McIntosh MC2152 power amp technical question


My MC2152 suddenly acting up. When I use the XLR input the right channel makes popping sound when power off. To make the situation worst, the sound coming from this right channel is slightly lower compared to left channel which resulted in uneven sounds: left sound louder than right. IF I use the RCA interconnect the sound is fine and no speakers popping noise when powered off. I can settle by using the RCA interconnect and move on but i want to use the XLR input for better sound quality.  

Could it be the XLR right channel input connection defect? Or the electric board holding the XLR right input is defect?  Any technicians here in the community, your inputs would be greatly appreciated.  

thank you in advance for all your suggestions/help. 
kentrent
Audio Classics is an audio dealer/repair shop that specializes in McIntosh gear. They are in NY close to he McIntosh factory. Great reputation.
Hey....things go wrong with used tube equipment. Send it to Ryan at Audio Classics. He will have it fixed in no time. Because you bought it used, pay him a little extra to go through EVERYTHING.
Problem solved..
McIntosh is clear about it, the warranty is not transferable, the OP didn’t do his homework so he’s just a little surprised. If he had sent it to them like they suggested, and if it was clearly a manufacturing defect, they may have fixed it no charge but they weren’t going to agree with that without having it in the shop to see it. I would have dropped it off to Mac, talked to them in person, be nice about it and the result may have been very surprising. They have always been good people to work with and they do stand behind their products.