[Amps] Strange power supply

[Will Matney]

Peter,

He said though, "60 cycle?". He isn't for sure what the frequency of the hum is. With one diode open, you would essentially have a half wave power supply only conducting on every cycle. If you have a filter going bad to the point it isn't filtering the AC, then you would have a 120 Hz hum. The hum would grow greater under load because the filters aren't charging up to support the supply. Thus, you'd have a greater voltage drop since the filter caps control the voltage sag along with the transformer. If the filter caps were all good, and you put a half wave rectifier to them, I'm not sure it would sag that much. I would check to make sure that the screws used to mount one of those panels didn't puncture the side of a filter cap since his problems started after applying the wood panels. A screw could have cut a trace in two on a PC board, or could have damaged a wire inside. I just can't see a rectifier going open just setting.

Best,

Will

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On 4/20/06 at 11:39 AM Peter Chadwick wrote:

>Like Peter, I would suspect one of the diode stacks has gone open
>circuit. If it was the filter capacitors, the hum would be 120Hz.
>
>If it was the cat, the hum caused by purring is modulated at a lower
>frequency!
>
>73
>Peter G3RZP
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