NSM Performer Grand audio problem

I admit I am stuck in the 1950's so I have little experience working on this era jukebox and also the NSM brand. I believe upfront that the amp probably needs to be gone thru. Having said that I am getting distortion in the right upper speaker and somewhat compromised sound thru the entire sound system. This started with a loud base pop when first turning the machine on and occasional distortion in the speakers that would clear up as it played for a while. I would like some direction trouble shooting and the name of some who has experience with rebuilding this era NSM amp. Many thanks. The Record Machine

Hi
Usually the nsm amps are fairly durable, the pop sound is fairly common on nsm machines, have you tried switching speakers to see if problem transfers. The upper speakers are accessable the bass speakers are difficult to get at. I have a machine like that myself and if i had problems like that i would try recapping the amp or more likely get a replacement amp, the amp in the wall mounted nsm machines is the same and should be readily available, common enough in Europe not so much in the US
clones