24V woes

I am trying to find the possible cause of a catrostrophic failure of my RAMPS board with Arduino and 4 Pololu stepper drivers having been destroyed. This setup was running on 24V, but with all of the normal precautions having been taken for high voltage use - no D1, 11 Amp PTC fuse replaced with 6Amp 30V fuse etc. and had perhaps 6 hours under power at 24V.
All of the steppers were running fine and I had just completed several cycles of ramping up and down the hot end and heated bed, both 24V, and these had been switched off for several minutes when everything went off. Investigation showed that there was a short circuit on a 24V line which I traced to the pololu for the extruder - the power supply had correctly folded back and had to be resterted. Without the extruder Pololu everything was fine, steppers were O.K. and display was visible. I then double checked for short circuits and replaced the Pololu. On switch on all four of the Pololus failed and the display stopped working. The Arduino won't talk to the computer any more either.

Has anybody experianced anything similar that may give me a clue what is happening here?

Further information: I used this printer for several years at 24V with a Generation6 controller and a separate 12V supply and thermocouple controller for the heated build stage, but have totally redesigned it with Ramps, LCD /SD reader. I was in the late stages of comissioning when this all went wrong.

Mike

I've read other people complain that their RAMPS had the wrong capacitors for use with 24V. Also, did you try talking to the Arduino when the RAMPS is separated from it?

The capacitors for the motor side are 35V - as this is a working value at 25 degrees and my board is cooled with it's own fan I would not expect any problem there..

Mike

You mean the stepper boards? How about the RAMPS board?

That is on the RAMPS board. There is a capacitor on the RAMPS for each stepper board, 100uF at 35V if I remember. The other electrolytics on the RAMPS board are 16V but are only fed with 5V from the Arduino. In any case, failure of the capacitors would blow up the capacitors, not the Pololu boards.

Mike