Peavey 5150 intermittent problem.

[Erich]

Hi. New to the forum and I hope I'm not breaking any rules. I searched and didn't find an answer to my question.

Anyway, here goes. I've been playing through a solid state Crate combo for years and I've always wanted a Peavey 5150 but only recently was I able to seriously start looking for one, so I found one on Craigslist that had a low enough price that my wife gave me the go-ahead. I went and plugged into it and it played fine, except the guy had a guitar cable with one of the plugs kind of damaged. At one point during the demo the amp signal dropped and came up with a weird swelling static noise, but when we switched the instrument cable around it cleared up, so I didn't think anything of it. I bought the amp. ($800 for the head and an Ampeg cabinet). The guy says it's got brand new tubes in it, but who knows if that's true? I certainly don't know what to look for, except for the little I've read online, and the four power tubes are all fresh and clean-looking and glowing the proper yellowish orange color.

So I took it home and started jamming and it was great... at first. Then it did the thing again. A big chunk of the signal dropped out, mostly low-end, and it started wooshing and swelling. At times it almost sounded like I playing through reverb, almost like what I was playing affected the noise, but if I stopped playing altogether, it would continue. Up and down swelling wooshing sound that sounds kind of like the ocean. The first time it happened, I light clap with my hand on the top of the amp cut it out immediately, but then it started again a little while later and no amount of bopping it upside the head made any difference. Naturally I started to panic and got online and checked a couple of websites and (mind you, this my first tube amp and I know NOTHING) found that it was more likely a problem with my preamp tubes than my power tubes and that you can sometimes troubleshoot by rearranging the order of the preamp tubes. So I did that... switched the first and fifth preamp tubes and that solved the problem for about a day. It played great for a long time, but then the next day it came back, only this time instead of losing the low-end part of the signal, it seemed to lose a whole lot of gain and volume... plus the wooshing sound was back. So I turned it off and registered here. But then just before typing this, I went out to try it out again and it sounds fine again.

So that's where I'm at right now. I left a voicemail with the guy I bought it from but I'd honestly be surprised if I heard back from him. He's free and clear and I can't imagine I can pursue any kind of action toward getting my money back. I guess my big question here is whether or not I should fork out the cash for a new set of tubes or just take it right to the shop. The tubes LOOK new to me. There don't seem to be any blackened or charred parts and they all look like they're glowing the right color, but then again rearranging them did have an immediate, albeit temporary, effect.

Has anyone seen this problem before? Does anyone have any idea what it could be? Am I looking at just needing to replace the tubes or is the amp just garbage?

[g1]

Please read the sticky post about switching jacks at the top of the maintenance page. It is the quickest easiest thing to try, and accounts for a large percentage of problems like this.

[Erich]

Thank you. I had actually just noticed that thread and was reading through it. Thanks! I'll report back when I've tried it.

[Chuck H]

Yupper. Being as the problem was solved temporarily by smaking the amp (an Enzo approved method for troubleshooting) I would guess that your problem is an oxidized contact. A dirty jack, switch, pot, tube pin contact or ribbon cable pin contact. Another possibility is that a cold solder joint is showing itself with age. Cleaning fixes the former. Poking around the board with a chopstick can find the latter and a little hot solder can fix it.

[Erich]

Okay, so as of the last time I posted it sounded fine, and for the most part it never really slipped back into problem-mode. I did go get some contact cleaner at a music shop today, and while I was there discussed my problems with their amp tech. He repeated something I've seen mentioned online a lot; tapping the preamp tubes with a pencil or something and seeing if it produces a noise through the speakers. So I went home and sprayed cleaner into the two effects loop jacks, plus the footswitch and preamp-out jack... and in-and-out'ed a plug into all of them several times while still wet. I plugged in and played for a while but it's hard to tell if it had an effect since the amp was playing fine last time I'd plugged in. All I know is that it continued to play fine.

BUT... then I opened up the preamp hatch in the back and started tapping on tubes, and found that not only did two or three of them react audibly, but (at least) one also got the swelling swooshing ocean sound going again. So then I shut the amp down and pulled all of the preamp tubes out and squirted a little cleaner in the sockets. Let it sit a while and dabbed a dry rag over everything, and plugged back in. The amp is playing fine, ocean sound is gone again... but now only one of the preamp tubes is responding to the tapping, and that is only a tapping sound through the speaker, pretty much just like I hooked a microphone up to the amp and started tapping it. No ocean sound or static or popping or anything.

So now I'm gradually working up the nerve to try to convince the wife to let me buy a set of preamp tubes.

[Chuck H]

Most preamp tubes will make a small ping, tick or thud if you tap them with something. A thud is of most concearn. I might replace a tube if it thuds (funny word). Otherwise, as long as the amp isn't squealing at high gain settings it should be fine.

