Sansui au 9500 unbalanced left right channel

Hello every sansui fans, my au 9500 has unbalanced channel,
here are what i have already done:

1)i recapped the capacitors for the pre amp,driver board,eq board
2) recapped the 4700uf and 1000uf capacitors
3) cleaning the dirt with contact cleaner on the switchs and knobs
4) i plugged my mobile with rca into main in and sounds excellent for both channel
5) i changed the transistors of 2sa726 into 2sa733 no pops or cracking now when in/decrease volume.

I plugged my cd player and play music into aux and put the preout main in jumper back and test with speaker of system A.

Now the right channel sound very weak, left channel was fine.
But until i exchange the F 2030 pin 1grey color with pin 2 blue color. see pic.

The right channel change back into normal sound and with better sound. The left channel became weak channel.

How can i solve this problem?

Thank you very much.

Welcome to AK, I am sure the experts will be along shortly.....

Anyone know how does au 9500 actually work after power on?
so i can determine the possible error parts.

i have changed the relay into omron dc 24v modle, but still the same.
i have tried resolder the preamp board. the weak channel now a bit louder now but still weak.

Anyone experts would help me?

Deleted I just realized you already tried that.....
Adding something back in.
The level control pot on the back plane. I have had that pot cause the same issue on my 2000x,5000A,5000x's over the years. This is of course if the outputs are balanced and normal when playing through the MAIN input using a separate Pre-Amp which means the power amp section is not the culprit. Sometimes the Deoxit solves it and other cases it has not.

Example: The 5000x I am rebuilding had both channels out of bias and the voltage on the right channel was only 23v of the specified 40v and the volume level was still fairly well matched to the left channel which was cracking and popping with DC leakage.

Thank you for reply. i will try that pot tonight.

Cleaned the pots but sound still weak on one channel
Would the transistors on preamp board would causing the problem?