pioneer A400

[glennjarrett]

hello im glenn and new to this forum . I have a pioneer A400 the problem is the right channel is very low with distortion the left channel is fine . i have checked the output transistors on the right and they are fine the bias wont adjust on the faulty channel either, i have injected a audio signal in to the decoupling caps so to rule out the volume control and its still the same you can hear the music but it is very low volume and clips (distorts).at the speaker outs the voltage across the L/H channel is 13mv but the right it's 235mv !. As one channel works fine i have not touched the power supply. the test points at the driver transistors give the same reading on both channels, would really appreciate any input please .

[nigelwright7557]

Sounds like a driver, Vbe multiplier or VAS fault.
Check the transistors by removing them and while they are out check the resistor values in that area.

[sakis]

there is a possibilty that you are looking for a shorted transistor while the problem might be an open transistor
for starts schematic is available em ail me to have it

the A400 features a seperated power supply for the first stages of the amplifier ...there is a very good posibility that fault lays there

you need to verify all voltage according to the schematic first