Fortunately there's not a lot to go wrong. If you are qualified to safely go inside(high, deadly voltages in there), here's a schematic link:
http://esc73.midphase.com/~schehol8/fenderamps/princeton_reverb_aa1164_schem.pdf
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Signal flows from the plate of tube 7025, thru what looks like a .04mF cap, then thru another cap(500pF), to the grid of the reverb driver tube: 12AT7 pin 2. Pin 2 also connects to a resistor to ground. Signal continues from the plate(pin 6) directly to an intermediate transformer's primary. Careful. This primary has high voltage on each side. The secondary connects directly to the tank's input. If you can bang on the tank and hear it, then there's nothing wrong in the rest of the path.
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Any point along the way should show a trace if you can use a scope, a signal generator, and a multimeter. With the amp ON, and using a signal generator, send a signal that you can hear into the amp's 1/4" input. Trace along the signal path. When you find a point with no trace, you've probably found the bad component. Very dangerous inside there. Be very careful unless you know what you're doing!!
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Check these parts:
1) The tank can be checked with an ohmmeter.. set to check resistance. Readings in the range of 8 to 500 ohms can be expected on both the tank's input and the output transformers. Do this with the amp off and the tank disconnected from it. Dead short or no deflection mean a bad tank.
2) The 12AT7 should not be hard to find. I'd replace it.
3) I doubt if the transformer is damaged, but your signal trace should show a dropout if this is the problem.
4) The first 2 caps are only bad if the trace will not show up on both legs of the caps. Also check the soldering of the grid resistor.
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Old amps like this are also prone to broken wires and bad soldering. Re-pointing the soldering is a must on any rebuild.
Nothing else that I can see in the path. Again, don't go in there unless you know what you're doing. This thing can kill you!!
Good luck, Paul
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WUDAYAKNOW.. For the first time in my life, I'm wrong again!!
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