Dead Reverb on SF Princeton, troubleshooting tips?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by loudboy, Jan 19, 2006.


  1. loudboy

    loudboy Member

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    I had this amp completely gone over last fall. Sounds great, but a few weeks ago the 'verb crapped out on me. I'd like to avoid a trip to the tech, so I'm going to look at it myself, in case it's something simple.

    I'll check the tank first - if it's not that where do I go from there?

    It's a SF, w/the pull Gain Boost knob.

    Thanks in advance,

    Loudboy
     
  2. slider313

    slider313 Silver Supporting Member

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    The first thing to do is check V2. The 12at7 is your reverb send tube and the 12ax7(V3) is your reverb recovery tube. Check that one next. If it isn't either, try the connections from the tank to the amp and see if there's a short in the wires. Usually moving them will pass/break the signal and you will hear it come on.
     
  3. Blue Strat

    Blue Strat Member

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    What slider said, but check the cables first, they're the most likely culprit. If you bang the amp with reverb up, do you get the normal reverb "crash"? If not, then the return cable, tank, or V3 is the problem. If you do get the crash, then the send side (v2, send cable, or tank) is at fault.

    If you have a pair of known good RCA cables, just replace the ones in the amp and see what happens. Proceed onward if necessary.
     
  4. Reeek

    Reeek Member

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    And when you're finished troubleshooting the cables, make sure you reconnect them properly. If they are bass akwards, the reverb won't work.
     
  5. loudboy

    loudboy Member

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    Thanks guys, I'll get into it tomorrow...

    Loudboy
     
  6. bob-i

    bob-i Member

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    Disconnect the reverb OUT from the pan, with the amp on and reverb knob up, touch the tip with your finger. You should hear a buzz, like you get when you touch a guitar cable plugged into an input. If not, replace the 12AX7 in V3.

    If that's ok, plug it back in, and unplug the reverb IN. Connect that to a speaker. You'll have to listen closely because the main speaker will be louder, but you should hear output from this. If not replace the 12AT7 in V2.

    If both those tests pass, the problem is most likely the reverb pan itself, they're very fragile.
     
  7. Dave Orban

    Dave Orban Gold Supporting Member

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    The little tiny wires that connect the cables to the springs (inside the pan) are VERY delicate, and can easily break.

    That's the FIRST place I'd look.
     
  8. Swarty

    Swarty Member

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    The first thing I do is patch an RCA plug jumper between in and out (remember the old Ice Cubes?). If the reverb control now works like a cheesey overdrive the problem is either with the cables or the tank.
     
  9. mr coffee

    mr coffee Gold Supporting Member

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    or sub a known good tank/cables (back it up to another fender amp)
    another fault of the later SF reverb amps is too low a cathode resitor on the shared cathode of the the 12at7.. it kills good at7's and finally will cook..
     
  10. fullerplast

    fullerplast Senior Member

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    Absolutely agree. This has almost always been the problem in my experience.

    You can re-solder them but be very careful, with low heat.
     
  11. donnyjaguar

    donnyjaguar Member

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    Agreed with others. My reverb kakked out when the spring broke. I was able to repair and re-spring, but this is not normally a user-servicable part. Budget $50 for another one I'd say.
     

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