How do I check the tubes in my Peavey Classic 50 amp?

BeatTellender

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It's been making crackling noises lately, tones sound ear bleeding, and I figured it must be the tubes. So anyone can help me with the problem?
 

tubedude

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It's been making crackling noises lately, tones sound ear bleeding, and I figured it must be the tubes. So anyone can help me with the problem?
Do you have any experience with electronics?
If so, remove the tubes and clean/retention the tube sockets and check the condition of the power filter and cathode caps. If not, take it to a tech.
 

Dacious

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When you say tones sound ear bleeding, do you mean like feedback, screeching?

Your amp has four EL84 power tubes. You can try pulling each preamp and poweramp tube out of it's socket, carefully wiping the pins with a rag or cloth with some electronic cleaner or alcohol on the pins. Reinsert it and work it in and out several times. Over time a little tarnish or dust can build up on the connection causing this crackling.

If that doesn't work, observe the power tubes with rear cover off. If the power tubes are very old they could be arcing. If so they need replacing. If the amp is 90s it might need grid resistors as well as tubes, and bias checked. That's a tech to job.
 

BeatTellender

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Do you have any experience with electronics?
If so, remove the tubes and clean/retention the tube sockets and check the condition of the power filter and cathode caps. If not, take it to a tech.
No, sadly I don't. The thing is I don't know where to find a tech. Will Guitar Center work?
When you say tones sound ear bleeding, do you mean like feedback, screeching?

Your amp has four EL84 power tubes. You can try pulling each preamp and poweramp tube out of it's socket, carefully wiping the pins with a rag or cloth with some electronic cleaner or alcohol on the pins. Reinsert it and work it in and out several times. Over time a little tarnish or dust can build up on the connection causing this crackling.

If that doesn't work, observe the power tubes with rear cover off. If the power tubes are very old they could be arcing. If so they need replacing. If the amp is 90s it might need grid resistors as well as tubes, and bias checked. That's a tech to job.
It's definitely a screeching noise whenever I play a chord and certainly doesn't matter what string it is. Where are the pins located? Is it on the tube itself? Today I'm going to buy the electronic cleaner. Hopefully Walmart sells it.

Thank you guys for your help, it's really appreciated!
 

MuddyWolf

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El84s don't last very long. 6months or a year if you play alot. Especially in a combo. Learn what kind of bias method your amp has so you can replace tubes by yourself or you will be spending twice as much money. It's not hard on most el84 amps, some are self biasing.
If you leave bad power tubes in too long you can blow your transformer.
If you go to guitar center, ask what tech they might recommend. Don't just drop off the amp. Or put an ad on CL asking for recommendations.
 

Wally

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The PV classic 50 is a fixed bias amp. When installing power tubes, it is advisable to check the bias. The bias circuit is non-adjustable. There are distributors who can advise what ‘grade’ of tube for that amp.
The United States is a large place…and there are a lot of techs. (;^) Can you narrow the location down a bit so that perhaps a member might make a suggestion in finding a tech.
 

BeatTellender

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The PV classic 50 is a fixed bias amp. When installing power tubes, it is advisable to check the bias. The bias circuit is non-adjustable. There are distributors who can advise what ‘grade’ of tube for that amp.
The United States is a large place…and there are a lot of techs. (;^) Can you narrow the location down a bit so that perhaps a member might make a suggestion in finding a tech.
I live in Homestead, FL, so anywhere around the Miami area or Florida City area would be fine. How do I get a hold of these distributors? How do I check the bias of the amp? Many thanks in advance.
 

Dacious

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One step at a time.

Ok, ringing or feedback means a tube has gone microphonic. You have two sets of tubes in the amp. Small preamp tubes of which one or more usually has a cover. Then the four longer power tubes usually visible through the cooling grill in the back cover

With the amp on and s guitar cable plugged in with volume up, take a pencil or chopstick and tap each tube. You will have to take the rear cover off. Don't touch anything inside the metal chassis especially when it's powered on. If one of the preamp tubes rings, you can replace just that tube. Most guitar stores carry single tubes. Preamp tubes do not need biasing. Unless your new tube is DOA or faulty which is very rare it'll just work. You can do this yourself.



