Reverb stopped working (Princeton)

fandangofandango Frets: 2204
As thread title. For some reason the reverb has decided to stop working.

All the valves light up.
Twiddled the reverb knob.
The foot switch soldering looks okay. And is connected properly because the tremolo switches on/off.
Tremolo works fine. 
Thought it might have been the leads (as I had removed the reverb tank to fit new baffle) so checked those. Even swapped them around, just to make sure. No effect.
Removed and checked the tank, which looks fine, but can't test it in another amp.

The amp occasionally pops and fizzes for a few moments before settling down. 

Am now at a loss ... can someone help?
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Comments

  • ecc83ecc83 Frets: 1589

    Does the amp 'CLANG' when you kick it?

    Dave.

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  • ICBMICBM Frets: 71952
    Is it a modern Accutronics tank? If so it's almost certainly a broken coil wire at the return end, they're notorious for it. You won't be able to see it, it's on the plastic bobbin where it bends over the edge to wrap around the terminal pin.

    If it is, replace the tank with a TAD/Ruby one, they don't have the design fault which causes this.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • p90foolp90fool Frets: 31367
    As @ICBM says, with the added bonus that the TAD tanks sound a little better too, a touch darker and fewer ringing overtones. 

    Having replaced one out of necessity, I'd now do it as a matter of routine because it's a great cheap upgrade anyway. 
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  • FunkfingersFunkfingers Frets: 14321
    edited June 2018
    fandango said:
    Thought it might have been the leads (as I had removed the reverb tank to fit new baffle) so checked those. Even swapped them around, just to make sure. No effect.
    • Clean sockets on reverb tank and amp chassis.
    • Test with alternative reverb send/return leads.
    • Inspect innards of reverb tank. Something could have become detached.
    • Substitute V2 and V3 (one at a time)


    Duh! Too slow (again).
    Be seeing you.
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  • ICBMICBM Frets: 71952
    p90fool said:
    As @ICBM says, with the added bonus that the TAD tanks sound a little better too, a touch darker and fewer ringing overtones.
    I recently replaced an Accutronics in a Two Rock, and thought the same thing. The Accutronics sounded tinnier - when it was working, the fault was intermittent - and the TAD sounded both slightly darker and also deeper, as in just having more reverb.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • fandangofandango Frets: 2204
    ecc83 said:

    Does the amp 'CLANG' when you kick it?

    Dave.

    If you mean whether the reverb tank does that trick where it makes a disturbed clash-doing noise? No, it did’t when I just tried it a few minutes ago. But it has done in the past, but only when accidentally knocked, of course.

    ICBM said:
    Is it a modern Accutronics tank? If so it's almost certainly a broken coil wire at the return end, they're notorious for it. You won't be able to see it, it's on the plastic bobbin where it bends over the edge to wrap around the terminal pin.

    If it is, replace the tank with a TAD/Ruby one, they don't have the design fault which causes this.

    The tank is a stock Ruby a RRVL 2AB1C1BV3. Are they any good? Is this type prone to the problems you mention?


    • Clean sockets on reverb tank and amp chassis.
    • Test with alternative reverb send/return leads.
    • Inspect innards of reverb tank. Something could have become detached.
    • Substitute V2 and V3 (one at a time)
    Sockets okay.
    No spare leads, but tested continuity of existing leads, and they’re okay.
    Innards inspected. And inspected again. Nothing looks loose to me.
    V2 & V3... alas, I have no spare valves.
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  • fandangofandango Frets: 2204
    Oh yes, thanks for all your help so far. Very much appreciated.
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  • ICBMICBM Frets: 71952
    fandango said:

    The tank is a stock Ruby a RRVL 2AB1C1BV3. Are they any good? Is this type prone to the problems you mention?
    Yes, they're good. In that case it's less likely to be the problem.

