Tube went down- Amp still working?

[Gizzorge]

I am curious what are the effects of a power tubing going down in my V... Amp just faded out (volume), looked behind, had a tube glowing LAVA!!!

Turned amp off, later in the night, turned it back on, and it is still working. ????

What should i be noticing with 1 tube not working?

 

[Gizzorge]

Anyone?

 

[SamuelJ86]

I think I read this in the manual, but it's possible for a power tube to develop a short somehow. Usually glowing red like you described. And then un-shorting, or fixing, itself simply by shutting the amp down and turning it back on. I've not had this happen but wherever I read that at acted like its not uncommon. And if it's working fine again, you should be ok.

 

[Authorized Boogie]

I think I read this in the manual, but it's possible for a power tube to develop a short somehow. Usually glowing red like you described. And then un-shorting, or fixing, itself simply by shutting the amp down and turning it back on. I've not had this happen but wherever I read that at acted like its not uncommon. And if it's working fine again, you should be ok.

Intermittent shorts are a sign the tube is headed for failure, and should be addressed. Thanks!

 

[SamuelJ86]

Thank-you Boogie

 

[BigBadWolf]

There is not a simple, all covering answer available. And i'm far away from a guru. Just a person who has had to learn about these things. And all that not willingly even ;D So this is just wild guessing.

Mark V uses power tubes in many different ways/combinations (read the manual, 'cause that is too much to write here and now). So it is possible that in certain setups you won't necessarily notice one broken power tube. All tubes are not always in use.

Some general symptoms of worn/broken power tube are
- odd noises
- lack of power
- missing frequency
- silence

I tend to use phrase "tube amps use more magic than electricity" (basically to bug people with no sense of humor gotten in birth). That means you may be able to make your tube (i need lessons in technical english) in unstable state with some extreme setting and get out of it without immediate damage. What that phrase really means is tubes may do tricks only really skilled scientists can really understand. However after this kinda thing, your tubes are not going to live long.

The older your tubes are, the bigger possibility to get strange behaviour from them gets. And the tube itself is not always the main reason. There are many things which can effect to tube amps behaviour. Room temperature, quality of electricity, vibrations etc.

To rule out some possibilities you'd need to give a hint of your setup at the time, age of tubes, location of glowing tube (which one of them?) and such things. With this it is kinda hard to know what is going on.

Edit: Hm. Should've been short with words like the pro's who wrote their answer at the same time ;D

 

[jb's 52]

I am curious what are the effects of a power tubing going down in my V... Amp just faded out (volume), looked behind, had a tube glowing LAVA!!!

Turned amp off, later in the night, turned it back on, and it is still working. ????

What should i be noticing with 1 tube not working?

I just got a pair of tubes and one of 'em did the same thing.
Volume faded, tube glowing all red, and I switched it off.
I gave it a few minutes and turned it back on and the amp and tube were fine.
I think I'm gonna return it though since I just bought 'em.

 

[Gizzorge]

It's weird, I see no glow at all on that tube anymore the other 3 look fine, amp still sounds strong....

Also, thanks for all of the help people!!!

 

[Authorized Boogie]

If the tube is not glowing AT ALL and is cold to the touch, then its dead. The amp can still run, but will put a strain on the 3 remaining power tubes. Time for a change : )

 

[bandit2013]

I would agree, time for a change.... I have had intermittent issues with tubes, I have had one cut in and out but heater still active. Noticed the intermittent behavior with that particular tube loosing its blue hue on the inside of the glass, it would return periodically. Intermittent issues could be related to internal tube issue as most metallic contacts are made by sonic welding. Thermal changes may cause poor weld joints to crack resulting in intermittency. If you have this type of issue, replace the tube as the end result will be catastrophic to the other tubes.

If the heater is off on that tube, it may have a fracture in the glass envelope or internal issue and should be replaced.

If you red plated any of the tubes but seem fine after removing power, best to replace them. Sooner or later that tube will red plate again and hopefully only blow the fuse and nothing else. I would mark those tubes that have been overtaxed if you plan on using any of them later as backup. I would suspect the red plated tube to be one of the center pair as those usually run a bit hotter than the outer two.

 

[Nicklotsaguitars]

That red glow, your valves have red-plated.
Something has happened to the grid in the valve or the grid bias resistors in the amp. Causing too much current to flow from the cathode to the anode (plate). Them electrons hitting the plate cause the valve to become permanently changed.
Throw them valves in the bin, it's the only safe answer. And get your bias checked.