Fender Twin Suddenly Lost Volume Revisited
Question:
Hello all, Thanks for your input before. I have taken the amp to my tech, and the worst possible thing that could have happened has occurred – it plays fine now! So you know what’s going to happen now – I’m going to go pick it up, take it to the gig Friday night – and what’s going to happen – well, what’s going to happen is I’m going to bring two amps with me 
, but, I bet I’ll have a problem again. Intermittent problems are the absolute worst – especially when they can’t be duplicated on the test bench. Just to list the concerns again, in case anyone has any ideas: The amp suddenly went quiet. This occurred when I changed the cable from the Vibrato Channel 1 input to the Normal Channel 1 input. It was fine on VC1 initially – when I switched it, there was no sound. Moving it back to VC1 (and having changed nothing on that channel) still nothing. There was a small pop as I removed the cable from the Normal Channel the first time (like when you touch the end of the cable when it’s plugged into the amp, but not the guitar, but not quite so loud comparatively). I swapped all 4 or the power amp tubes and that did not rectify the problem. I also eliminated any problems with the Guitar or cable and other extra equipment. Now my tech says it’s working "perfectly". Maddening! Thanks for any advice, Steve
Response:
– Hide quoted text — Show quoted text -> Hello all, > Thanks for your input before. > I have taken the amp to my tech, and the worst possible thing that could > have happened has occurred – it plays fine now! > So you know what’s going to happen now – I’m going to go pick it up, take it > to the gig Friday night – and what’s going to happen – well, what’s going to > happen is I’m going to bring two amps with me , but, I bet I’ll have a > problem again. > Intermittent problems are the absolute worst – especially when they can’t be > duplicated on the test bench. > Just to list the concerns again, in case anyone has any ideas: > The amp suddenly went quiet. This occurred when I changed the cable from the > Vibrato Channel 1 input to the Normal Channel 1 input. It was fine on VC1 > initially – when I switched it, there was no sound. Moving it back to VC1 > (and having changed nothing on that channel) still nothing. > There was a small pop as I removed the cable from the Normal Channel the > first time (like when you touch the end of the cable when it’s plugged into > the amp, but not the guitar, but not quite so loud comparatively). > I swapped all 4 or the power amp tubes and that did not rectify the problem. > I also eliminated any problems with the Guitar or cable and other extra > equipment. > Now my tech says it’s working "perfectly". > Maddening!
And it will work perfectly until it screws up again. That may be a couple of hours or maybe a couple of weeks. Then again, it may never happen again. I’ve had a few of these on my bench which did the same thing. On the bench, it’s perfect, put it back in the cabinet and it eventually fails. In the instances I looked at, there’s an internal connector which plugs into nearly the center of the main circuit board, carrying the DC supply to early amp stages. When it works, it works, however the conductors coming out of the connectors make a sharp 90 degree bend as they leave the connector. Still, OK, but when you put this back in the cabinet, the wire bundle gets compressed, putting stress on the solder connections for the connector pins. These eventually weaken and become intermittent. I wouldn’t be surprised if this was the source of your woes. With your amp on in operating position (reverb OFF), if you pound the top of the amp with your fist (a valid troubleshooting technique), do you get a healthy pop and crackle (in the amp, not your hand)? If so, then there’s a connection issue. Whether or not it’s the specific connection I mentioned, who knows, but something on this order is likely. –Mike Mike Schway | [Picture your favorite quote here]
Response:
- Hide quoted text — Show quoted text – > Hello all, > Thanks for your input before. > I have taken the amp to my tech, and the worst possible thing that could > have happened has occurred – it plays fine now! > So you know what’s going to happen now – I’m going to go pick it up, take it > to the gig Friday night – and what’s going to happen – well, what’s going to > happen is I’m going to bring two amps with me , but, I bet I’ll have a > problem again. > Intermittent problems are the absolute worst – especially when they can’t be > duplicated on the test bench. > Just to list the concerns again, in case anyone has any ideas: > The amp suddenly went quiet. This occurred when I changed the cable from the > Vibrato Channel 1 input to the Normal Channel 1 input. It was fine on VC1 > initially – when I switched it, there was no sound. Moving it back to VC1 > (and having changed nothing on that channel) still nothing. > There was a small pop as I removed the cable from the Normal Channel the > first time (like when you touch the end of the cable when it’s plugged into > the amp, but not the guitar, but not quite so loud comparatively). > I swapped all 4 or the power amp tubes and that did not rectify the problem. > I also eliminated any problems with the Guitar or cable and other extra > equipment. > Now my tech says it’s working "perfectly". > Maddening! > Thanks for any advice, > Steve
Sounds like something "mechanical" not "electrical". I’d check the jacks for tension and clean the shorting contacts, also clean the pots, and check for a cold or crystallized solder joint somewhere near the jacks by tapping on joints with an eraser pencil, or cracked input resistor that goes open (maybe tap those with an eraser too). If you know it happened the moment you switched jacks, that spells mecahanical problem to me at least.
Response:
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