Amp crackle static when nothings plugged in.

Discussion in 'Amp Tech Center' started by craig paddock, Jun 4, 2017.

  1. craig paddock

    craig paddock TDPRI Member

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    Howdy folks. I'd greatly appreciate some feedback. I've attached a video to youtube of my amp issue. It's a supro reissue. It's been intermittent for the past 6 months.

    Here's the description from the youtube clip explaining what's going on...



    Can anyone suggest what this amp static might be? I've tried cleaning the pots, and that didn't help. Or maybe it did, but it didn't last long to fix the problem. I don't think it's the tubes... These amp designs would seem problematic if it is just dust getting into the input jacks, but my old bluesbreaker never had this problem and the chassis is mounted the same way where plenty of dust can just ride into the jacks where your lead goes.

    2 things I've noticed on my hunt: it's only in the 2nd channel and it's louder as you turn the single tone knob up. Messing with the speaker jack from the chassis to the speaker itself tends to create momentary lapses of the crackle or it just makes it worse, so I was wondering if it could be a bad speaker lead?

    The amp is one of the 15' supro reissues, so bad caps would be unlikely. But maybe it's possible?? I play a lot. I have nos rca tubes in there from the mid 50's, and a tone tubby (brand new) speaker. If I turn the volume all the way down on channel two, I can just play out of channel 1, but I can still hear a bit of bleedover since input one is designed to link the two channels...(theres some bleed over even with channel 2's volume knob all the way down.)
    Any thoughts are helpful!!!!!
    thx!!!!

    Craig Paddock
    www.craigpaddockmusic.com


    ...if you're still reading, thx so much. I read through about 3 different threads and got a bunch of ideas, but I thought the youtube video was worth some hard evidence and before I pay to take it to a tech, I thought I'd ask yall. plus-more than a few times I've taken an amp of mine to a tech, and voila' the problem is gone. (until i'm back home-then it shows up again.)
     
  2. craig paddock

    craig paddock TDPRI Member

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    Can anyone suggest what this amp static might be? I've tried cleaning the pots, and that didn't help. Or maybe it did, but it didn't last long to fix the problem. I don't think it's the tubes... These amp designs would seem problematic if it is just dust getting into the input jacks, but my old bluesbreaker never had this problem and the chassis is mounted the same way where plenty of dust can just ride into the jacks where your lead goes.

    2 things I've noticed on my hunt: it's only in the 2nd channel and it's louder as you turn the single tone knob up. Messing with the speaker jack from the chassis to the speaker itself tends to create momentary lapses of the crackle or it just makes it worse, so I was wondering if it could be a bad speaker lead?

    The amp is one of the 15' supro reissues, so bad caps would be unlikely. But maybe it's possible?? I play a lot. I have nos rca tubes in there from the mid 50's, and a tone tubby (brand new) speaker. If I turn the volume all the way down on channel two, I can just play out of channel 1, but I can still hear a bit of bleedover since input one is designed to link the two channels...(theres some bleed over even with channel 2's volume knob all the way down.)
    Any thoughts are helpful!!!!!
    thx!!!!
     
  3. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Since the tone knob affects it the noise is coming from up stream. Have you tried replacing the 2nd channel's first preamp tube?

    Try cleaning the tube pins by spraying contact cleaner on the pins and inserting the tubes do this 2 or 3 times.

    How old is the amp? A bad plate load resistor can crackle.
     
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  4. Axis29

    Axis29 Poster Extraordinaire Ad Free Member

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    I have been told, static at idle can be a bad tube. It's the easiest place to start. Especially if they are old tubes... I know, I love my old tubes, but even they fail from time to time.

    In other words, listen to @robrob, he knows of whence he speaks.
     
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  5. BobbyZ

    BobbyZ Doctor of Teleocity

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    It's a reissue so not very old.
    I'd bet on a tube too.

    I usually take a good preamp tube and stick it in one spot at a time to find the bad one. If it's a preamp tube. If not then swap power tubes, after that swap rectifier tube if it has one.
    If you still didn't find it a trip to the tech would be a good idea. But I'm betting it's a tube. (don't really do well betting though)
     
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  6. sonofiam

    sonofiam Tele-Meister

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    Sounds like power tubes going out. Thought it could possibly be something else, it's worse than any amp I've had it happen to, until you pulled the cable and it still did it.
     
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  7. darkwaters

    darkwaters Tele-Afflicted

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    I've had this issue with all my tube amps. Like you, I live near the ocean and the climate plays havoc with electronics. Contact cleaner is my solution ( :) ) for inputs and tube sockets as well as pots, cables and inputs/outputs on pedals. Basically anything electronic where contact is made. Rather than spray directly into an input/output jack, I like to use a QTip. Amazing the black gunk that comes out.

    On a side note, I recently realized that I was getting an unusually large amount of popping and cracking when using one pedal in particular. A few years back, one of the battery leads had snapped off. I had it repaired, but I wonder how good a job the guy did. At any rate, I retired that pedal.
     
    Last edited: Jun 5, 2017
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  8. codamedia

    codamedia Poster Extraordinaire

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    IMO - this is never a good assumption. More times than not, it will be a tube.
    • If volume/tone does not effect the sound, look to the PI tube or power tubes.
    • If volume/tone does effect the sound, look to the preamp tube(s).
    Start by re-seating your tubes, preferably with a shot of contract cleaner while you are at at. If the problem exists, roll a known good tube (of same type) into each position and see if it fixes the problem. You do have a spare don't you?
     
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  9. mherrcat

    mherrcat Tele-Holic

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    +1
     
  10. craig paddock

    craig paddock TDPRI Member

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    Thanks guys!

