[sdiy] Prophet 5 -15v rail is shorting... Need advice

[Oakley Sound]

It is very unlikely that the Polysix transformer will power a Prophet 5. 
The current draw on a Prophet 5 is almost certainly larger than the 
smaller Polysix.

However, the Polysix does have its own +5v rail derived from its own 
transformer winding. The Prophet derives all of its power from the 
+/-28V voltage lines so needs a big transformer that has to provide the 
current for the +5V6 line as well as the +/-15V. This results in far 
more heat dissipation than a well designed triple output supply.

It is very possible that the variation you see in the output of the +15V 
regulators is due to your transformer not able to supply the correct 
voltage at that current. But I would need to know the input voltage to 
the regulators to be sure of this. To function the regulators will need 
at least 2V5 across them, ie. input voltage - output voltage > 2.5V.

The transformer in a Prophet 5 can be any equivalent sized device. There 
is no need to get a proper SCi one. From memory I think I used toroidal 
22-0-22V at 1.5A when I replaced my humming transformer in my old rev 
3.2. But you should check this on the Prophet 5 service notes.

I think Wine Country will be able to supply a new transformer for you. 
But personally I would fit a quieter toroidal type.

Tony

www.oakleysound.com