I don't think the problem was with tjhe PS . It could be from a couple other things.
1. Bad connection on the disable line or a bad switch
2. A bad connection on the charge pump line
3. A glitch in the PC that is causing the 11 Khz singal to drop out
If you flip the charge pump switch to off and it goes away then its probably number 3. Since you switched to an old PC that probably verifies number 3.
Dan
www.camtronics-cnc
I have the latest G540's in stock with the recent mods to the sense lines and the new trim pot location.