Looks like I'm going back to solid state...

[greenspider]

So tonight my band had just finished setting up in our new(ghetto) jam space, and it only had one outlet. it forced us all to run power out of a couple of power strips for two guitar cabs, The P.A. and myself. Im running out of my new used peavey classic 50/50 tube power amp into and SWR 4x10 bass cab. After about an hour of practicing, i could smell something burning, as well as the drummer and we all stopped to figure it out. Its my peavey smoking up It sucks even more for the fact that i spent what money i had left in my bank. I'm pretty sure it burned up because of under powering it, but I'm wondering if anyone on here has had this problem with this type of amp, or tube amps in general.

[JMarkD]

I am no engineer, but in my experience, "under powering" a tube head should do no more harm than blowing the fuse. I had this happen years ago when my old 400+ was plugged into an outlet on a dimmer and someone decided to lower the lights! The voltage drops and the amp tries to draw more power causing the amperage to exceed the fuse rating.

Have you checked the tubes etc? Does the amp still work? There may be some other problem not related to the voltage situation. Also, if the amp has the wrong fuse installed, that might cause a problem. At any rate, sounds like Tech time.

I'm sure others more schooled in electrical stuff (hey, that stuff can kill you) will weigh in with more info, but this has been my experience in a low voltage situation.

[i_got_a_mohawk]

I'm not sure if it caused the damage to your amp, but it does seem pretty daft to be trying to pull all that power from one outlet.

I don't know what the standard outlet fuses are in the US, but you must have been getting close to popping it from excess draw!

[Floyd Eye]

Don't give up on tube amps, just Peavey tube amps. Actually that's not even true. I hear some of Peavey's new tube amp offerings are awesome.

[MAMMOTHvolume]

smoke but the fuse didn't pop? sounds like it could've been something else getting extremely hot, did you check the outlet to see how hot that was getting?

[i_got_a_mohawk]

Originally Posted by Floyd Eye

Don't give up on tube amps, just Peavey tube amps. Actually that's not even true. I hear some of Peavey's new tube amp offerings are awesome.

Wouldn't agree with that, the Classic 400 was an awesome amp and most peavey tube guitar amps are also pretty awesome (5150/6505 anyone?!).

[tony_clifton]

I would never go back to solid state for guitar amps, but for bass... meh. I loooove my Terror Bass, it's extremely portable, costs about half the full tube Orange and sounds very close to it. I wonder if I ever buy a full tube.

[Wes Whitmore]

The real question is what was the condition of the tube amp before you got it, and how many times have you played it as loud as you did that night? Was your equipment the only one that had problems? It really sounds like your amp just plain failed after extended use that day.

My band runs everything off of 2 15 or 20 amp outlets, depending on what we can find. We have done it with 1 before as well, but usually only at acoustic gigs. We only use around 1800 watts of PA through some 12" 2-ways and a couple of JBL single 18s. No monitor amps. 2 Guitar amps, a bass amp (some form of a GK RB amp), some LED lights, two mixing boards with outboard EQs, compressors, Driverack, and our 4 Shure PSM200 in-ear transmitters. We have never tripped a breaker. We are not the loudest band you will ever hear though, but loud enough.
Wes

[Floyd Eye]

Originally Posted by i_got_a_mohawk

Wouldn't agree with that, the Classic 400 was an awesome amp and most peavey tube guitar amps are also pretty awesome (5150/6505 anyone?!).

I gave Peavey tube amps props up there. (5150/6505 are both modern Peavey tube amps, which as I already stated are pretty cool)

I disagree that most of them are awesome though. Of course this is dependent on tone, which is totally subjective. For example I have a friend with a "Classic 50" or whatever they're called. He loves it. I wouldn't give you 8 bucks for it. Then again, I am certainly an old vintage tube snob. I like my 61' brown and if I could afford or find one I'd be looking for an early 70s 300 watt Ampeg bass head.

All subjective guys, my real point is that tube amps in general have nothing to do with the OP's dilemma and he shouldn't be so quick to dismiss them.

[craig.p]

Maybe one of the tube-amp experts can answer this: is it possible for the line voltage to drop low enough that a capacitive-divider bias circuit will allow too much plate current despite the drop in plate voltage?

I don't know the Peavey's topology, i.e. whether it uses this type of bias circuit. So I guess this is more of a theory question.

Thanks in advance.

[i_got_a_mohawk]

Originally Posted by Floyd Eye

I gave Peavey tube amps props up there. (5150/6505 are both modern Peavey tube amps, which as I already stated are pretty cool)

I disagree that most of them are awesome though. Of course this is dependent on tone, which is totally subjective. For example I have a friend with a "Classic 50" or whatever they're called. He loves it. I wouldn't give you 8 bucks for it. Then again, I am certainly an old vintage tube snob. I like my 61' brown and if I could afford or find one I'd be looking for an early 70s 300 watt Ampeg bass head.

All subjective guys, my real point is that tube amps in general have nothing to do with the OP's dilemma and he shouldn't be so quick to dismiss them.

