#1
So I was playing my amp, then I get a lot of popping, and one power tube is much brighter than the other. Also, burning smells were coming from my amp. I turned it straight off.

Whats the problem? Are the powertubes on the way out?
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#3
Sounds like it. How long have they been in for? By the sounds of it you need to replace them.
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#5
Well obviously I wasn't actually PLAYING my amp, but..yeah.

They've been in since I got the amp. About 6th Months. I need this amp next friday...and I guess I have to get the amp re-biased as well. Bah! Also, if it's of any relevance (it might explain the tube wearing so fast) I have a lower Ohmage speaker in there (It's 8Ohms, and my amp is rated at 16).

P.S Before you get all flamey and scared about my amp being mismatched, a tube amp can easily survive lower ohmage mismatch. It just wears the power tubes out faster.
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#6
if you bought your amp from a music store, its possible that the tubes are already worn out from the in store playing. i would just simply try changing all the tubes and if the problem persists, id take it to a shop to see if a fuse has shorted out or something of that nature.
#7
Quote by bartdevil_metal
So I was playing ON my amp, then I get a lot of popping, and one power tube is much brighter than the other. Also, burning smells were coming from my amp. I turned it straight off.

Whats the problem? Are the powertubes on the way out?


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#8
Quote by HIM%(^
if you bought your amp from a music store, its possible that the tubes are already worn out from the in store playing. i would just simply try changing all the tubes and if the problem persists, id take it to a shop to see if a fuse has shorted out or something of that nature.


I bought it brand new from GAK.co.uk. And surely if it was a fuse then the amp would stop working altogether?
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#9
The fuse should have gone by now, if the valves are drawing too much current. Either way a new set of power tubes are the way to go, and your safe mismatch may well be the reason they've worn out so quickly.
#10
Quote by bartdevil_metal
P.S Before you get all flamey and scared about my amp being mismatched, a tube amp can easily survive lower ohmage mismatch. It just wears the power tubes out faster.


you may have answered your question there. yes you can mismatch within reason. yes it does cause strain on the tubes and they appear to be dying... get new ones then. sorted.
Thank you please.
#11
Quote by deadlydunc
you may have answered your question there. yes you can mismatch within reason. yes it does cause strain on the tubes and they appear to be dying... get new ones then. sorted.


Yeah, I thought that might be the reason, I just didn't know if the tubes were broken, as there's been no degradation of sound that I can spot. If I continue to play on it, will it damage anything else?
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#12
Quote by bartdevil_metal
Well obviously I wasn't actually PLAYING my amp, but..yeah.

They've been in since I got the amp. About 6th Months. I need this amp next friday...and I guess I have to get the amp re-biased as well. Bah! Also, if it's of any relevance (it might explain the tube wearing so fast) I have a lower Ohmage speaker in there (It's 8Ohms, and my amp is rated at 16).

P.S Before you get all flamey and scared about my amp being mismatched, a tube amp can easily survive lower ohmage mismatch. It just wears the power tubes out faster.


so, what youre saying is...

your power tubes wore out faster than tubes normally do?

and you're running at a different impedance, so power tubes wear out faster?


nah sry guys im stumped on this one
Get off this damn forum and play your damn guitar.
#13
You probably burned out your tubes with the lower ohms than you're supposed to use. Think of what ohms are a measurement of...resistance. Your amp requires a speaker load to keep from frying it's tubes and OT, and you're putting less of a load on it than it needs.

New tubes, and match those ohms. You can run and 8 ohm amp into a 16 ohm cab, but not the other way around.
#14
You've got it the wrong way round. Do that and you'll fry the OT. Trust me on this. Tubes can take lower ohmage than they're rated but not higher.

Quote by stevo_epi_SG_wo
so, what youre saying is...

your power tubes wore out faster than tubes normally do?

and you're running at a different impedance, so power tubes wear out faster?


nah sry guys im stumped on this one


I need to know if they are in fact on the way out and need to be changed. I know WHY they're going to/have already wear/wore out already.
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Last edited by bartdevil_metal at Apr 4, 2008,
#16
Quote by the.spine.surfs
Hey, you're the guy with the fried tubes.


