[gridley51]

So what was wrong with the spindle drive?

[mflux_gamblej]

So what was wrong with the spindle drive?

A diode, and a wirewound resistor on the MTI-1 board had gone. The board was blackened a little near the resistor. I also replaced the caps on that board, but all of them measured OK before replacement.

Later after that repair, I programmed a M03 S4000, and didn't turn off the brake. The SCR that is on the MTI-1 board fried. I replaced that and the spindle runs - although the KTK drive isn't setup quite right. There is a serious overspeed, which I compensate for using a factor (see previous posts). CNC tapping works just fine like this and I wonder if the speed control using the factor (speeds measured with cheap laser tach) are more accurate than the factory setting. So, since that system works and has for more than a year, I haven't gone in to try and solve the overspeed issue.

[mflux_gamblej]

A diode, and a wirewound resistor on the MTI-1 board had gone. The board was blackened a little near the resistor. I also replaced the caps on that board, but all of them measured OK before replacement.

Later after that repair, I programmed a M03 S4000, and didn't turn off the brake. The SCR that is on the MTI-1 board fried. I replaced that and the spindle runs - although the KTK drive isn't setup quite right. There is a serious overspeed, which I compensate for using a factor (see previous posts). CNC tapping works just fine like this and I wonder if the speed control using the factor (speeds measured with cheap laser tach) are more accurate than the factory setting. So, since that system works and has for more than a year, I haven't gone in to try and solve the overspeed issue.

I know I posted something on another related thread, but the overall cause of the issue in the first place was that there was a diode in the CNC cabinet on the right side that didn't get soldered on at the factory. It was an open circuit, and just so happened to be a diode that controlled the machine's ability to operate the automatic brake. That is why the brake didn't shut off for me when I programmed M03 S4000, and trashed the MTI board, and so on as detailed below. silly, and serious all at once. 'thanks' bridgeport!