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This might not be the most indicated place, but I'll give it a shot anyway:

I have a Pioneer SX434 receiver amp (schematics at This is a great sounding amp so I'd like to keep it.
Here's the thing:
Right channel sounds ok but left channel doesn't. On the AWK-034 (power amp section) I replaced Q16 (2SC1318), Q20 (2SD131) and Q22 (2SB507) - all transistors went short - as well as R73 (18ohm 1/2W) - burnt out. I also checked R83 / R85 and R79 / R81 and they are fine.
But I still got no output. Instead it makes a harsh hum sound.

Am I missing something?


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Kev Thu, 10/01/2009 - 15:06

compare things to the working channel

check the power supply rails

work your way through the signal path
find the spot where things change

that pdf file you pointed to is a PCB layout and not a schematic
makes things a little hard to visualise the topology