First time poster with QRX 5500A

[crkeith54]

I hope this is the proper forum to ask for help. This is my first quad repair. I have a Sansui QRX-5500A with F-2048 and F2084 quad boards. The amps are good and I have good sound whether I input to front, rear, or both as long as I have the function switch in 2-ch or discrete. All other function positions produce very weak audio with cracking and popping. With F-2048 pulled I get the same very faint audio but none of the cracking popping sound on all functions except 2-ch and discrete which sound great. I have read about noisy transistors on the F-2048 board. Would this be the case here? If so, any transistor in particular since there are I think 16 on this board? What else should I look for? All switches and pots have been de-oxed and all other functions seem to work OK.

Here is a link to my SM:
http://akdatabase.org/AKview/albums/userpics/10007/Sansui QRX-5500A, QRX-7500A Service Manual.pdf