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In Reply to: RE: Interesting new development ..... posted by vinnie2 on July 17, 2014 at 16:36:05
There should be no additional drop moving the B+ take off from pin 8 to the center tap. Your 5 volt winding is shot. Try using 1N4007 diodes instead if the 5V4G.
Follow Ups:
You are right, the voltage is the same. I hooked it up the standard way and got the lower voltage again. The only other thing I changed was to put two big 40 mf oil caps in place of the twin 50mf 'lytic I had for filter caps. Could they have dropped the voltage that much?
In any case, I guess I will still go ahead and build the separate power supply and see if I can get rid of the hum.
Edits: 07/18/14
Going from 100uf to 80uf will not drop voltage. It sounds like you have some parts problems. Are you using old, recycled parts? Use your ohm meter and measure your power transformers resistance on the different windings. If you have a capacitor setting, measure your caps.
It's not the value of the caps that I think dropped the voltage but rather the fact that they are old stock oil caps instead of 'lytic. I have a cap checker and I checked them a while ago so I think they are good, but maybe I need to check them again to be sure. All other parts are brand new. If I put the 'lytic cap back in the voltage goes back up, so I think it's the oil caps that is doing it. I used these same caps in a previous amp with no visible problems.
Edits: 07/18/14
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