Is the balance control centered on your preamp, providing equal drive to each channel of the amp?
Are you using ceiling fans that would cool the right side more than the left and or is the right side exposed to free flow of air, leaving the left side restricted?
If you look into these two things the next thing to do is check bias.
Are you using ceiling fans that would cool the right side more than the left and or is the right side exposed to free flow of air, leaving the left side restricted?
If you look into these two things the next thing to do is check bias.