    Ironically, the only tube in the amp that isn't a nos rca is the channel 2 preamp tube (v2) I left the original eh 12ax7 in it cause I don't use that channel as often and I was being cheap. So, if that's the culprit, then p-poop on Electro harmonix. just kidding...all things break eventually...entropy. but that would be interesting. I'm going to mess with the v2 tube...if it's not that, maybe it is the plate load resistor.

    yeah, it was crazy how much black dust came out of the channel 2 input jack with a cuetip! thx for that tip! I also cleaned the speaker jack. It seamed to help, but a few days later the crackle came back. So, we shall see. Hopefully just the tube and/or dirty tube sockets.
     
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  11. Axis29

    Axis29 Poster Extraordinaire Ad Free Member

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    Don't just check that one tube... Check them all. Even the venerated RCAs go bad eventually!
     
  12. Dismalhead

    Dismalhead Poster Extraordinaire

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    My old Bassman 135 does the same thing. Guess I need to check my tubes too.
     
  13. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    I suggest re-reading rob's post and, as he said, ignoring everything downstream of the tone control. The problem has already been isolated. There's a 90% chance everything downstream from that point is unrelated. Some may make noise - but not *that* noise. They are distracting you from the primary issue.

    I do have one question, though. When you say you "cleaned the pots" - what did you use? It should absolutely not be contact cleaner, which destroys the lubricating film in the pots. Only "cleaner/lubricant" or "potentiometer conditioner" should ever be used on pots. No cleaners or solvents.
     
  14. jtcnj

    jtcnj Tele-Holic

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    Good luck on solving your problem.
    do leaky caps allows DC where it doesnt belong and cause crackles as well?

    Ruh-roh. I have used CRC QD Electronics cleaner on stuff including pots.
    Are they likely doomed?
     
  15. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    Honestly, the pots may be toast. If they are crackling now when you turn them they may have carbon deposits deep enough to permanently damage the element. If you used contact cleaner for some time they may also be corroded. You can try using the right kind of stuff to get lube back on them, but contact cleaner is often a one-way street.

    Turning the pots to remove noise after contact cleaner was used just scrapes deposits off and abrades the element. If there were many deposits that grime is scraped along making it worse - it'll be quieter for a few hours sometimes but then be worse. If the correct cleaner/lube is used turning the pot removes light deposits and flushes them off.

    It's also highly recommended to turn all pots to zero when not in use. If they have contact along the travel, even with lubrication on them carbon deposits can build up. And if contact cleaner was used it's almost inevitable that carbon deposits are there - it's a question of how much.

    Once you have noise that's removed by cleaner (or even cleaner/lube) that goes away when they are sprayed but comes back in a day or so the pots are likely shot.
     
  16. craig paddock

    craig paddock TDPRI Member

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    I have read that while basic contact cleaner is ok in small sprays, the deoxit fader f5 contains lubricant and is the way to go.

    So, I ended up taking it to Jens kruse in Los Angeles cause after I checked all the tubes individually and even swapped the old rca's for all brand new electro harmonicx tubes - the problem only got worse. Once the new tubes were in, I turned on the amp, and bam- things went south. I smelled something burning. The amp still played, but at about 20% of the normal output. He is dissecting it now, but his initial guess is a burnt out resistor or two even. And a pretty much filthy-possibly faulty potentiometer.

    Honestly, at this point I don't know... it's as if installing new tubes only seemed to exacerbate the already malfunctioning part or
    Parts. I'm a bit surprised that an amp made in late 14' has burnt out components. I'm always super careful with my amps. But can't complain too much, when the amps firing properly it is magical. For now, my 54' silvertone 1333 has become the working backup, and no problems there. :)))) the silvertone has been an eye opener- and got it at guitar center Hollywood of all places for 600$. All original!!! It barks like an old woman and makes my big toe stick up in my boot :)
    "Little Richard "
    If you can score one on reverb, I definitely recommend it. It's ten watts, yet breaks up before a vox ac4.. and just has that darker old sound. Not for clean fender guys, but actually I can scoop the mids with a catalinbread pedal and it sounds fender ish. Ok enough ranting... just really stoked about the little guy.

    Will report back once bigger little guy supro goes under for surgery.
     
  17. craig paddock

    craig paddock TDPRI Member

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    Thx fir all the feedback
     
  18. alnicopu

    alnicopu Friend of Leo's

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    First things I thought as well. I've rocked tubes around in the sockets and made that sound when it's intermittent. Usually indication of a poor/dirty/loose pin connection. I had a bad plate load do that when I powered down my old blackface Princeton, too. Usually a preamp issue. Amplitude or transient spike noise, kind of like the pops AM radio presents.
     
  19. puddin

    puddin Tele-Holic

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    Wow!!! I'm glad you posted this.. my supro 1624t reissue is doing the same thing. Replaced the original set of tubes with new. New quad pre-amp gold pin matched, and a set of matched power tubes. My isn't as bad as yours.. but does it from time to time. My always hums with little rice crispy noises in the mix. Also, I get a whistling wind noise sometimes. Its soon to go out of warranty, but i don't want to pay for shipping to sweetwater in fear of damage from the shipper..also if its something minor, sweetwater charges 85.00 an hour. I'm looking for a good amp tech in my area, and have it serviced.
     
  20. craig paddock

    craig paddock TDPRI Member

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    I just ended up getting mine serviced by a local well regarded fellow.

    Leaky caps in the tone stack throwing D.C. Voltages at the pots, the volume pot for channel 1+2 was fried.

    Now fixed. Actually got the call today.
    100$ total
     
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