Mystery Problem Involving Tube Amps PLEASE HELP!

[BigDreamer]

So this will be rather long, but I really need help, so stick with me!

Ok, so my band and I started renting a storage facility unit as a rehearsal space a little over a month ago. Everything has been great up until the last couple weeks. My amp, a Mesa Tremoverb, will start out fine for like 15 minutes after turning it on, and then the distortion channel gets extremely farty and just sounds like six fuzz pedals on at once--just awful! And then the clean channel gets really low in output and sounds, well, not clean, highly distorted in fact. (Note: The solid state bass amps, and the PA works fine.)

So I:

Completely retubed all the preamp tubes--didn't fix it.

Completely retubed the power section--didn't fix it.

Checked the fuse--fine.

Tried multiple guitars--same problem with all of them.

Took everything out of the signal chain and tried multiple cables--didn't fix it.

Tried plugging into the surge protector I normally use, and an array of other wall outlets, with nothing but the tube amp plugged in.

Now HERE'S the kicker:

I borrowed my friend's Mesa Rectoverb Combo, plugged it in, and it worked great for about 15 minutes...and then, what do ya know, it does the EXACT same thing, and then got worse! It would power on, but there was no output at all. (Tried all the above debugging on it too, outside of tube changes.)Not only that, but when I brought his amp back to his apartment, it no longer worked properly. It would at least make sound, but it would be unusually low in output on both channels and completely clean--couldn't add any gain.

I've actually even brought a little solid state crate and, while it worked better, it was still iffy...


And now, Kicker #2, brought my tube amp back home, plugged it in, NO PROBLEM at all!

SO, I've narrowed it down to being either shoddy electrical work at the facility or some sort of environmental conditions...I have no idea!

So if anyone could help me:

A: figure out how to be able to use my amp again at the rehearsal space.

B: help me diagnose my friend's amp's problem so I can help him fix it.


Thanks so much for taking the time to read this! Hope someone can help!!!

 

[Tom Huff]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

Get a good power conditioner? SS equipment is more tolerant of bad power. That is such a strange problem man. I wish you luck.
Crap. I hope your friend's OT didn't crap out!

 

[uOpt]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

Get one of those UPS you use for computers. Just a conditioner will not fix it if the power really collapse.

Overall I suspect the story will turn out to be deeper. The power thing sounds unlikely.

The primary symptoms, not counting the cross-tests with the other amp, sound like a bad output transformer to me. Did you use the same cab for your and your friend's amp?

 

[Tom Huff]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

Get one of those UPS you use for computers. Just a conditioner will not fix it if the power really collapse.

Overall I suspect the story will turn out to be deeper. The power thing sounds unlikely.

The primary symptoms, not counting the cross-tests with the other amp, sound like a bad output transformer to me. Did you use the same cab for your and your friend's amp?

Are you suspecting OHM issues? Interesting.

 

[BigDreamer]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

Well my friends amp is a combo, so it should rule out ohm issues.

 

[uOpt]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

I didn't mean speaker impedance. I meant the original problem for the first amp sounded like a broken, but not entirely dead, output transformer to me. Once it's warm it collapses. Could also be the power transformer.

The second amp thing is a little too mysterious to debug over the Internet.

Theoretically bad power could have (temporarily) killed both power transformers. But it is more likely the explanation is something that we just don't see wit the limited data at hand.

Does a PC work on the same outlet?

 

[Surgeon]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

If the amp worked fine at home afterwards I doubt that it could be the OT...

 

[wixedmords]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

Sounds like 2 different things happened to you BigDreamer. Use one of your extra preamp tubes to swap out the preamp tubes in your friends amp. If swapping the preamp tubes doesn't fix it, you will likely be looking at picking up a set of power tubes for your bud's amp. You also may be able to borrow a known good set of power tubes for troubleshooting purposes.

If you have a multimeter you can check the wall voltage at your practice spot. You may be looking at conditioning and power backup.

 

[uOpt]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

If the amp worked fine at home afterwards I doubt that it could be the OT...

If you take all the available data into account there aren't any reasonable explanations left.

 

[J Moose]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

Get one of those UPS you use for computers. Just a conditioner will not fix it if the power really collapse.

UPS isn't always the right answer for music/audio gear... a lot of 'em will inject noise & other interference... so they'll fix one problem and create others. There ARE systems designed for audio equipment but they co$t.

Something like the Furman AR1215 is what you'd need if it IS indeed a problem with low-voltage. The 1215 is a regulator with a massive transformer... takes anything from 95 volts to 140 & spits out an even 120.

First thing you'd need to do is figure out if it actually IS related to power... which it might be. Get an outlet tester & multi-meter from rat shack & see if the outlets are wired properly & what they're putting out.

Most "storage spaces" have fairly sloppy wiring...

Might be easier to find a new place to rehearse.

With your friends amp if the voltage was really low chances are good that it led to cathode stripping in the tubes which would explain quite a bit...

