Very harsh popping and crackling noises from Vintage tube amp.

Discussion in 'Amp Tech Center' started by BryanLasalle, Sep 16, 2019.

  1. BryanLasalle

    BryanLasalle TDPRI Member

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    Hey there,

    I'm having trouble with my amp as of recently, it has been acting up a lot within the past month in the way of extremely loud popping and crackling noises even with no volume. It is a 1968 Fender Bassman head paired to a 2x12 4 ohm cabinet and I've been able to play on it just fine until very recently as I stated. I would rather prefer to try and get advice before bringing it in to the repair technician that I go to for a servicing/diagnosis. I have checked and replaced all pre amp and power tubes and they are all fully functioning and every socket is cleaned out. I have sprayed the controls as well to clean them off from any debris or gunk that might have built up. It also pops extremely loudly when tapping the top of the wooden chassis that the amplifier frame is connected to. Sometimes it runs smoothly, and others it's like a wild horse, the noises are extremely harsh and extremely loud and I fear that it might cause damage to the amp itself or cabinet if I don't figure something out. I also feel like the idle static noise you get from vintage amplifiers is a bit louder than usual as well.

    Sorry for the long explanation but I wanted to be as detailed as possible.

    Thanks,

    - Bryan.
     
  2. Bristlehound

    Bristlehound Friend of Leo's

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    Have you tried the 'chop-stick' test on the circuit board? Very carefully use a wooden stick - not a pencil 'cos graphite conducts - and gently tap components and solder joints to see if you can isolate what's causing the problem. You did the first obvious thing in cleaning up the tube sockets. They may need re-tensioning.
     
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  3. VintageSG

    VintageSG Friend of Leo's Ad Free Member

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    Joints that have dried and/or cracked over time can do that. Capacitors can act weird, just to annoy you. Resistors can fail internally in such a manner that they conduct, then go open, then conduct at odd values ( Clay composite types. Film types are rather more stable ) as they age and suffer the ravages of heat cycling.

    Bristlehound has the right of it. Get in there with a chop-stick.
     
  4. Telecastoff1

    Telecastoff1 Tele-Holic Silver Supporter

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    Carefully check the solder joints along the brass rail, just below the row of pots. That area is notorious for broken solder joints on old Fender tubers.
     
  5. 24 track

    24 track Doctor of Teleocity Silver Supporter

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    also check your filter caps , a 60 old amp will have bad caps, they will dry out and act funny, look for any blistering or leakage on the caps , also as mentioned bad soldered conections could be an issue " never put your hands into a live or uncharged amp the residual voltage can/will kill you" use a chopstick to prod around,
    remember the one hand rule: one hand in your pocket when you go in
     
  6. stefanhotrod

    stefanhotrod Tele-Meister

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    Bad caps, cold/broken solder connection?
     
  7. muchxs

    muchxs Doctor of Teleocity

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    Loud "snap, crackle, pop" is your amp begging you to take it in for service.

    It could be any number of things. Tinkering with the amp might add a few more uncertainties.

    WAG time. I'd guess a bad speaker connection. Speaker connections should be soldered. Even if they're soldered, a '68 Bassman is a head. the speaker cable gets yanked every time the amp is moved.

    I worked on an old Fender a while ago that must have been a Friday afternoon amp. '60s Fenders had multiple ground points. I was able to lift most of the grounds with my thumb nail.
     
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  8. Wally

    Wally Telefied Ad Free Member

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    Shut the amp off and take it to a good tech.
     
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  9. schmee

    schmee Poster Extraordinaire

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    If it's a real loud pop or crackle, Check the green filament wires to the tube sockets. Wiggle them with a wooden stick or etc while the amp is on. Often these thick wires in a bad solder glob will do that at the tube socket. There are numerous other possibilities too. Chopsticking the circuit board is good, but often the noisy component won't actually be the culprit, just a related symptom.
     
  10. teleman1

    teleman1 Tele-Holic

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    Before you do anything, do the tap test mentioned prior. Use a Pencil with an eraser end. While the amp is on, low volume setting, and perhaps plagued in. Tap each tube. If you get noise, that tube is probably the culprit,(especially if you have modern production tubes). Listen for your noise.
     
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  11. 57fenderstrat

    57fenderstrat Tele-Meister

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    If it were me I wouldn’t go in there looking for something unless I planned on fixing it myself. I would just take it to someone you trust to do it. Good luck !
     
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  12. Paul G.

    Paul G. Friend of Leo's

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    If you don't know about electronics, and don't understand circuits and have no idea where high (potentially lethal) voltages live, I would just take it to a tech.
     
  13. D'tar

    D'tar Friend of Leo's

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    Please don't use a pencil to chopstick inside an amp. A non conductive plastic or wooden dowel or a........ chopstick, etc.
     
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