Another 4558 Question

danial stocks diode at
Thu Mar 23 15:19:16 CET 2000

>I just resurrected my Moog Prodigy from the dead - it was the 4558 Op
>Amp at U16 if anyone cares.

This sort of thing is quite common... I have repaired quite a few vintage 
synths and offer this advice.. If nothing seems to be broken, but it still 
wont go, change all the op amps... It seems that many chips manufactured in 
the 70's especially plastic pack ones are now at their end of useful life.. 
most likely from poor sealing of the package resulting in the chip 
metallization corroding [aluminium connections on chip].. as op amps are 
cheap, I'd recommend replacig them all... it could even be another decade 
before another blew in the synth, but it could be next week...
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