On Thursday, August 22, 2013 5:29:22 PM UTC-4, wrote:
On Thursday, August 22, 2013 4:15:04 PM UTC-4, Spehro Pefhany wrote:







I'd guess the VFD- it's presumably ~10 years old, about time for the



caps to be dying.







A couple of thoughts. I have a vfd on my lathe. When I disconnect the power the fan on the VFD continues to run until the caps are discharged. Have you noticed this? And if you have is the time before the fan stops shorter than it was.



I would check the DC voltage on the caps. Be very careful in doing this. Make sure the power is completely disconnected for say five minutes before opening the case. Then take a insulated wire with bare ends and put the ends across the big capacitors. Fasten the wire to some wood dowel or equivalent with electrical tape so you do not have to have you hands close to the capacitor terminals. Now connect your multimeter across the caps and set to high DC volts before applying power. Is the voltage about what you would expect? About 1.4 times the input voltage to the VFD.



Shut the power off and discharge the caps as above before disconnecting the multimeter.



Better yet is to get a friend who knows electronics and have him show you how to check the voltage on the caps.



Dan

Thanks.

--
PaulS