A tube amp ought not to do this.

[Little Pigbacon]

And you know it’s the Marshall, because of course it is. It’s a JVM410H that’s about eleven years old.

A couple of weeks ago I warmed it up, and when I took it out of standby, it started popping through the speakers. Not super loud, but loud enough to get my attention. Eventually it stopped, I played for a while, then I put it in standby, then off, and cool-down.

Nothing else until one day this week, when it suddenly started making sounds like rustling leaves, or a noisy pot on a live guitar. It eventually quited down; I resumed playing; and it’s been fine the few times I’ve played since then.

It was checked out and biased by a technician about a year ago, and the tubes might have thirty hours on them, if that.

 

[Boogie Bill]

Re: A tube amp ought not to do this.

Just because a tube is new or low hours does mean it isn't bad, motorboating, or microphonic.

Bill

 

[Little Pigbacon]

Re: A tube amp ought not to do this.

The last power tubes had one red-plate at about ten hours. Are tubes just junk now?

Any idea on how to troubleshoot something crazy intermittent like this? I could try replacing one or more tubes, but it could temporarily straighten up on its own in the time it takes me to do that.

 

[Gtrjunior]

Re: A tube amp ought not to do this.

Those are signs that your tubes are going. Just change and bias.
What tubes are you using?

 

[Little Pigbacon]

Re: A tube amp ought not to do this.

JJ EL34. I think I’m ready to try something else.

 

[GoldenVulture]

Re: A tube amp ought not to do this.

Plus ten years old: I'd investigate the power filter caps.

 

[Little Pigbacon]

Re: A tube amp ought not to do this.

Yeah, there’s that.

 

[Gtrjunior]

Re: A tube amp ought not to do this.

I’ve used the Ruby BSTR in my JVM (when I had it). I liked them a lot. My Blackstar came stock with them and they sound great there too.
In my Quickrod I prefer the Chinese Sino from Tubedepot.com. I tried several different brands in the Splawn and the Chinese imo are the best for the job. Plus the price is right.

It’s probably worth having your tech check the filter caps but I’d be willing to bet they are fine. Usually you’ll see some swelling in the caps when they are spent.

 

[dystrust]

Re: A tube amp ought not to do this.

JJ EL34. I think I’m ready to try something else.

Those are supposed to be pretty good in terms of reliability. What do you have in the preamp? It's possible that a failing CF or PI could cause similar noise issues.

 

[LLL]

Re: A tube amp ought not to do this.

The last power tubes had one red-plate at about ten hours. Are tubes just junk now?

What does your experience with new-manufacturer tubes tell you? :13:

 

[IM4Tone]

Re: A tube amp ought not to do this.

Perhaps the sockets and tube pins need Deoxit?

 

[Gtrjunior]

Re: A tube amp ought not to do this.

What does your experience with new-manufacturer tubes tell you? :13:

I’ve used plenty of new production tubes over the years and I’ve had nothing but good luck with them.
Never had one red plate or fail in less than a years time.
I typically change tube yearly when I’m in a gigging band but still, good luck.

I do remember several years ago JJ had a reliability issue going on but they fixed those issues afaik.

 

[Gtrjunior]

Re: A tube amp ought not to do this.

Perhaps the sockets and tube pins need Deoxit?

Yup....first step in troubleshooting. Clean those sockets.
I always clean them with a tube change as well.

 

[dystrust]

Re: A tube amp ought not to do this.

I’ve used plenty of new production tubes over the years and I’ve had nothing but good luck with them.
Never had one red plate or fail in less than a years time.
I typically change tube yearly when I’m in a gigging band but still, good luck.

I do remember several years ago JJ had a reliability issue going on but they fixed those issues afaik.

The exception I can think of is using certain New Sensor tubes in the cathode follower slot, but to be fair they tell you not to do that on their website. I only wish someone had told me before I managed to kill a few of them. :lol:

 

[Gtrjunior]

Re: A tube amp ought not to do this.

The exception I can think of is using certain New Sensor tubes in the cathode follower slot, but to be fair they tell you not to do that on their website. I only wish someone had told me before I managed to kill a few of them. :lol:

Yes...you’re absolutely correct. I learned that the hard way when I had my JVM. Lol

 

[Little Pigbacon]

Re: A tube amp ought not to do this.

Perhaps the sockets and tube pins need Deoxit?

I carefully applied a zero-residue contact cleaner to the pins on all tubes when I changed them last.

 

[GoldenVulture]

Re: A tube amp ought not to do this.

I carefully applied a zero-residue contact cleaner to the pins on all tubes when I changed them last.

Which was how long ago ? Do you live in a humid climate ? Oxidisation on the pins can build up pretty quickly in a humid envoironment.

 

[Little Pigbacon]

Re: A tube amp ought not to do this.

Which was how long ago ? Do you live in a humid climate ? Oxidisation on the pins can build up pretty quickly in a humid envoironment.

About a year ago. It’s not especially humid here. Winters are dry, and we run air conditioning the rest of the year.

 

[Darg1911]

Re: A tube amp ought not to do this.

Try pulling and re-inserting each of the tubes a few times for cleaning. I don't like Deoxit (D5) in tube sockets. It leaves a residue that can attract dust. But then again, our house is a dust factory. Contact cleaner that leaves no residue is fine. But pulling and reinserting the tubes really works well for cleaning the sockets and pins.

When the noise is occurring, if you can get to the tubes in time, you can tap on and/or wiggle the tubes and see which one, if any, is causing the problem. You can also try to duplicate the problem when it's not occurring by doing the same thing. Obviously, wear a glove if they are hot. If you find the problem tube, swap it for a known good spare. If the spare does the same thing, it could be the socket or a solder joint or component at the socket. Noises like you describe, if they are tube related, are usually preamp tubes. At least that's been my experience anyway. But I'm just a weekend hack, not a tech. Tubes are easiest things to rule out first. It could be something more serious, but start with the tubes.

 

[Gtrjunior]

Re: A tube amp ought not to do this.

Try pulling and re-inserting each of the tubes a few times for cleaning. I don't like Deoxit (D5) in tube sockets. It leaves a residue that can attract dust. But then again, our house is a dust factory. Contact cleaner that leaves no residue is fine. But pulling and reinserting the tubes really works well for cleaning the sockets and pins.

When the noise is occurring, if you can get to the tubes in time, you can tap on and/or wiggle the tubes and see which one, if any, is causing the problem. You can also try to duplicate the problem when it's not occurring by doing the same thing. Obviously, wear a glove if they are hot. If you find the problem tube, swap it for a known good spare. If the spare does the same thing, it could be the socket or a solder joint or component at the socket. Noises like you describe, if they are tube related, are usually preamp tubes. At least that's been my experience anyway. But I'm just a weekend hack, not a tech. Tubes are easiest things to rule out first. It could be something more serious, but start with the tubes.

Funny, in my experience the poping noises described have always been power tube issues along with volume fluctuations.