Need help finding a hum problem

I just got a new TT (Elipson) and hooked it up to my Counterpoint SA-7.1 pre-amp.  It's the first time I've used the RIAA stage in ~26 years, and the first time since I sent it in to Counterpoint for conversion to SA-7.1.

When I set the pre amp to RIAA input, I get this hum from the right channel.  Left channel is fine, and it is not a case of ground loop.  I swapped the tubes just to be sure and the hum remains in the right channel. 

I understand Counterpoint used a bad batch of capacitors at one time so I presume its one of these.  Question is, identifying which one.  Any helpful points or hints here?

There was a problem with the a stage capacitor but this was easy to spot: a very obvious leak.  That was replaced and the line stage works fine.