FET10e Channel Noise

[sparky54481]

Hello all! New user looking for assistance troubleshooting a fet10e. Recently right channel began "making noise". Narrowed down with O-scope to sinusiodal inputs resulting in 1/2 wave rectified output. Further checking, it appears the output transistors Q8, Q9 are not biased on (comp1 voltage is ~0.4v, while on good channel it is around 0.88v). I suspect component hfe drift, possbily requiring adjustment of pot or component replacement.

Anyone have any suggestions? Thx.

 

[Zen Mod]

Q8 and Q9 ?

on which schematic ?

this one ?

 

[sparky54481]

Yes, thats the one! S5541098.

 

[Zen Mod]

can you use that pic and write measured voltages in few critical places

the more the merrier

 

[sparky54481]

Troubleshoot FET10e

OK, much easier for me to make a little spreadsheet. See if you see what I am thinking - Q7...