Twin Reverb

[jnew]

I am completely new all over again. I've played and built Marshall plexi's FOREVER. I just picked up Fender Twin Reverb which has JBL D120F's. I know VERY little about Fender amps but want to learn what year this is and how it should be. The tremolo circuit does not seem to work but someone suggested that maybe the foot switch is needed?
I was told by the seller that it is a 73. It has a Silver Face and the Master volume does have a push pull pot. When I pull the Master out, is seems to get a little louder and maybe tries to break up a tad but sure is a very loud and clean amp. Beautiful tones and a lot of blooming jangle with those JBL's. I looked at all the pre-amp tubes and they look to all be 12AX7's except for one 12AT7. Not sure this is right. Perhaps U's guys could shoot me some thoughts on what to look for or confirm the proper tubes for this little guy.