I appreciate that you're trying to help, but all I need to know is some tell tale signs of when the power tubes are dying. I know about the problems of ohmage mismatch.
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#17
Sorry, sorry. What kind of burning smell? If it's like fireworks, it's something like bad wiring. If it's something else, it could be your OT, or just tubes.

It really does sound like a dead tube, if nothing else. Is the amp quieter?
#18
if it has 4 power tubes you can take 2 out and run it at half power, and see if its fine with only good ones
Get off this damn forum and play your damn guitar.
#19
Quote by stevo_epi_SG_wo
if it has 4 power tubes you can take 2 out and run it at half power, and see if its fine with only good ones

The ohm load changes, though. Doubles. Or halves...check the tube thread.
#20
Quote by bartdevil_metal
You've got it the wrong way round. Do that and you'll fry the OT. Trust me on this. Tubes can take lower ohmage than they're rated but not higher.

I've heard this on other forums too. But things I've owned with published manuals say otherwise. Look in any mesa manual, and they will tell you it's safe to use one step with a higher impedance cab/speaker, they refer to it as a safe mismatch. They even go as far to tell you why the tone changes, because the transfomer is pushing less current, so it runs cooler, which affects the tone. The THD manual states that you can use a higher impedance cab with their attenuator, but the tone will be affected. Both explicitly say not to run a lower impedance cab. I've worked out the math too, the transformer is pushing more current than it was designed for with a lower impedance cab, so you are stressing it along with the tubes. With a higher impedance cab mismatch, it's when you go more than one step, where you can get flyback voltage arcing in the tranny from the built up energy. I think you are playing with fire mismatching in that direction man.

BTW, you redplated the tubes, that's why you smelled burning and it lit up bright. The tube is most likely cooked, even if it works. And don't keep using it, if you get a major short, you can take out other parts of the circuit.

Quote by the.spine.surfs
The ohm load changes, though. Doubles. Or halves...check the tube thread.

pulling tubes takes out half the circuit path, so you've doubled impedance on that side of the circuit. With a matching impedance output transformer, now the taps are also doubled, ie. 4 ohm setting is now really 8ohm, 8ohm setting is now really 16ohm.
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Last edited by Erock503 at Apr 4, 2008,
#21
There you go. So if you pull tubes, you'll have a 32 ohm amp, and you'll fry the remaining tubes when you try to play it through your 8 ohm cab.
#22
Quote by Erock503
I've heard this on other forums too. But things I've owned with published manuals say otherwise. Look in any mesa manual, and they will tell you it's safe to use one step with a higher impedance cab/speaker, they refer to it as a safe mismatch. They even go as far to tell you why the tone changes, because the transfomer is pushing less current, so it runs cooler, which affects the tone. The THD manual states that you can use a higher impedance cab with their attenuator, but the tone will be affected. Both explicitly say not to run a lower impedance cab. I've worked out the math too, the transformer is pushing more current than it was designed for with a lower impedance cab, so you are stressing it along with the tubes. With a higher impedance cab mismatch, it's when you go more than one step, where you can get flyback voltage arcing in the tranny from the built up energy. I think you are playing with fire mismatching in that direction man.

BTW, you redplated the tubes, that's why you smelled burning and it lit up bright. The tube is most likely cooked, even if it works. And don't keep using it, if you get a major short, you can take out other parts of the circuit.


pulling tubes takes out half the circuit path, so you've doubled impedance on that side of the circuit. With a matching impedance output transformer, now the taps are also doubled, ie. 4 ohm setting is now really 8ohm, 8ohm setting is now really 16ohm.


lil something tells me you should listen to this dude....
Get off this damn forum and play your damn guitar.
#23
Well, I e-mailed Peavey about it when I first realised it was the wrong speaker - I had thought my amp WAS 8 Ohms until I read the manual - and the guy said it was safe. Hang on, I'll quote the e-mail.

Quote by Roger Crimm, Peavey
Hello Lee,

The amp is designed to use a 16 ohm speaker, and that is what is
recommended.
You can use an 8 ohm speaker, but the amp will run a little hotter and your
headroom will be reduced, along with slightly reduced tube life.


Regards,
Roger Crimm
Regional Service Manager
Peavey Electronics
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