we played a christmas fair at the school i teach at today, and half way through the set i realised (or i saw) one of my tubes in my valveking 212 was not lit up.. i assume this means it is dead. but i still got sound??
A) is one blown tube bad?
B) if i just run through my pod 2.0 into the effectsa return am i right that this bypasses the tubes and just goes straight to the speaker??
c) is there any dangher/possible damagbe to my amp doing this until i get another tube.
finally, do i need a tube that matches the others, i am aware there are different types??
"I like to play that guitar. I have to stare at it while I'm playing it because I'm not very good at playing it."
Noel Gallagher (who took the words right out of my mouth)
If the amp was still playing and sounding OK, I doubt you have a dead tube. Which tube was it, one of the two big 6L6s, or one of the little 12AX7s? It's common not to be able to see the glowing cathodes in a 12AX7.
If a tube's simply dead, you can't hurt the amp running it that way. The only tube failures that will hurt an amp involve excessive current flowing, as when air gets in a power tube. The tipoff is the bright red glow from the normally gray plate.
Before you notice it and ask, a blue glow on the inside of the glass is a normal, healthy thing with power tubes.
The effects return will bypass some of the little "preamp" tubes, but still goes through the power stage of the amp.
There is no need to match any "preamp" tube, nor is there any biasing necessary.
I would normally buy power tubes as a set, but wouldn't pay extra to have them specially matched. Amps usually have some imbalance between the two in a pair built into them anyway. I don't have time to download the Valveking owner's manual to confirm this, but I believe it has cathode biasing and doesn't need any adjustment when power tubes are replaced, either. Just replace the tubes when needed. It's a good idea to keep spares, but it's uncommon to have a sudden tube failure. (More common with new tubes, surprisingly.)
"A cheerful heart is good medicine."
more common with new tubes?? well i only had the amp 6 months and only use it when we gig (2/3 times a month) - so i suppose it has only been used no more than 18 times so it is quite new really.
when you ask which tube it was, i can only see 4 tubes through the grate in the back, and it was one of them (the one on the left). All the others had a bright glow to it and this gave nothing at all.
in the last gig we had the fuse in the amp (not the plug) blew, and this is the first time i turned it on after replacing the fuse. i am guessing the blown fuse also had something to do with it.
would a tube dying cause that, or is it a symptom of something more serious??
"I like to play that guitar. I have to stare at it while I'm playing it because I'm not very good at playing it."
Noel Gallagher (who took the words right out of my mouth)
more common with new tubes?? well i only had the amp 6 months and only use it when we gig (2/3 times a month) - so i suppose it has only been used no more than 18 times so it is quite new really.
New for the purpose of early tube death is generally in the first 24-48 hours of "powered on" time.
when you ask which tube it was, i can only see 4 tubes through the grate in the back, and it was one of them (the one on the left). All the others had a bright glow to it and this gave nothing at all.
That'd be one of the 6L6 power amp tubes. There are 2 pairs in a push-pull (Class B) configuration, as far as I can tell, If one tube was shut down, you'd get less output on one half of the waveform, but the amp would still be plenty loud.
in the last gig we had the fuse in the amp (not the plug) blew, and this is the first time i turned it on after replacing the fuse. i am guessing the blown fuse also had something to do with it.
that's a pretty safe guess.
would a tube dying cause that, or is it a symptom of something more serious??
Depends, which fuse? (there are 4 that I can see on the schematic, though some may be internal)
It's possible that the act of the tube dieing caused a temporary overcurrent, and took out the fuse. Since the replacement fuse didn't immediately pop, whatever caused it was probably temporary.
According to the manual, you've got a 2 year warranty from Peavey. Might just be the tube, but if they'll check it over on warranty, that should put your mind at ease.
I wrapped a newspaper ’round my head
So I looked like I was deep
A tube failure may not be covered under warranty, but Peavey's mighty good about standing behind their products. Check with them.
Peavey says on their website that this amp has a knob that'll let you dial it in anywhere from Class A to AB operation. That could mean a variable fixed bias, but I suspect it means cathode bias with a variable resistor. I haven't taken the time to download their user's manual, but it's on the site and will say whether new power tubes have to be biased or not. I think not.
(Class A push-pull preceded Class B and Class AB amp development. It used to be very common in audio equipment, the highly touted advantage being that it cancels out even order harmonics produced in the power stage. Many of us nowadays don't care about running our guitar amps super clean, but lots of early guitar amps were made with Class A push-pull output stages. I've got an old Airline AM-FM-phono console sitting next to me that runs a pair of Class A push-pull 6K6GTs. And a Hammond M3 organ on the other side of me that runs a pair of Class A push-pull 6V6GTs.)
"A cheerful heart is good medicine."
Peavey says on their website that this amp has a knob that'll let you dial it in anywhere from Class A to AB operation. That could mean a variable fixed bias, but I suspect it means cathode bias with a variable resistor. I haven't taken the time to download their user's manual, but it's on the site and will say whether new power tubes have to be biased or not. I think not.
It's labeled as "texture" on the amp, and is on the back panel.
If I'm reading the manual and the schematic correctly...
What the "texture" knob does is to reduce the input level to one pair of 6L6 tubes.
If that pair happens to be the one containing the dead tube, your dead tube has essentially turned the texture knob partway to the left.
I wrapped a newspaper ’round my head
So I looked like I was deep
If that's what it does, it seems to be advertised misleadingly. Haven't read the manual and schematic, though. Maybe they mean one pair of 6L6s is run Class A, one is run Class AB, the output is blended, and the inputs can be panned to one pair, the other, or both?
"A cheerful heart is good medicine."
That makes sense.
I haven't done the math on the resistors surrounding the 6L6s, but it sounds like a good theory.
I wrapped a newspaper ’round my head
So I looked like I was deep