To clean pins it's best to get the cleaner with no lube - Mouser or electronics stores have them. A cotton wool bud works well to clean them. Notice the gap in the tube pins - align them carefully when pushing the tube back in..

If one or more of the power amp tubes rings, especially if the tubes are old, it'd be wise to replace them with a new matched set. Matching involves running then in a special test machine under load to ensure they all operate at a similar spec and draw equal current and respond equally to the signal being presented inside your amp.

It would be wise if your amp is older than a couple years to get a tech to install the power tubes - he can measure things like the volts and current the new tubes draw to make sure they're operating in the correct range for sound and not going to cause problems by drawing too much current and that there's no fault in your amp - then replace or adjust any bad or wandered components. For experienced people this is a regular job.

Its like anything else that converts electricity, produces heat and does require an occasional bit of maintenance. At the same time pots can be lubed, jacks cleaned and tightened

A guitar store should be able to recommend someone. Or there'll be vintage radio or antique audio guys who can do this usually a Google search or yellow pages gives them up.
 
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BeatTellender

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One step at a time.

Ok, ringing or feedback means a tube has gone microphonic. You have two sets of tubes in the amp. Small preamp tubes of which one or more usually has a cover. Then the four longer power tubes usually visible through the cooling grill in the back cover

With the amp on and s guitar cable plugged in with volume up, take a pencil or chopstick and tap each tube. You will have to take the rear cover off. Don't touch anything inside the metal chassis especially when it's powered on. If one of the preamp tubes rings, you can replace just that tube. Most guitar stores carry single tubes. Preamp tubes do not need biasing. Unless your new tube is DOA or faulty which is very rare it'll just work. You can do this yourself.



To clean pins it's best to get the cleaner with no lube - Mouser or electronics stores have them. A cotton wool bud works well to clean them. Notice the gap in the tube pins - align them carefully when pushing the tube back in..

If one or more of the power amp tubes rings, especially if the tubes are old, it'd be wise to replace them with a new matched set. Matching involves running then in a special test machine under load to ensure they all operate at a similar spec and draw equal current and respond equally to the signal being presented inside your amp.

It would be wise if your amp is older than a couple years to get a tech to install the power tubes - he can measure things like the volts and current the new tubes draw to make sure they're operating in the correct range for sound and not going to cause problems by drawing too much current and that there's no fault in your amp - then replace or adjust any bad or wandered components. For experienced people this is a regular job.

Its like anything else that converts electricity, produces heat and does require an occasional bit of maintenance. At the same time pots can be lubed, jacks cleaned and tightened

A guitar store should be able to recommend someone. Or there'll be vintage radio or antique audio guys who can do this usually a Google search or yellow pages gives them up.

I wouldn't describe the sound as feedback/ringing but more like screeching/crackling noise (if it isn't the same description that is). But I will definitely test the tubes with your method.

As for the cleaner, I gotta get one without a lube. By lube, you mean lubricant, right? I'll check my Walmart store tonight to see if they have any. Ok, so the pins are located on the tubes themselves.

I'm definitely going to search for those antique audio stores around my area.

Seems like a lot of work to be done but in order to get the amp to sound as good as it was before before these noise issues came up, would be worth the effort!
 

Les H

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No, sadly I don't. The thing is I don't know where to find a tech. Will Guitar Center work?

Calling Guitar Center isn't a bad idea. They have techs they contract their warranty repairs to so maybe they can put you in contact with one. On the Peavey website they have a list of authorized repair centers across the US.

 

PhoenixBill

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Have you eliminated everything else first though? Taken out effects/pedals and gone with different guitar and different instrument cable?
 

Dacious

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I'm definitely going to search for those antique audio stores around my area.

Seems like a lot of work to be done but in order to get the amp to sound as good as it was before before these noise issues came up, would be worth the effort!

