M125 monblocks.
First 2 pics are the tube in question, the other 2 pics are from the other monoblock.
There is some red on the left upper of the tube, just noticed it.
What happens if I let this tube fail, will it take out other tubes, caps, etc.,?
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Jim McShane wrote:Whether red on the plate is a sign of imminent meltdown is not a "cut and dried" determination. A small area of red plating is generally not a precursor to meltdown - in fact it is/was often considered normal and was mentioned in owner's manuals, etc. Some tube data sheets also mention that a small amount of red is normal and acceptable as well.
But large areas of red are certainly detrimental - it's an indication of overheating which is not good. Even if catastrophic failure does not occur it certainly is not beneficial for long tube life.
jfine wrote:Switched the 5AR4's between the 2 M125's, the same tube displayed the red, so it followed the tube.
Let's suppose it is beginning to fail, if I let this tube fail, will it take out other tubes, caps, etc.,? If it just fails on its own and doesn't damage anything else, I would just run it til it dies. If there's impending danger, then I probably should not turn the amp on again until it's replaced...
peterh wrote:
Order a new. Or two. During delivery delay use the amp as usual ( but not unattended), the fuse might not protect from a failing 5ar4 so keep a close watch.
jfine wrote:peterh wrote:
Order a new. Or two. During delivery delay use the amp as usual ( but not unattended), the fuse might not protect from a failing 5ar4 so keep a close watch.
So ideally, in the M125 anyway, the fuse *should* catch it, but is it an unknown set of possibilities of what might happen if it were to fail?
The single fuse is installed at the mains inlet, and is large enough to cope withjfine wrote:peterh wrote:
Order a new. Or two. During delivery delay use the amp as usual ( but not unattended), the fuse might not protect from a failing 5ar4 so keep a close watch.
So ideally, in the M125 anyway, the fuse *should* catch it, but is it an unknown set of possibilities of what might happen if it were to fail?
deepee99 wrote:jfine,
Some perfectly healthy tube rectifiers kinda sorta look like they're red-plating because you're looking mostly at the filament, but from the pix it looks like you've got a problem, Houston. That tube ain't going to heal itself; get it out of there before it hurts something.
If you already done the "yellow sheet mod" you don't have to worry. A shorted 5ar4jfine wrote:deepee99 wrote:jfine,
Some perfectly healthy tube rectifiers kinda sorta look like they're red-plating because you're looking mostly at the filament, but from the pix it looks like you've got a problem, Houston. That tube ain't going to heal itself; get it out of there before it hurts something.
So give me the blow by blow scenarios what *could* happen, take out a transformer, catch fire, take out all my power tubes, fry caps/resistors, ?
Call me a masochist but half of me wants to see what happens, watch the tube fail and the amp just shuts down, that would be a learning experience...but start costing me $$$ then I'll pass...
Checked bias and it's dead on, in fact, it only changed since I had these amps, when I added the yellow paper diode mods...
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