Tube amp issues

[Creamer298]

I've had my Peavey Classic 30 since... 2006 or so? I've never needed to do any sort of repairs or parts replacements. However, since ~last September, the amp has been unusable.

 

When I plug it in and turn it on, it warms up and then begins a terrible, loud, muddy NOISE. This happens regardless the volume setting/channel and whether I'm plugged in or not.

 

I don't really know the best way to describe the sound, but it is terrible. And, like I said, it is really loud regardless the volume setting.

 

In January I finally got around to taking it to a local repair man. However, after 2 months he still hadnt even touched it due to a crippling illness. I want to take it somewhere else, but I figured I would check on here to see if anyone had any sort of idea as to what the problem may be.

 

Im really inexperienced with this kind of stuff, but hopefully I can answer any questions you guys have.

 

 

 

 

 

[pinkjimiphoton]

take the power tubes out, and replace them, they're small bottle el84's and need to be replaced about every 3 months or sooner cuz they run HOT.

sounds like a shorted power tube to me. they're cathode biased (close enough) so you can just pop a fresh quartet in. also change the 12a_7 (12at7 or 12ax7) closest to the power tubes, as it's driven really hard as well. preamp tubes aren't a worry so much unless it squeals or gets microphonic.

if ya act quick, the amp may survive....they are pretty forgiving.

 

if the problem doesn't go away with fresh tubes, suspect a bad filter cap in the power supply if the amp is motorboating (put put put bass sound) or just oscillating a bass frequency.

 

if you're lucky, it's a bad tube...replace 'em and you should be good to go, and remember in the future to change them frequently. good luck, mate..

[Creamer298]

Thanks for the response!

 

Unfortunately, I've never done any sort of electronics work with my amp... The most work I've ever done is solder a part on my old Dean Evo.

 

I'm at home for lunch right now and I'm looking at the amp, and I see the el84 tubes as well as the 12ax7 tubes. They are clearly labeled.

 

Would you care to briefly walk me through the process of replacing the tubes? Like I said, I've never done anything like this before.

 

May be a stupid question, but is there any danger of electric shock? Obviously the amp would be unplugged.

 

Thanks!!

[pinkjimiphoton]

take the amp, turn it on, then unplug it with the standy switch in the on position. let it set for a couple minutes.

 

unscrew the metal guard over the el84's if it has one.

pull out one tube at a time.

 

they're keyed, will only go in one way. be gentle, them bottles can crack easily.

 

put the new tube in.

 

repeat 3 more times.

 

turn off the amp power and standby, and plug it in the wall.

turn the power on, let it warm up on standby for a minute or so.

 

hit the standby...if the amp sounds good again, problem solved.

 

if it starts f'n up, turn off immediately, and take it to a good tech. if you're not reasonably familiar with high voltage electronics, messing around can seriously hurt...or kill...you.

 

good luck man...hollah back, got my fingers crosseder than my eyeballs are...

[Creamer298]

Well, that's awful reassuring!!

 

My Classic 30 doesn't have a "Standby" it is just on or off, as far as I know.

 

Any tips to avoid getting zapped? I'd very much like to not get zapped.

[russclan]

If you're just going to try replacing the tubes yourself, there's no chance of getting zapped...the procedure is an expected necessity as a tube amp owner. Just follow Jimi's instructions - it's easy.

 

Don't open the chassis if you don't know what you're doing. Even when turned off and unplugged, certain components have stored juice. You have to bleed it off if you're going to work on the innards.

 

If replacing the tubes (and you should, if you haven't done it in ~5 years) doesn't solve the problem, take it to a repair tech.

[pinkjimiphoton]

leaving it "on" and unplugged can drain any stored voltage, but seriously, just slap the new tubes in, you won't get hurt. just don't mess around inside the chassis.

[Caevan O’Shite]

With the amp off, FIRST remove the driver/phase-inverter tube (it will be the "preamp-tube" that is located the closest to the output-tubes, usually right next to them, most often a 12AT7 or 12AX7 (ECC83, 7025, etc.); turn on the amp- if the noise has stopped, replace that tube (see below for further recommendations here), and if the noise is still gone, you're done.

