm stuck now... I'm heading back over to the shop to test the swapped in diode. I'll post again when I get back. Maybe someone has run into something like this? I've got a rather large time sensitive project on the machine and am getting pressure to finish it quickly. Any help greatly appreciated.
Jeffrey Everett

[Al_The_Man]

What diode? I don't recall any diode in the Servo wiring, Only across a brake. Or do you mean in the drive?
I assume it is DC servo's?
Al.

[Jeffrey_Everett]

color me stupid, it was an insulator, of course it is open. Our tech guy told me it was a diode. I guess he was in a hurry to get home on Fri evening. It was pointed out to me the schematic by a visiting electronics engineer. duh...

anyway, the AC voltage arced to ground from the insulator and something is blown somewhere. As I mentioned earlier, it handwheels when the contactor is manually depressed. Got any ideas?

The tech guy is coming in tomorrow to probe around and see where he isn't getting 90 volts, as per an electonics guy that looked at the schematic today.

thanks, and sorry for the oh so wrong diode info, D'Oh! Geeze I feel stupid... lol

[Jeffrey_Everett]

right, DC servos, thanks!

[Al_The_Man]

Has the over load tripped on the contactor and requires a reset?
What alarm message do you get now when you power up? You should get one if the contactor is not picking up.
Al.

[Jeffrey_Everett]

I usually see a 401 servo error when pressing the main on button, but when I press the 2nd power button it usually goes away. At that point the machine is ready to home and available to the handwheel. If I try to home on the Y axis or try to handwheel the Y axis, I get a following error. Seems that no power is getting to the drive. I don't know about resetting the contactor. We had a different tech come in who checked the contactor coil and a few other things. I am assuming he knows about resetting the contactor, he is a cnc tech... After about an hour he gave up because he had to leave. OUr own tech guy is coming in Sunday. He's not actually a cnc tech, but he's good with electronics. He's going to try to track down the voltage loss. Later in the week the electronics engineer is going to come in if we haven't fixed it by then. He's also not a cnc engineer but he understands all the components. This machine is a bit of a dinosaur, but it's the only machine available to me right now that had a big enough table for this project.
thanks again for your input.