Series 1 Limit Switch - E stop - Machinetek?

[kewl_cat]

I was just doing some routine maintenance on my Boss 5 Series 1. I have always had a little trouble with transistors popping occasionally. Once a month or so. I even went to all new MJ series transistors and all new 1N4003 diodes but it did not seem to change anything. Not a big problem as I keep a 10 pack at all times and could probably change one in the dark. I have been trying to tune up the machine a little. New oilers, 1 new(er) superior motor etc. I was just checking the SMS board for current dropout as Machinetek had mentioned in a post. The E-stop does work in this machine and I have used it. The ODD issue here is that when you hit the E-stop the current does not drop at all. Thru much time in the manual and some hair pulling I found a little non-Bridgeport wiring on the CR-1 at the #135 wire. I removed the wire and the current will drop to about .5A and then decay slowly. This machine has always been a little quirky on the limit switch but has always seemed to work. George, do you think this could be causing the occasional transistor blowing? I think the 135 goes to the E-stop and then to the 39 which is the 24V ground(I think)?. Anyone have any suggestions? thanks.

[machintek]

The purpose of the SMS board it to prevent a instantaneous drop of the current to zero. Typically it is the shock of transistors turning off that creates an internal short. It is now working correctly. Dropping to about half an amp and then decaying.
Where is T2 sitting as far as AC volts?
What kind of drive fuses do you have? Screw in or snap in?
Phase converter?

George

[kewl_cat]

No phase converter, 208V 3 phase,
Snap-in fuses, changed from the original screw-in
T2 is at 56V
The way it was wired there was about 10V on the 135 wire and about 15V on the 2 after I removed the extra ground wire.
Now there is about 13V on the 2 and 5V on the 135. The 39 wires in the back case has the same 5V. Is this right for the voltage or should the 39 be near zero?

thanks

[kewl_cat]

I chased the E-stop wire 135 from the CR1 to the e-stop and then the 39 wire. The 39 wire which is ground always has voltage on it. Going on the assumption that it should not since it is a ground I kept pulling wires to find the 'voltage leak'. I ended up under the panel where the 24V and 56V transformers are located, plus bridge rectifiers and capacitors etc. Just checking voltages I noticed that the 56V capacitor which I think is C1 on the schematic has the same voltage on both pos and negative. Since the other capacitors had 0 on the neg and some other voltage on the pos should I assume the Cap is bad? No fancy test equipment here but it seems to flow both directions. Do caps go out in this manner? The only experience I have had is when they go out and leave an open circuit. If this cap is bad then do you think it could account for the occasional transistor pop? And I also occasionally pop a bridge rectifier on the X,Y & Z axis. Maybe this will eliminate some quirks

thanks for all your help... -rob