 

- If the noise went away when that tube was removed, but immediately returns when you replace that tube, begin checking the preamp-tubes one at a time, in the same off/on removal/replacement/trial-and-error way, to find if a preamp-tube is at fault. Find one where the noise goes away when removed AND replaced? Done.

 

- If the noise does NOT stop when the phase-inverter tube is removed (no tube in that socket, amp on), then remove and substitute/replace the output-tubes as a set (four in your case, right?). Noise goes away and stays away when the output-tubes are replaced? Done.

 

If none of the above tube removal and substitution solves the problem, then it is very likely one of the following:

 

- A bad filter-capacitor (very large electrolytic caps, probably under chassis in a "pan"- considering your inexperience do NOT touch them- literally, don't get in there, take it to a qualified, experienced pro)

 

- Loose component(s) or connection(s)

 

- Loose ground-wire

 

- Bad input-jack or bad connection/solder-joint at or involving the input-jack

 

- Bad resistor

 

All of which, considering your inexperience, would call for a trip to a qualified, experienced pro.

 

 

I will add that if you replace the output-tubes, get a matched set, and in a "#5" or "#6" rating ("Average"). In a cathode-biased amp, you will not need to adjust the bias of the output-tubes, they're essentially "self-biasing", determined by the values of components between the cathodes and ground.

 

 

I will also add that, if you replace the output tubes, always replace the driver/phase-inverter tube along with the output-tubes; and replace it with one that's been tested to be strong AND "balanced" or "matched", that is, its two internal triodes have nearly identical properties- this can make a HUGE difference in overall tone and performance. SERIOUSLY.

 

The reason that I recommend replacing the driver/phase-inverter tube along with the output-tubes is that they work together and wear together as a team. You could always save the old D/P-I tube to use as a spare for another socket in the amp, but mark it with a Sharpy marker (they write on glass and their ink will hold up against the heat) as USED for future reference.

[pinkjimiphoton]

only thing is kev, the amp has NEVER HAD THE POWER TUBES REPLACED. if one of them is shorted...likely with small bottles like 84's...it will smoke the amp with it. i humbly would suggest starting with the quartet of el84's. the preamp tubes blowing won't smoke your output transformer and power supply, and them peaveys are a pain in the .... to work on.

jmo.

[Creamer298]

OK guys thanks for all the responses, sorry for the naivety. Will post back with updates as soon as she's up and running...

 

Where do you guys buy your tubes?

[pinkjimiphoton]

lol,...i don't use tubes anymore, its been years now...i usually buy 'em from a friend that does amp repairs. 84's are cheap, you can get 'em damn near anywhere!

[Caevan O’Shite]

Yeah, I'll buy that, pjp; even if the output-tubes aren't the cause of the noise, it's a safe bet that they need to be replaced by now, for sure. Safer either way. Good call.

 

 

I can highly recommend Doug's Tubes; I used to order from Groove Tubes when Myles Rose worked there, but since he's left GT I took Myles' recommendation of Doug's Tubes and have been very happy with the few purchases I've made. You can tell Doug what amp, guitar, pedals you're using, how you're using them, and what sound you want, and he can help very well with the specific tube-selection for each socket/application and testing/rating details.

[Creamer298]

I removed the first pre-amp tube; no noise. I'll replace it and see if that makes a difference.

 

I'll also look into changing out the whole set of power tubes.

[russclan]

leaving it "on" and unplugged can drain any stored voltage, but seriously, just slap the new tubes in, you won't get hurt. just don't mess around inside the chassis.

 

Yeah, but ya never know, ya know?

[russclan]

lol,...i don't use tubes anymore, its been years now...

 

What are you playing through these days Jimi?

[pinkjimiphoton]

I removed the first pre-amp tube; no noise. I'll replace it and see if that makes a difference.

 

I'll also look into changing out the whole set of power tubes.