 

[Surgeon]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

If you take all the available data into account there aren't any reasonable explanations left.

I know and I'm probably not as knowledgeable as you... that's just my opinion and I could be wrong. I just based this on the assumption that the amp is fine and works properly at home. If the electrical installation in the jam-space is faulty and caused damage to the amp, it shouldn't be working ok back at home...

But I'll let more tech-savy people answer this, I'm probably not too far from useless anyways... I'll sit back and learn.

 

[Funkfingers]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

Looks like a simple case of lousy electricity supply. (Hopefully, not too many amp components have been damaged.) The phenomena that you describe remind me of what happens when somebody overdoes the Edward Van Halen variac trick.

I would thoroughly investigate the electricity supply set up in the storage facility. If the place is only expecting to power industrial lights, air conditioning, dehumidifiers and cleaning equipment, it may run on a three-phase supply and then step down to 110v for a few wall sockets.

Take care.

 

[BigDreamer]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

Ok so my plan as of now is next time I get out to the space I'll measure the voltages for the outlets and report back. I'll also try a few tube swaps in my friend's amp as well.

We're slowly, but systematically eliminating possibilities--thanks so far guys!

 

[Gearjoneser]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

I wonder if the excessive loading on the electrical outlets was causing them to overheat, and their breaker wasn't blowing because it's not the right one.

If you said it happened after 15 minutes, it sounds like a heat problem. And the problem was diminished when using a small SS amp, yet more significant when using the highest wattage amp you tested.

I don't know what happens to electrical wiring when it gets too hot, as far as effecting amps, but you might be very lucky the building didn't catch fire. Think about that before proceeding.

 

[Jessie Sammler]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

I'd definitely go back armed with an outlet tester, a multimeter, and maybe an oscilloscope. Don't take anything for granted. Test both sockets in every outlet that you use. Take voltage measurements (line-to-neutral and line-to-ground) before and after you plug in and power up your equipment.

If you find anything weird, get an electrician involved.

 

[glassman]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

my guess would be that you are getting a low voltage situation under load. As the wiring heats up, the resistance increases, dropping the voltage. If you test the voltage at your practice space, do it under load. Use a hair dryer to simulate an amp load and measure the voltage with it off and then on; there should be very little difference between the readings.

The switching network in Mesa amps can be damaged by low voltages. There are a bunch of LDR's (light driven resistors) that are acuated by internal LED's. If the voltage is low, the LED isn't as bright as it should be and the LDR has greater resistance; this would account for a greatly reduced output and a clean signal under all circumstances. This could be related to the power channel switching power supply; the first tube's filament is also powered by this power supply, so if it doesn't light up, the problem may be there.

I really think you need to get it to a qualified tech...one familiar with Mesa amps.

 

[uOpt]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

I'd definitely go back armed with an outlet tester, a multimeter, and maybe an oscilloscope. Don't take anything for granted. Test both sockets in every outlet that you use. Take voltage measurements (line-to-neutral and line-to-ground) before and after you plug in and power up your equipment.

If you find anything weird, get an electrician involved.

An outlet tester won't tell you whether the power collapses under load. It either has 0.0001% load or 100% load (aka shortcut to test the fuse).

You would have to monitor the voltage while the amp is sucking power. Good way to get zapped.

 

[uOpt]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

I wonder if the excessive loading on the electrical outlets was causing them to overheat, and their breaker wasn't blowing because it's not the right one.

I don't think so. A 100W tube amp draws power that isn't much more than a better lamp with a couple of 100W lightbulbs, not to mention an electric tea kettle or a dustsucker draw much more.

It would be very weird for the voltage to drop by some amount proportional to the amps drawn so that things look even remotely normal but blow the amp(s).

 

[uOpt]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

I know and I'm probably not as knowledgeable as you... that's just my opinion and I could be wrong. I just based this on the assumption that the amp is fine and works properly at home. If the electrical installation in the jam-space is faulty and caused damage to the amp, it shouldn't be working ok back at home...

But I'll let more tech-savy people answer this, I'm probably not too far from useless anyways... I'll sit back and learn.

I'm not particularly knowledgeable at all. I'm just saying that the observations don't add up to leaving any one theory intact and that careful re-evaluation of the observations is required.

On the other hand, damaged electronics come back to live for me all the time, so you can't rule anything out either.

 

[RLee]

Re: Mystery Problem Involving Tube Amps PLEASE HELP!

It definitely sounds like a power issue. The place doesn't have aluminum wiring, does it? I've seen some really bad power fluctuations in old buildings with that lousy aluminum wiring. The same thing could be caused by loose wiring at the AC plug -- the vibrations from the music would cause a loose wire to spark and create intermittent voltage spikes, which would be really bad for most equipment.
If it's loose wiring, a voltmeter might not catch it, since you'd likely need to shake it up to cause the problem.