The 5150 first came out almost 20 years ago, I wouldnt call that modern

Tone is subjective, but peavey gear is built to last IME.

The classic is a nice amp (I had a classic 30 combo for a while), but the classic 50 and the classic 50/50 aren't the same thing at all .

And at least with the ampegs there are the new VR's and even if you do want vintage, they aren't exactly rare!

I agree with your last point. Tube amps only become more fragile if people start smashing the tubes!

[Bassmec]

Running a tube amp on a variac to lower voltage and increase distortion/saggyness! is a pretty common trick in UK studios.
I cant think what reaction its going to be increasing current when you lower voltage.
What makes Tube amps very unhappy is running into the wrong output impedance for the transformers tapping.
And amps that are not set with the correct bias for the tube set thats in them.
My bet is that its the latter of those two issues.
What was the bias currant set at and was the person responsible wearing a clown hat at the time.
Over here we are on 250V thus trusted by our government with voltages capable of causing a little more damage, death and discomfort.
With the added slight advantage that we can leave large amounts of central and southern Africa in situ for the same number of watts.
Campain, Lobby!. Even kidnap senators pets! but come to the attenshion of the press.
Let this be your slogan! NO MORE HALF ARSED ELECTRICITY
Take a leaf out of
http://www.clairsystems.com/
Book 110v is not enough with any kind of cable run.

[countrybass007]

In my experience the fuse blows before really bad things happen. Hopefully, this is the case in your situation.

[jastacey]

I've got a question ... did you check what the Ohm's is for the cabinet and is there a Ohm switch on the amp ...what was it set at? Maybe the smell was the OT smoking, because of a ohm mismatch?

[Floyd Eye]

Originally Posted by i_got_a_mohawk

The 5150 first came out almost 20 years ago, I wouldnt call that modern

Tone is subjective, but peavey gear is built to last IME.

The classic is a nice amp (I had a classic 30 combo for a while), but the classic 50 and the classic 50/50 aren't the same thing at all .

And at least with the ampegs there are the new VR's and even if you do want vintage, they aren't exactly rare!

I agree with your last point. Tube amps only become more fragile if people start smashing the tubes!

Well, I certainly am no Peavey expert.

I do know that I started out on Peavey gear and they are definitely built to last. That doesn't mean I think they sounded particularly good though. And I don't think their "Vintage" tube amps are too much to brag about. If they were people wouldn't be spending their inheritance on Marshall plexis.

[Walking]

Low voltage would make a tube amp less hot rather than more. Van Halen used a variac to dial down his marshall voltage to get more distortion. People who repair old tube gear use a variac to dial the voltage up from zero to form the caps.

I think your amp blew because some part failed. Its a drag, but the peavy units are built to a price point...

Solid state amps, on the other hand don't like low voltages. Voltage regulators try to hold a certain voltage output, and when the input drops too low, they may not handle it gracefully. For a solid state amp, note the specified voltage range and make sure the wall socket can deliver it. Having said that, I doubt that the voltage in your practice room dropped too low, or the circuit breaker would have tripped.

[Walking]

Originally Posted by craig.p

Maybe one of the tube-amp experts can answer this: is it possible for the line voltage to drop low enough that a capacitive-divider bias circuit will allow too much plate current despite the drop in plate voltage?

I don't know the Peavey's topology, i.e. whether it uses this type of bias circuit. So I guess this is more of a theory question.

Thanks in advance.

Its an interesting thought, but as the plate voltage drops, the needed bias would drop proportionally.

I have seen circuit board traces fry from time to time, but one thing that will make a tube amp cook is when the caps between the driver plate and the power tube grid fails. Dc starts coming into the grid, the plate of the tube starts to glow, and the tube live can be measured in minutes once the plate is glowing...

[Bassmec]

Had a look at the amps PDF
I see you have one cab and two channels of tube power amp, is the cab wired for stereo, did you get it right, where the speaker cables in good order, was the output selector set to the correct
ohms for the impedance of the cab?.
If only one channel of the amp was connected what was the position of the standby switch for the amp not connected to a loudspeaker.
It all smacks of self inflicted sabotage to me skipper!.

[craig.p]

Ok, Walking, thanks for that.

I took a set of characteristic curves and plotted a 10% reduction in plate voltage and a 10% reduction in grid voltage, and came up with a plate current on the (new) curve that was much further down on that curve, in fact down into its nonlinear region's top end. Which lines up with what you said.

It was the "proportionally" part I wasn't sure of.

[i_got_a_mohawk]

Originally Posted by Floyd Eye

Well, I certainly am no Peavey expert.

I do know that I started out on Peavey gear and they are definitely built to last. That doesn't mean I think they sounded particularly good though. And I don't think their "Vintage" tube amps are too much to brag about. If they were people wouldn't be spending their inheritance on Marshall plexis.

That's because Marshall has the Fender effect.

If I want a vintage plexi, I'll just make my own for a couple hundred quid, they're surprisingly simple (not that thats a bad thing!)