[sdiy] Prophet 5 power supply news...

[Oakley Sound]

 > So can we assume that simply the Polysix transformer
is not up to task ?

I would not expect this transformer to work. The P5 is full of older 
NMOS electronics, and has far more analogue componentry than the Polysix 
and takes a lot of current.

What is the voltage at the input of the regulators while it is connected 
to the P5 electronics? This will be the voltage across the smoothing 
capacitor. It needs to be a minimum of 17.5V. If you have a scope this 
value should be the lowest part of the waveform, for the positive side.

Note: A DVM on its DC ranges will not measure ripple so you have can't 
assume that the voltage is actually what is says.

How much ripple have you got under load? Measure the AC voltage across 
the smoothing caps. Really it shouldn't be any thing larger than 3V.

Tony