    Does the reverb crash if you shake the tank with the reverb level turned up on the amp? If no, swap the cables at the tank and try again. That will tell you if the problem is in the tank, since both ends won't have failed.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • DJH83004DJH83004 Frets: 196
    Do you have a multi-meter? if so you can measure the DC resistance across the phono/RCA plugs that connect into the amp, this will prove the transducers and the leads. Typically on a Princeton you would be looking for approx. 1-1.5ohms on the reverb input and 200-220 ohms on the reverb output (the actual impedances are quoted at 8/2250 ohms, but ignore those).  .    
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  • dannyboy82dannyboy82 Frets: 147

    I had exactly the same issue with my PRRI, it turned out to be one of the valves. I cant remember exactly which one as I believe the reverb has a send and return spread over two valves. I'm pretty sure it was either v2 or v3 though.

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  • fandangofandango Frets: 2204
    DJH83004 said:
    Do you have a multi-meter? if so you can measure the DC resistance across the phono/RCA plugs that connect into the amp, this will prove the transducers and the leads. Typically on a Princeton you would be looking for approx. 1-1.5ohms on the reverb input and 200-220 ohms on the reverb output (the actual impedances are quoted at 8/2250 ohms, but ignore those).  .    
    @DJH83004 - sometimes my mind just can't follow. It's like that now. I think you are going to have to spell this out for me. Does the amp need to be switched on? Are you saying the resistance is measured between the outer and the inner on a single socket? Or should the resistance be measured between the outer of one socket and the outer of the other socket?

    The leads are fine. I tested those, and continuity is assured.
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  • gringopiggringopig Frets: 2648
    edited July 2020
    .
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  • fandangofandango Frets: 2204
    gringopig said:
    fandango said:
    DJH83004 said:
    Do you have a multi-meter? if so you can measure the DC resistance across the phono/RCA plugs that connect into the amp, this will prove the transducers and the leads. Typically on a Princeton you would be looking for approx. 1-1.5ohms on the reverb input and 200-220 ohms on the reverb output (the actual impedances are quoted at 8/2250 ohms, but ignore those).  .    
    @DJH83004 - sometimes my mind just can't follow. It's like that now. I think you are going to have to spell this out for me. Does the amp need to be switched on? Are you saying the resistance is measured between the outer and the inner on a single socket? Or should the resistance be measured between the outer of one socket and the outer of the other socket?

    The leads are fine. I tested those, and continuity is assured.
    He's asking you to measure the resistance between the inner and outer connections of the cable connecting the tank to the amp whilst the cables are disconnected from the amp but plugged in to the tank. This way you are measuring both the integrity of the cable and the transducer at each of the tank.
    There has to be a transducer at the input and output of the tank and it should be a low resistance between inner and outer conductors at the send or input end and 200-220 Ohms at the return or output. Do this whilst the cables are disconnected from the amplifier but still plugged into the reverb tank.
    If they measure good then it's likely a valve is away.
    Many, many thanks.

    Readings are:

    Out = 224 Ohms
    In = 1.5 Ohms
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  • fandangofandango Frets: 2204
    If it's the valves, then I'm looking for one 12at7 and one 12ax7. Might as well replace both valves related to the reverb circuit.

    What's good? What to avoid?
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  • DJH83004DJH83004 Frets: 196
    I would suggest either JJs or TADs in those positions, the 12AT7 is the reverb driver and half the 12AX7 is the reverb recovery, (the other half being part of the pre-amp circuit feeding the PI). Just my personal preference based on ruggedness and longevity.    
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  • ICBMICBM Frets: 71952
    fandango said:
    If it's the valves, then I'm looking for one 12at7 and one 12ax7. Might as well replace both valves related to the reverb circuit.
    No, just replace the faulty one - if it is a valve. Replacing things without definitely identifying the fault just makes troubleshooting harder if the problem returns.

    NOS Philips is the best easily available 12AT7, and not too expensive. Any good 12AX7 will be fine, there aren’t any special conditions for this position.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • gringopiggringopig Frets: 2648
    edited July 2020
    .
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