How do you tell when powertubes go bad?
- Thread starter grunge782
- Start date
Capulin Overdrive
New member
some 5881's get lots of blue.
power tubes just seem to get gradually tired, so if you're getting tired of your sound could be time for tubes.
when i just had one amp, i figured about a year for SED's with lots of playing and about 6 months for Chinese.
power tubes just seem to get gradually tired, so if you're getting tired of your sound could be time for tubes.
when i just had one amp, i figured about a year for SED's with lots of playing and about 6 months for Chinese.
glpg80
Well-known member
blue haze inside a tube means that the tube is considered "gassy" - under heavy loads either from sheer volume or mis-matched impedances (done properly here - not the kind that cook OT windings). tubes should not glow blue under normal load.
if they do glow blue it means the tubes are on their last stance, and prone to failure.
biasing too hot can cause tubes to prematurely become gassy - causing the blue haze.
the only orange/red you should see in a tube are the heater filaments inside the tube where the anode and cathode are located.
the outer-edge plates of the tube should never glow red, this is a sign of thermal run-away, bias runaway, or prone to premature tube failure. usually this is the case for attenuated amplifiers running wide open for a very long period of time without proper ventelation.
proper ventelation for tubes do help tremendously to extend their life-span.
if they do glow blue it means the tubes are on their last stance, and prone to failure.
biasing too hot can cause tubes to prematurely become gassy - causing the blue haze.
the only orange/red you should see in a tube are the heater filaments inside the tube where the anode and cathode are located.
the outer-edge plates of the tube should never glow red, this is a sign of thermal run-away, bias runaway, or prone to premature tube failure. usually this is the case for attenuated amplifiers running wide open for a very long period of time without proper ventelation.
proper ventelation for tubes do help tremendously to extend their life-span.
glpg80
Well-known member
grunge782":8lcsrqkf said:
a normal tube should thud. it should not ring like a bell, and it should not rattle when hit. if there is rattling, then the tube has failed - probably from thermal damage or mechanical deffects in production.
if the tube sounds like a bell then its microphonic which is what happens normally with tubes - and only gets worse when heat is included in this variable. i always tap tubes with a wooden pencil slightly to tell. you dont want to touch a power tube - it will burn the piss out of you if it is on. you also want to keep fingerprints off of tubes, as it can cause hot-spots on the glass in reaction to the gas when the tube is on.
glpg80
Well-known member
nope, not at all. the volume you play at will only speed up a tube's wear time. but as long as the amplifier is on - your tubes are counting down their days.
as far as matched goes - when it comes down to it - matching only helps to keep the lifespan close because the bias will be simillar to each tube.
since your amplifier is fixed bias, its probably biased cold. i have yet to find a company that fix-bias' their amplifiers hot - that wouldnt make any sense.
but a hot bias will cause tubes to wear quicker, as if you were playing at higher volumes on a cold-biased power tube. 6 one way, half a dozen of another. kinda like comparing front wheel drive to rear wheel drive - you see both at the drag strips and both will get you down the road pretty quick.
good luck on the tubes. i prefer http://www.thetubestore.com for my matched quads of power tubes. i will only order pre-amp tubes from http://www.dougstubes.com because he is the only person that does burn-ins on all of his preamp tubes to check for microphonic or deffective tubes out of the box. this means high gain 12ax7/ecc83 tubes have less of a chance breaking down in the future.
rock on bro.
as far as matched goes - when it comes down to it - matching only helps to keep the lifespan close because the bias will be simillar to each tube.
since your amplifier is fixed bias, its probably biased cold. i have yet to find a company that fix-bias' their amplifiers hot - that wouldnt make any sense.
but a hot bias will cause tubes to wear quicker, as if you were playing at higher volumes on a cold-biased power tube. 6 one way, half a dozen of another. kinda like comparing front wheel drive to rear wheel drive - you see both at the drag strips and both will get you down the road pretty quick.
good luck on the tubes. i prefer http://www.thetubestore.com for my matched quads of power tubes. i will only order pre-amp tubes from http://www.dougstubes.com because he is the only person that does burn-ins on all of his preamp tubes to check for microphonic or deffective tubes out of the box. this means high gain 12ax7/ecc83 tubes have less of a chance breaking down in the future.
rock on bro.
glpg80
Well-known member
did you give them your plate voltage when you ordered it, or have a technician look at it to order them? or did you order them at 37mA draw without any measurements?
if thats the case, then yes, they probably are cooking hot and/or deffective. 55-60% plate dissapation is what tubes should be biased at for high gain amplifiers. you would need to know exact numbers of your amplifier to get the correct tubes to do this and still stay outside of crossover distortion which happens when tubes are biased too cold.
if thats the case, then yes, they probably are cooking hot and/or deffective. 55-60% plate dissapation is what tubes should be biased at for high gain amplifiers. you would need to know exact numbers of your amplifier to get the correct tubes to do this and still stay outside of crossover distortion which happens when tubes are biased too cold.
glassjaw7
Well-known member
Hey grunge, I also run 77's in my recto. Been running the same pair for about a year and a half with no problems. I ordered JJ's from Eurotubes. Since then I've heard many complaints of their QC, but the tubes that I have still sound great to this day.
I'm not sure what "grade" my tubes are, I just know that they told me they were 29's on the phone. I told them I didn't want the high gain option because the recto has so much gain that its not all usable anyway. You could give them a call. They are VERY helpful and know a lot about running different tubes in all kinds of amps. 503-659-7401
BTW, heard great things about SED EL34's in the rectos.
I'm not sure what "grade" my tubes are, I just know that they told me they were 29's on the phone. I told them I didn't want the high gain option because the recto has so much gain that its not all usable anyway. You could give them a call. They are VERY helpful and know a lot about running different tubes in all kinds of amps. 503-659-7401
BTW, heard great things about SED EL34's in the rectos.
grunge782
New member
glassjaw7":dlphra57 said:
Nice. I figured kt77 would give the el34 recto love with some more range to it. I like the sound, but I wanted to make sure things were running properly you know?
I got my tubes from a different vendor so I think that reading would be different based on what they ran their voltage at.
glpg80":3a4m81vt said:
Once again, a little bit of blue haze is normal. If you replace every set of tubes you run across with some blue haze in them you are going to throw away a lot of money. And honestly, I'm not sure I've ever seen a set of tubes without at least a small amount of blue in them, on any amp.
