You may have shorted power diodes, shorted power
transistors and shorted capacitors in the power supply. As a
result the supply keeps trying to start-up but senses a short and
shuts down and repeats continuously, hence the voltage on the bulk
capacitor jumps up and down.
On 2012-07-13 1:02 AM, mickeyaslam
wrote:
toggle quoted message
Show quoted text
Hi Jay,
Thanks for your suggestion but it didn't work. I am pretty sure power supply is the problem. Maybe something has to do with start up circuit, since power supply tries to start and then shuts off. One thing I noticed is that the voltage on the input bulk cap (470uF, 450V) is not stable and jumps ups and down(should have been stable DC). Maybe something has to do with power factor correction circuit. not sure need to do further investigation. Maybe something not working in the OV and OC protection circuit.
mickey
