Main Filter caps

[Ashroyer05]

I have 2 main caps on this psu. The board is completely out of circuit and the caps are still soldered in. I'm getting 145V across one and 145mV across the other. Should I get the closer to 145V across both? They are 200V 390microfarads.

[LLLlllou]

Re: Main Filter caps

I have 2 main caps on this psu. The board is completely out of circuit and the caps are still soldered in. I'm getting 145V across one and 145mV across the other. Should I get the closer to 145V across both? They are 200V 390microfarads.

Sounds like the bleeder/voltage-equalizer resistor in parallel with the cap reading 145V is open. You should read zero volts across both caps within a minute or two of removing power. These resistors serve two purposes:

1) Form a voltage divider to ensure the two series input caps share voltage equally.

2) Provide a high impedance path to discharge the input capacitors relatively quickly when power is removed.

High value resistors like these (they're usually several hundred thousand ohms) that have high voltage across them, often fail open circuit.

[Ashroyer05]

Re: Main Filter caps

Thanks for the lead I appreciate it. I will apply this knowledge.