 

don't f*** around with the preamp tubes other than the driver.

yank them old el84's out now. get another quartet. if them are the same tubes that were in there when you bought the amp, it WILL blow the amp up. trust me.

my co-guitarist in the easton brothers has blown up FOUR of them things...irreparably (well, expensively, more than the amp was worth)by not changing the power tubes. including the pristine delta blues he just bought a couple weeks ago.

it's not like a 6l6 or something that can survive for decades. the amps are biased close to class a, and run hot to begin with.

you WILL kill the amp, if it's not dead already.

 

the sound you describe is either a roasted power tube, or a filter cap in the power supply getting ready to let go...

you don't need to worry about electrocution just changing the tubes. like, zero chance of injury from the electrocution, just to be clear.

well, maybe not zero, but close.

 

the preamp tubes can last for DECADES. an el84 can last HOURS. if you play it for 3 hours once a week, you should change them every three months or so, max. they don't last very long!!!

i've seen 'em melt, i've seen 'em fail right out of the box even sometimes. if ya dig the amp, don't play 20 questions, just change the power tubes. trust me. it may seem like i'm trying to get ya to spend cake...and i am...preemptively. a quartet of el84's will set ya back about 30 bux (i imagine...haven't used them in years)...a new output transformer, if that's all that cooks, will cost ya close to a c-note...plus repair expense, rebuilding the power supply, etc...spending 30 bux now, and on a regular basis, can save ya a hefty repair bill later. ask myles..i have a feeling he'll tell ya the same thing.

 

 

that said...as for amplification these days, depending on the gig, i use either a behringer v-ampire head thru a 2x12 cab with vintage 30's (if doing power trio/hard rock....people always think it's a marshall, lol...totally digital), an old marshall mosfet 1x12 combo (if i'm REALLY lazy and just wanna have something lite and loud with plenty of baalz), or my rack, which is a marshall 9001 tube preamp, a roland gx700 processor and a ps systems power tool.

but most of the time, depending on the size of the gig, i use a fender cyber twin or cyber deluxe...mostly the deluxe these days.

 

i also have a princeton (pawned at the moment, which is killing me) which is the last tube amp i own...it's an early 80's blackface reissue with the boost knob...i gutted it, stuffed in the ass end of an ampeg, a marshall pre with vox tone stack, and added a couple cathode bypass switches. when all said and done,

it's about 60 watts thru a 12" 100 watt celestion, and is like a mini marshall with reverb, trem, and a footswitchable overdrive. it's pretty sick, as soon as i can drop 300 for it i'll get it back.

 

but these days? not a tube in site usually!

[Larryz]

The cool thing about tube amps is that you can check the tubes and find a problem without taking the amp to the shop 1st... solid states (unless you're a techie or have some electronics training) usually have to go to the shop period...first thing I would do is turn off the amp and unplug it from the wall...then I take the tubes out marking the base with a piece of colored tape or dots and record each tube and socket it came out of...then I take them to my buddy and we check them on his stingy tube checker...if they all test good, then they go back exactly where they came from and the amp goes to the shop...if I find some bad ones, I have probably found my problem...I save the good ones in a box and toss out the bad ones if ordering new tubes...my power tubes are two 6L6s and when ordering new ones I order a matched pair (I use Fender Groove tubes-red)...after replacing the power tubes (if one or both are bad) I have the bias checked and reset as necessary before using the amp (my other buddy does this job for $20 bucks)...

[pinkjimiphoton]

he doesn't need to bias his amp, he can just put new ones in...it's quasi cathode biased, so it's easy. but again, unlike big bottles, them little ones burn up a lot faster than a 6l6 will.

ALWAYS change the whole set of them at a time, if one tube has failed, the others will too in time. tubes are cheap...repairs aren't. peace.

[Caevan O’Shite]

he doesn't need to bias his amp, he can just put new ones in...it's quasi cathode biased, so it's easy. but again, unlike big bottles, them little ones burn up a lot faster than a 6l6 will.

ALWAYS change the whole set of them at a time, if one tube has failed, the others will too in time. tubes are cheap...repairs aren't. peace.

