Re: Princeton reverb reverb tank
Did the reverb go gradually or all of a sudden? If you are using the Reverb/Tremelo pedal, try disconnecting that.
Not to be difficult, but did you move/drop the amp right after playing it while the tubes were still hot? Tubes don't like that.
Make sure that the reverb cables are tight in their connections both at the tank itself and on the back of the chassis.
Try tapping
lightly on the reverb tank itself. If you don't hear any sound then (you're moving the springs with the tapping), then either the tank is damaged or the reverb recovery triode is dead. Try swapping out the reverb recovery 12AX7 (V3) with a known good tube.
If you do hear reverb sound when you tap but not when you play, then the problem in the circuit is before the tank. Try another 12AT7 in the V2 spot.
If it's not tubes and it's not cables, it could be the tank itself. The little transducers at either end can be pretty fragile and you can't really fix them. Good news is that a drop in reverb tank is less than $30 at tubesandmore.com or mojomusicalsupply.com. Ruby makes nice, beefier replacements for the same cost as the Accutronics tank. Just make sure you get the right part #: 4AB3C1B (or equivalent).
All that said, if you still have a 2-prong plug and a functioning "Ground" switch, get thee to an amp tech - now! Seriously, that thing is a shock hazard as is. A good tech should know how to wire a 3-prong plug and bypass the Ground switch. Make sure he gives you the old power cord and leaves the switch in place. Also, if the electrolytic caps (power filters and cathode bypass caps) are 37 years old, they probably should be replaced. A bad cathode bypass cap could explain the bass-ey sound and loss of volume. (remember to ask for ALL of the original parts back - some audiophool might pay your kids big bucks for the amp if they still have all of the original components, no matter how much goo is dripping out of them
)
Hope this helps,
Chip
