PHONO pre amp is source trouble. ( X1 & X6 )
Try C3 & C8.
Check the 25V line. There should be a lytic cap there, change it.
Without signal check the voltages on X1 & X6 be sure they are very close.
If one is leaky it could effect the "good" channel & make both bad.
Used to happen to cheapo stereos in the 70's.
Be nice if you could post schematic of power supply area also.
Zeno