[Erich]

Most preamp tubes will make a small ping, tick or thud if you tap them with something. A thud is of most concearn. I might replace a tube if it thuds (funny word). Otherwise, as long as the amp isn't squealing at high gain settings it should be fine.

Is your thinking, then, that cleaning out the preamp tube sockets may have done the trick?

[Chuck H]

Yes. But it may be too soon to tell. I've heard that wooshing sound in preamp tubes that were going bad as well as grimy contacts. But I was also saying that if any of your preamp tubes are still making what I can only describe as a "long thud" then you probably should replace that tube. A ping, tick or tock is fine. But a "pffft" sound is grossley loose innards. And that could cause your problem.

[Erich]

Oh. Well... it's hard to describe the sound this tube's making, other than to say it's just amplifying the actual sound of the tapping and sending it through the amp. Before I cleaned the sockets they were more like an electronic thudding, not quite a popping, but more like a very short but loud burst of BUZZ. The sort of sound you might get plugging a guitar into an amp that's turned on already. But now that's gone and it's actually a glassy knock/clink sound. And it's only one tube. The others make no sound at all, but the amp seems to be playing fine.

Also, if it means anything, four of the preamp tubes say Mesa on them, and one says Russian and has some sort of gray plastic or rubber coating around much of the glass. That tube isn't the one that's acting different than the others though.

Either way, I've decided to replace the whole lot. I've been looking around for the tubes I want to buy and I think I've homed in on some JJ's from tubestore.com, mostly because of the price and because I've heard them mentioned a lot as pretty standard or even preferred tubes for this amp. They offer a "matched sections" service for an extra five bucks. How important is something like that?

[Chuck H]

Well it sounds to me like your preamp tubes are fine. So hang on to them when you plug the JJ's in. JJ's are sometimes noisy. I've heard them hissy, hummy and both at the same time to a greater or lesser degree. You may be glad you have the old tubes before long. Also, mark the one that is currently in the first preamp position. That way, if none of the JJ tubes is non microphonic enough to use in the first position you'll be able to ID the old one that you know works.

[Erich]

Yeah, sorry, I'm catching on now. I think I'll give it some time and some drives around the block to see if any of my various small efforts have fixed the problem, since it seems to be acting okay now. It's the pessimist in me insisting that it can't be some small and simple fix. It has to be something major and expensive. But yeah, you're right. All the tubes are now behaving like healthy tubes and the amp sounds good, so it's best to just sit back and see where we're at.

Anyway, we have two shows this weekend and I don't think anything's gonna make me feel safe enough depending on this amp before then, but I'll take it to practice tomorrow. If it makes it through a three-hour practice without any issues, I'll feel a lot better. Two or three more practices like that and I'll probably feel good enough to take it out and put it on a stage.

Oh, by the way... the amp didn't come with a pedal so I ordered a 6505 pedal, since I couldn't get any of the ones I have laying around (Fender and Crate) to do the job. I've seen aftermarket switches advertised as working for both the 5150 and the 6505, which tells me that either original pedal should work for either amp... right?

[Chuck H]

I can't say for certain on the footswitch. But I've read that the two are virtually the same amp, so.?.

I used to hate playing shows without a backup. I had a pair of Marshalls that were very reliable. But on two occasions one was down for awhile and I had just the one amp. I always had my emergency kit with spare tubes, batteries, cables and even a cheap soldering iron. Today it's not so scary. You can get a POD or Sansamp and even finish a gig through the PA if you must.

[Enzo]

The 5150 and the 6505 are EXACTLY the same amp, they just had to change the name when their agreement with Eddie Van Halen expired. The 5150-II became the 6505+. No electrical differences.

[Erich]

The 5150 and the 6505 are EXACTLY the same amp, they just had to change the name when their agreement with Eddie Van Halen expired. The 5150-II became the 6505+. No electrical differences.

That's good to know. I was warned by someone to stay away from both of the 6505's because "they sound like buzz-saws", but I guess that was a case of someone maybe listening a little too hard. Either way, it's a relief because my 6505 footswitch is due to be delivered tomorrow.

Also... I'm pleased to announce that the amp made it the whole way through band band practice, and an extra half-hour of general jamming beforehand, with no issues at all in terms of weird signal loss or background noise or other general malfunctioning. It hisses and hums a little bit, but no more than I would expect from an amp like this. I was, however, a little disappointed to find that it didn't sound nearly as "big" in the bandroom with the band playing along as it did in my kitchen. My bassist isn't a low-lows kind of guy and I think he likes to keep his bottom end right around the same place as mine so he's cancelling out my "balls" a bit, I think, because riffing around between songs still sounded pretty fairly big, but still not quite as big as I was hoping for. Maybe I need to think about speakers or a different cabinet.

Anyway, thanks for the help, guys. It looks like it was dirty preamp tube-sockets after all. I'll report back and let you know of any developments.

[Chuck H]

Turn up the mids. More mids is a guitar players best friend in the mix.