4558 question

Tim Curtis vampope at swbell.net
Wed Mar 22 07:44:32 CET 2000

Hi Everyone -

I hope you'll pardon my ignorance, but I have a question regarding an Op
Amp in a Moog Prodigy.

I'm trying to troubleshoot why my Prodigy isn't working.  (It only gets
a thump at the output, oscillators can be turned all the way down - no
effect, VCA does affect the thump, VCF controls do nothing, I possibly
hear faint oscillators way in the background, if you have any ideas let
me know...)


The Op Amp at U22 is a 4558.  Shouldn't Pins 4 and 8 on a 4558 be the V+
and V-?  If so, is it wrong in a Prodigy (which has a +/-12V P/S) for
pin 8 to read only around 9 volts?  I'm not too smart, as you can tell.

If this is wrong, does anyone have any ideas where to look?  I'm trying
to actually figure this one out, for once...  :-)



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