 

EDIT:

This amp- the Peavey Classic 30- IS "fixed-bias", meaning that it is NOT cathode-biased or "auto/self-biasing", but it also does NOT have an adjustable bias-pot, but is biased by select-valued resistors similar to the way many MESA/Boogie amps are.

 

If you get output-tubes from a qualified vendor/tester like Doug's Tubes, you can tell them that they're for a Peavey Classic 30 and they'll be able to select a matched-quartet of them that will match-up well with the amp's pre-set bias.

 

Now, I agree with pjp, even if the output-tubes aren't the direct cause of the noise issue, they need to be replaced, and yours are long overdue; and again, pjp's right, most currently available EL84's are more fragile and less durable than many other types...

 

(In case you misunderstood, pjp meant replacing the whole set of output-tubes (the EL84's) at a time, not necessarily all of the tubes in the amp.)

 

I strongly advise you to also replace the driver/phase-inverter tube along with them, as well, 'cause they work and wear-out together. Go with a good, strong "Matched Phase Inverter" ("MPI"), aka "balanced", too. See Myles Rose in the "Feel free to ask Myles"-thread, and/or Doug at Doug's Tubes for more info and top-notch advice.

[pinkjimiphoton]

kev is 100% on the money. the preamp tubes are most likely fine. the driver is NOT a "preamp" tube, but part of the power amp, and needs to be replaced often as well...not as frequently as the 84's do. you CAN replace it every couple months, it won't hurt anything...as ya get more familiar with the way the amp feels, you'll be able to tell when it's getting weak. safest bet is to replace it with the power tubes...and replace the ENTIRE QUARTET, don't try to get by with changing just one...you're inviting disaster. peace

[Creamer298]

Thanks guys. I'll post back after replacing the power tubes and let you know whether or not I avoided catastrophic damage.

 

This has been a nice learning session, thanks for the knowledge!!

[Larryz]

he doesn't need to bias his amp, he can just put new ones in...it's quasi cathode biased, so it's easy. but again, unlike big bottles, them little ones burn up a lot faster than a 6l6 will.

ALWAYS change the whole set of them at a time, if one tube has failed, the others will too in time. tubes are cheap...repairs aren't. peace.

 

+1 change 'em all at the same time with a matched set...my twin had 4 power tubes, my de ville only has 2, and now I've solved with whole problem with a zt club 12 solid state that only weighs 22lbs...

[pinkjimiphoton]

man, i hope you avoid the catastrophic damage part, cuz that would like, suck a suckload of suck~!

[Caevan O’Shite]

Y'know, I've got a little Carvin 'Vintage 33', a fake-tweed covered 33 watt, 1x12 combo that runs a quartet of EL84's, cathode-biased, "Push-Pull Class-A"; Myles recommended and hand-picked a matched-quartet of GTEL84S's for me that he'd tested himself, and damn if they haven't proven an exception to the general rule and have lasted and lasted and LASTED.

 

The preamp-tubes and "MPI" (driver/phase-inverter) that he also picked for me- including GT's "Marshall High-Gain" kit- have held up admirably, as well, save for some microphonic issues- which, happily, have been greatly and satisfactorily tamed by judicious placement of three "Hal-O" tube-dampers on the first three preamp-tubes, which excellently nixed-out the whistling and ringing.

 

Between 'em, I've gotten waaay more useable life out of 'em than usual, certainly more than I'd expect, thankfully! And I DO push the amp pretty hard...

[pinkjimiphoton]

be careful, if they start getting mushy or microphonic, change 'em quick.

 

note: microphonic POWER TUBES don't squeal like preamp tubes do, they rattle amazingly close to the sound of a blown speaker, and often on notes like 2nd fret f#'s. if ya hear that kind of sound, time to change 'em, too.

[Caevan O’Shite]

be careful, if they start getting mushy or microphonic, change 'em quick.

 

note: microphonic POWER TUBES don't squeal like preamp tubes do, they rattle amazingly close to the sound of a blown speaker, and often on notes like 2nd fret f#'s. if ya hear that kind of sound, time to change 'em, too.

