Long story short - a KA-3500 that made a horrible hum, pop, scratchy sound at power up, then random pops when playing.
Did the switch cleaning routine, replaced vol pot, full recap, all to no avail. Set it on a shelf for a couple years.
Decided it must be the differential pairs - nope.
I decided to replace all of the transistors except for the 4 outputs and the 4 FETs with what I had on hand. Here's what I used - would appreciate knowing if I made any absolutely horrible choices that should be redone.
PS - The nasty noises are all gone! (The drivers seemed to be the culprits) DC offset is -28mv and -35mv. It sounds really good to me.
qe1-4 2sa620wn > ksa992fbu
qe5,6 2sc1885 > ksc2383yta
qe7,8 2sa620wb > ksa992fbu
qe9,10 2sa733 > ksa733cyta
qe11-14 2sc945 > ksc945cyta
qe15,16 2sa733 > ksa733cyta
qe17,18 2sc1735 > ksc2690ays
qe19,20 2sa850 > ksa1220ays
qe25, 27 2sa673 > ksa1220ays
qe26 2sc1222 > ksc1845
Preamp
q5-8 2sa640 > ksa992fbu
q9,10 2sa872 > ksa992fbu
Seems like a lot, but really only $4-5 in parts.
Thanks
Did the switch cleaning routine, replaced vol pot, full recap, all to no avail. Set it on a shelf for a couple years.
Decided it must be the differential pairs - nope.
I decided to replace all of the transistors except for the 4 outputs and the 4 FETs with what I had on hand. Here's what I used - would appreciate knowing if I made any absolutely horrible choices that should be redone.
PS - The nasty noises are all gone! (The drivers seemed to be the culprits) DC offset is -28mv and -35mv. It sounds really good to me.
qe1-4 2sa620wn > ksa992fbu
qe5,6 2sc1885 > ksc2383yta
qe7,8 2sa620wb > ksa992fbu
qe9,10 2sa733 > ksa733cyta
qe11-14 2sc945 > ksc945cyta
qe15,16 2sa733 > ksa733cyta
qe17,18 2sc1735 > ksc2690ays
qe19,20 2sa850 > ksa1220ays
qe25, 27 2sa673 > ksa1220ays
qe26 2sc1222 > ksc1845
Preamp
q5-8 2sa640 > ksa992fbu
q9,10 2sa872 > ksa992fbu
Seems like a lot, but really only $4-5 in parts.
Thanks
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