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Originally Posted by Josikulus
My initial suspicion based on these symptoms is that there is something going in the power supply, maybe the rectifier tube is bad.
If it doesn't work to change the rectifier tube (do you have a compatible one in a different working amp perhaps?) it is probably best to take the amp to a technician.
(you could try to probe the power supply, heater supply, or other measuring points, if you have the saftey knowledge, experience and equipment to work on electronics with 500V).
A relatively simple check is to open the doghouse (a compartment on the tube side of the chassis which looks a bit like a small square baking pan) and visually inspect the filter caps. See if they've leaked or bulged. Don't touch anything under the doghouse (the caps could be charged).
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05-23-2022 06:46 AM
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Originally Posted by orri
I now just checked the filter caps. Seem to be fine.
I don't have a different rectifier tube at hand sadly... so can't really test it I guess.
I think the other checks you mentioned are in a weightclass I shouldn't punch in
But yeah, I guess there's not much left to do, than to bring it to a technician...
Kinda hoped I could just replace some tubes or so, but seems it's gonna be more complex and expensive now.
Thanks for the help
If you have any other ideas they are very welcomeLast edited by Josikulus; 05-23-2022 at 11:47 AM.
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Yes, these caps pass visual inspection.
You could try buy a new rectifier tube and replace it. But if it is a bit of a shot in the dark. A technician can find out whether that's necessary.
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Ok yes, so I will leave that to the technician.
Thank you for the help.
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Sad to see that Fender is still using those cheap Illinois caps.
It saves them around $5-$10.00 per amp.
Charge a little extra for caps that will last 15 years.
Of course they want you to buy a new amp as soon as the warranty expires.
Nothing wrong with PCB boards at all. It is the cheap caps on them.
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Just in case try turning all the knobs for a while. My amp tends to sit unused for long periods and I get some nasty problems with the sound too.
Changed a tube helped with one of those of course. But strangely, after hearing crackling while turning some knobs, decided to turn them for a while (standard routine), helped to clean up the sound overall.
Dunno why that could be the issue - I'm completely ignorant in electricity.. I remember from somewhere that the signal goes through all the knobs even through the unused channel's.
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Sorry if this is repetitive.
I had a similar problem with an Ampeg. Very hard to diagnose, very simple to fix.
It turned out that the RCA connector to the reverb tank had stopped making good contact. It was pushed all the way in, but the little wings had bent inward just a hair too far. 10 seconds with a needle nose pliers and it was fixed. It took a couple of years to figure out what was wrong.
If you have it open trace the tank leads back to the circuit board and wiggle them gently to see if you can reproduce the problem.
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Originally Posted by emanresu
And what you exactly did was, turning the amp on then just going knob by know and turning them 10 times up and down all the way, Or about how many times? just that I roughly know when to expect results
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Originally Posted by rpjazzguitar
Wow! I think you hit the nail on the head. I now opened it again and I think I found something:
That doesn't look good right? It actually IS coming from the reverb driver, just as you said.
You think this might be the problem? How would you fix it? Can I carefully unplug it, try to put the cable back between the "wings" and maybe put a little electrical tape around it, to stabilise it?
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Originally Posted by Josikulus
1. Wiggle the wire to see if it reproduces the crackling. If it does, that's an indication that you're in the vicinity of the problem.
2. Figure out what the connection is supposed to look like. I can't quite understand it from the picture because I can't see the uninsulated part of the wire. But, somehow figure that out and make it happen. Might crimp it first and solder it later. Main thing is not to break something you can't fix. If it's one wire and a receptacle, I would hope that it wouldn't be overly complicated, although, you never know. If it was dirt simple it might not break.
If you need electrical tape, you probably haven't made it good as new. The tape will dry out or fall off or something eventually, so it's better to get a solid mechanical connection with no risk of it making electrical contact with anything but the actual target.
3. Since there's electricity in there someplace and it's invisible, I'd suggest wiggling things with a wooden item like a pencil or a wooden chopstick.
In my Ampeg's case it was the RCA jack to the reverb tank. The tank is completely separate from the amp chassis. It's bolted to the inside of the cabinet. It has a lead going in and one going out, of course, and the input was the one that wasn't making good contact. The RCA jack is that short connector with the little wings that hi-fi's used back in the day.
Somebody on the internet advised me to replace a particular capacitor to solve the problem. This turned out to be dead wrong, but in the process of replacing it I accidently wiggled a nearby wire and heard the problem. When I traced that wire I found that it was the one that led to the reverb tank. The connector was pushed in all the way, but as I mentioned that wasn't enough. The wings needed to be spread appropriately.
Good Luck!
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Rob Robinette has some words on tube amp safety to share
Safety
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Originally Posted by Josikulus
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I looked at the picture again and I can now make sense of it.
Looks like there's a right angle in that wire at the entrance to the connector. Might be fine, might not. The wiggle test is probably definitive.
The wire is routed so that it may be touching another connector. It's insulated, so that shouldn't be a problem electrically. Might be a mechanical stress issue, but that seems unlikely. On the other hand, it looks like there may be enough extra wire there to redo the connection with the wire routed in a more desirable path.
You detach the connector, unsolder it. Use a solder remover tool (like a turkey baster, or ear syringe, but smaller) to clean it out. Strip some insulation from the wire to expose about a half inch of conductor, stick it in, solder it and then crimp the top of the connector around the insulated part of the wire.
If you accidentally cut off too much wire, you just patch in some wire from the broken electronic device collection in your neighbor's garage. You can even buy little rubber like tubes that you thread the wire through and then heat. They shrink to become tight insulation. Maybe there's a better way -- my info is decades old. You can use electrical tape but it will eventually offend your aesthetic sense.Last edited by rpjazzguitar; 05-24-2022 at 12:02 PM.
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Originally Posted by rpjazzguitar
Thank you so much for taking the time to analyse my amp's problem and writing these detailed instructions.
Even though my curious mind would really like try this out, I think the risk is starting to get too high with my humble level of expertise and experience. Healthwise and financially...
I would rather invest those 1500$ in new Baum Guitar than in an amp I already paid for, before I put it up in flames
I found a guy pretty close to my home who is supposed to be a guitar amp wizard. So I will bring it to him, see how he does it and learn from him. So next time I will maybe be able to do it alone.
I'm very curious to see what the actual source of the problem is and how he will fix it.
I will post the lessons here once I have them
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If you've never worked on an amp I'd highly recommend against diving headfirst. I like to fix things myself and can service my amps, it's not rocket science but one mistake might be the 1st and last. Poking around w a chopstick is pretty safe and can reveal many common problems but be careful. I'm a pro guitarist and except for minor stuff I leave amp service to the pros, for me life is too short to chance on a little money.
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Coming in late here, so sorry if it's already been suggested, but various caps, not just power supply caps, also coupling and bypass caps and others, can make strange noises as they fail. Often just swapping out tubes isn't enough. I do fix valve (tube) gear, as well as build some, and have experienced this more than once.
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Originally Posted by Josikulus
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I’ve lot’s of experience with audio amps. But when it comes to repairing one I’d rather pay a pro for that’s his expertise.
Has anyone played or had a Supro Amulet ?
Today, 04:44 AM in Guitar, Amps & Gizmos