Zapco Z400C4-SL

I'm working on this amplifier and need to find info on some semiconductors that zapco used in this thing. They are to92 type and they are on the front end of the amp. The part numbers on the transistors and locations on the board are; Q41-c436aj, Q48-c436aj, Q49-c448ab, Q54-c436aj, Q55-c448ab, Q60-c436aj, Q65-c448ab, Q72-c448ab. I've tried to cross them and find data sheets with no luck.  With them out of circuit, two of the three legs show about 4ohms in either direction on both types and on the exact two legs. The middle leg to the third leg shows high resistance. I'm stuck. Don't know if they are regulators or some kind of mosfets or just bad transistors. The four 100uf caps in the same section did leak their electrolytic fluid. All the surface mount transistors in the area do not show any shorts.  Would like to know what could work in there place. Any help would be greatly appreciated.

Scott

The caps did leak and replacing them is all that I did. THEY DID NOT DAMAGE the board.

I found a timing issue with a HCF4093 QUAD 2 INPUT NAND SCHMITT TRIGGER located at U20.

The 10uf 50v cap (C72) connected to pins 12 and 13 was making the amp not start all the time. I found this when I removed the cap and the amp started every time. I opted to put a 100uf 50v cap in its place and everything works fine.

So after replacing all the out-put finals, power supply MOSFET’s, full wave bridge, all 12 SMD op-amps and many caps, it turned out to be just the four leaking caps in the preamp stage and the timing issue. It sucked working on a four layer board without a schematic!, THANKS ZAPCO FOR ALL YOUR HELP! (NOT). Just thought I would share.

Back together…