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Stephan1980

Power tube glowing red means what again?

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I noticed a burning smell coming from my amp so I checked the back and the 5881s were glowing bright red.

 

Time for new tubes or something else wrong?

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Where?

 

If the grey folded metal part is glowing cherry red...there's something wrong.

 

If it's just a light in the tube, you're fine...I'm guessing you know what a normally operating tube looks like and you've probably got a tube out of bias.

 

They may need to be replaced.

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yeah the plates were red... not just the element... it was in 50w mode... switched it down to 15w and they stopped glowing... after that I just shut the amp off.

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Red means it's going to launch.

 

All kidding aside, red tubes are very very bad, turn the amp off ASAP and don't turn it on again until a shop looks at it.

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I think the tubes can melt if they're in that state. I'd turn your amp off if I were you.

 

I thought the inner components have already begun to melt in each other when redplating occurs? :confused:

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Your tube sockets might be dirty. Give the tubes pins, and sockets a good whack with contact cleaner, and work the tube in and out a few times to establish good connections.

 

YOu might need to take a pick, and re-tension the sockets by bending them together to make the pins fit tight again. Make sure the amp is drained of power before you do this.

 

BTW, it's the tube beside the red glowing one that's the culprit. That's how it works.

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Means the flyback transformer is shot! Ooo wait.. that's old TV's :lol:

 

Time for new tubes! If it still red plates, amp needs some service.

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I thought the inner components have already begun to melt in each other when redplating occurs?
:confused:

 

it's more like the burner on your stove being red - it's not melting, just getting hot enough it starts emitting visible light, and in tubes that means the plate coatings are at risk of damage, which shortens life span. it's not an instant death sentence.

 

i've had tubes glow like light bulbs because of a faulty bias supply, then go on to continue working fine a couple years after having the amp fixed.

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The 3 major reasons why tubes redplate.....

 

 

1] Loss of plate voltage [Vp] to tube, or loss of B+ to O.T. center tap.

 

2] Loss of control grid bias voltage [-Vg.dc]...bad pin/socket

connection; open wiper or dead diode.

 

3] Tube itself, internal shorts between elements.

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This is a great article on tubes. Try reading it maybe then you guys won't come across as so ignorant.

http://www.vacuumtubes.net/How_Vacuum_Tubes_Work.htm

 

 

B. Guitar amps


In general, only very low-cost guitar amplifiers (and a few specialized professional models) are predominantly solid-state. We have estimated that at least 80% of the market for high-ticket guitar amps insists on all-tube or hybrid models. Especially popular with serious professional musicians are modern versions of classic Fender, Marshall and Vox models from the 1950s and 1960s. This business is thought to represent at least $100 million worldwide as of 1997.


Why tube amplifiers? It's the tone that musicians want. The amplifier and speaker become part of the musical instrument. The peculiar distortion and speaker-damping characteristics of a beam-tetrode or pentode amp, with an output transformer to match the speaker load, is unique and difficult to simulate with solid-state devices, unless very complex topologies or a digital signal processor are used.
These methods apparently have not been successful; professional guitarists keep returning to tube amplifiers.


Even the wildest rock musicians seem to be very conservative about the actual equipment they use to make their music. And their preferences keep specifying the proven technology of vacuum tubes.

 

Ohhhhh buuuuurrrrnnn :snax::snax::snax::snax:

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