Copland CTA402 Integrated Amp

My amp is sounding a little stronger on the right side than the left. The balance control is at the center. Could it be that one of the tubes are burning a little brighter than the others (especially the two right ones)? If yes, any suggestions on how to bias these tubes? Thank you in advance for your responses.
Swap the tubes from the right channel to the left. Does the weak channel follow the tube swap? If so, then one or both of the original left channel tubes are going bad. Swap the left and right channel tubes back to their original positions one by one, and listen for any changes upon each swap. You should be able to narrow down the culprit.

Of course, if the sound does not change after swapping the tubes, then your problem lies elsewhere...

Good idea. I'll try that and post my result. Thank you very much.
Has anyone done any tube biasing for this integrated amp? And how? Thanks.
Does anybody know if the Copland CTA 402 can be used as a preamp? I am looking to purchase a pair of monoblocks but want to hold off on getting a preamp at this time.