You have a tube amp filled with 19th century tech. If it's a 90s PV Classic that's twenty -thirty years of use. I don't have any guitar amps that arent tube - I can diagnose and work on them myself.

If a solid state amp started squealing or crackling it'd probably be landfill.
 

Wally

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I live in Homestead, FL, so anywhere around the Miami area or Florida City area would be fine. How do I get a hold of these distributors? How do I check the bias of the amp? Many thanks in advance.
An internet search brings up some options for you….
 

Vocalion

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When I was a kid, you’d just go over to your local drug store to test your tubes. I wonder what the contents of this tube tester would be worth right now.

EA7F0392-E670-4F20-8736-0492FAF8B7E9.jpeg
 

uriah1

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I use to gently whack them each with my fingernail. Problem is a lot of new production tubes
are on the verge of not great.
So , I go one by one, replacing them.
 

BeatTellender

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Have you eliminated everything else first though? Taken out effects/pedals and gone with different guitar and different instrument cable?
Yes, I have. Even though I only have one guitar, I just got it back from my tech just recently saying everything with the guitar is good. I've also done recordings with it too with an audio interface to make sure of it. I don't have any effect pedals as of now. It clearly is an amp problem.

You have a tube amp filled with 19th century tech. If it's a 90s PV Classic that's twenty -thirty years of use. I don't have any guitar amps that arent tube - I can diagnose and work on them myself.

If a solid state amp started squealing or crackling it'd probably be landfill.
Mine is definitely a post 1992 model since it has an effects loop. The weird thing is when I got it from the pawn shop the owner said, the amp sounded good when the previous owner of the amp tested it out before selling his amp to him. When I bought it I thought sounded pretty good too, but recently it's been making crackling noises, and now it's making screeching noises whenever I play. It is really annoying to play when hearing those screeching noises going on. 😵

When I was a kid, you’d just go over to your local drug store to test your tubes. I wonder what the contents of this tube tester would be worth right now.

View attachment 1016868
These would be pretty good to have for sure.
 

archetype

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When I was a kid, you’d just go over to your local drug store to test your tubes. I wonder what the contents of this tube tester would be worth right now.

View attachment 1016868

The contents will likely be worth very little. A small subset of those tubes would be applicable to guitar and other audio amps. The majority would be radio and TV tubes that have near-zero value. Maintenance of older radios and TVs is the tiniest of niche markets and vendors are over-stuffed with those tubes.
 

PhoenixBill

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Yes, I have thousands of tubes (I bought them in a few large lots) and the vast majority of them are oddball radio/TV tubes. That included a couple of full tube caddies, again almost all were TV tubes. As far as the neighborhood tube tester in the picture: it’s almost worthless as a real testing device. It will detect a shorted tube, or a tube that is practically dead, but that’s the extent of it. Even top-of-the-line testers can’t usually tell if a tube is microphonic. And certain tubes, like the common 12AX7, are difficult to get a reliable reading on with some testers (the operating voltage may be too low, or other test parameters don’t really match the tube). So when I go through unknown tubes, I do use the tester to eliminate those that are shorted or otherwise dead but in some cases it’s putting the tube in use in its intended device that is the real test. Some tubes will work perfectly fine in some applications but the very same tube will be problematic in other places.

TL;DR…tube testers are limited in their capabilities, and most “old” tubes out there are useless TV tubes.
 

PhoenixBill

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By the way, I had a Classic 50 tweed many years ago. It was a good sounding amp, and I kinda regret selling it. However, it had a couple of limitations. To keep the amp affordable, (going from memory) the tube sockets were soldered directly to the printed circuit board (a common practice today, even some expensive amps are like that). If care isn’t taken when removing or inserting tubes, the solder joints at the tube sockets can crack or the board can even break. This is not an amp for a beginner to hone their amp-repair skills on, as removing and reinstalling those boards require care. And since the tubes don’t have much to isolate them from the vibrations of the amp as the amp is played, they did physically “tinkle” on certain notes in my amp. So I can certainly see the preamp tubes going bad from the physical vibration.
 




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