 

Definitely.

[bennyguitfiddle]

i have a 1945 national amp that is doing that very thing.

damn now i am gonna have to drop some bills.

[p90jr]

I've had my Peavey Classic 30 since... 2006 or so? I've never needed to do any sort of repairs or parts replacements. However, since ~last September, the amp has been unusable.

 

When I plug it in and turn it on, it warms up and then begins a terrible, loud, muddy NOISE. This happens regardless the volume setting/channel and whether I'm plugged in or not.

 

I don't really know the best way to describe the sound, but it is terrible. And, like I said, it is really loud regardless the volume setting.

 

In January I finally got around to taking it to a local repair man. However, after 2 months he still hadnt even touched it due to a crippling illness. I want to take it somewhere else, but I figured I would check on here to see if anyone had any sort of idea as to what the problem may be.

 

Im really inexperienced with this kind of stuff, but hopefully I can answer any questions you guys have.

 

 

from what I've heard Peavey are good about customer service. Call them if you can't get it sorted and they might recommend someone...

 

I'm one state over and there's tons of stories here about people just driving over with malfunctioning gear and they fix it at Peavey headquarters. It's like local folklore.

 

I like Classic 50s. Classic 30s and I don't get along for some reason... I make them sound like they're dying a horrible death. Don't know why that is, but some amps and my fingers don't gel, the guy who fixes my amps says I just need a lot of clean headroom in the preamp.

 

Anyway, I was going to buy a Classic 50 a good while ago but he suggested I get a Fender Bassman or DeVille instead, because it would be easier for him when he had to fix them. The Peavey Classics use a printed circuit board and then a lot of chips on top of that, which makes them complicated to work on... and makes them a bit prone to problems if worked a lot from what he said.

 

I got a 4 x 10" DeVille tweed instead and it performed fine for the most part, but there's a printed circuit board problem now with it in the preamp so I've moved on to other amps (all with PCBs, incidentally, with no problems)... it was well used when I got it and I gigged the hell out of it for 10+ years.

[p90jr]

The cool thing about tube amps is that you can check the tubes and find a problem without taking the amp to the shop 1st... solid states (unless you're a techie or have some electronics training) usually have to go to the shop period...first thing I would do is turn off the amp and unplug it from the wall...then I take the tubes out marking the base with a piece of colored tape or dots and record each tube and socket it came out of...then I take them to my buddy and we check them on his stingy tube checker...if they all test good, then they go back exactly where they came from and the amp goes to the shop...if I find some bad ones, I have probably found my problem...I save the good ones in a box and toss out the bad ones if ordering new tubes...my power tubes are two 6L6s and when ordering new ones I order a matched pair (I use Fender Groove tubes-red)...after replacing the power tubes (if one or both are bad) I have the bias checked and reset as necessary before using the amp (my other buddy does this job for $20 bucks)...

 

This is true but I played a solid state amp hard through my teenage/college years and the only problem I ever had was a blown fuse. Ever! It was a '79 Acoustic, i think... and it sounded great, until I stopped playing strats and developed a taste for Gibsons and it didn't. There was an article somewhere recently detailing how solid state amps were received as a big advancement in dependability in the late 60s... especially those by Standell, Sunn, Vox, Acoustic... even Fender and Music Man going for solid state rectifiers or preamp sections were viewed as an advancement. And we all know the Roland Jazz Chorus was King Kong on the skyline for a period.

 

I need tube amps, now... but sometimes my wallet wishes I'd stayed innocent and satisfied with SS.

[Caevan O’Shite]

"...it sounded great, until I stopped playing strats and developed a taste for Gibsons and it didn't."

 

 

"...the Roland Jazz Chorus was King Kong on the skyline for a period?

 

I'm apparently a rarity in that I cannot stand Roland's JC line of amps! However...

 

"I need tube amps, now... but sometimes my wallet wishes I'd stayed innocent and satisfied with SS."

 

Roland's Blues Cube series of SS amps are pretty damn good for SS, and used specimens can be found used for decent deals...