KD, you may need to go out of Philly to find someone you can work with that you trust. Google "vintage amp repair" and you will find quite a few. Good luck [img]images/smilies/icon_thumb.gif[/img]
I haven't lived in Philly for a few years, but there was Jerry's guitars on Castor Ave, Georges Music in Feasterville, 8th St. Music downtown, and Cintellis . I would contact these places and get some recommendations.
You can try the place where I take my guitars for repairs. They have several vintage guitars and amps in the shop, so they may be able to help you out.
Di Pinto's Guitars
631 N. 2nd St.
Philadelphia, PA 215-923-2353