where to start?

[advt001]

I have a 91 4020ht which has been very reliable until now.After a normal shutdown the other night. I come in this morning and upon switching the disconnect to the on position sparks flew ,it blew the main fuses.Now electricity is not one of my strong points so I had a maintenance man look at it.My guy said that although he is not sure what the problem is there is definetly a problem.He said there is not any resistance from leg to leg any didnt show anthing to ground as well.I have searched the forum and cant find any remote ideas.Would you please help me if you have ever experienced this or have an idea where to start?

TIA,
Scott

[CHAD LAWSON]

I have had a siemens 611u servo system power supply do this before. It was fused on the incoming side and once powered on the fuses were blown. So when you tested anything there showed no short due to all the fuses being blown. I would start with anything that is fused down off the incoming power or goes through a contactor that may be engaging at power on. I have not ever worked on these machines so can't even imagine what you are looking at. One thing i know about electricity after ten years is it does weird things.

[carbidecraters]

91 4020 will not have the semens system. You will have to get good with electricity or get an electrician in to check you input voltage and wiring.

[denmar]

Since the Spindle driver is the only that uses the 3 faces power; disconnect the three
wires from the transformer to it and try power up.

[advt001]

I had an EE in the shop today and it took a couple of hours to determine the problem was something called a carbon trace on the 1170 board.85 dollars for a new board.Thanks again for the comments.

[carbidecraters]

Oh if you need one I have a spare 480V laying here.

[advt001]

Carbide, I appreciate the offer but I got it covered this time thanks again.