Audio Repair in NJ???

Lots of different google results for tube amp repair in NJ - mostly guitar amps but worth a call.

You don't say where in NJ you are. North or south.
Paul Delgado is Mt. Kisco, NY. Excellent tech.
www.marcaramusicamps.com

NYC  Analogique Service Lab.
http://www.analogique.com/

EBC Electronics in Manville,NJ. Email: ps@ebcelectronics.com. Address: 126 S. 14th Ave.,Manville, NJ  08835. Paul (Paval) did a great job repairing my Krell FPB 300. Very professional and reasonably priced. Hope this helps.
                Frank

You may have done all of the checks and balances needed, but I would advise that you at least check the balanced out against another source and If you don't have anything else, then grab some inexpensive rca to xlr adapters and see if that drives the amp. 

https://www.monoprice.com/product?p_id=4785

If you live in north Jersey try Bristol electronics in Ho Ho Kus. He works out of his house and is quite reasonable. He is recommended by major manufacturers.