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I'm working on a 1960 Fender Concert amp. Somewhere along the line someone replaced (among other things) all 6 diodes in the rectifier string. On one leg, one of the diodes is reversed. It's the last one where the two side meet. The amp has been working apparently. I will, of course, replace the diode. What problems can or could this have caused? I'm kind of surprised it works so well.....
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If the last diode in the string of three is reversed it will block the dc voltage created by the first two, so the B+ will be reduced because only one half of the ac secondary is being sent to the power supply.Originally posted by Daver View Post
I would meter test the backwards diode to be sure that it is in fact in backwards and not just marked differently. Also measure the dc before and after the replacement and see what happens to the voltage levels. -
I've seen this before too. Even a case of original work from the factory. You end up with a half wave rectified power supply. Lower B+ voltage as already mentioned plus more sag (in a bad way because excess ripple at 60 Hz is generated) and lower power output.Comment
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Thanks, guys. I tested the diode and it's marked correctly so it was in backwards. I didn't measure the B+ before replacing it. I was in too much of a hurry to make it right.
One of the problems and complaints about the amp was that it was really bright and somewhat thin sounding. It does sound better now. Guess that had something to do with it.
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