Is it okay for my valve to glow purple?!

Tenson

Tenson

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I may have simply not noticed it before but the power choke valve on my pre-amp glows slightly purple! I first noticed when I turned it off after a long time on (I don't turn it off!) and then when I turned it back on after a few minutes it flickered very purple then grew to be red. When I look between the metal plates surrounding the wires that glow red I can see it is still pretty purple though. Is this normal or is it on the way out? It still sounds alright I think.

Can you see it in this picture?
 
I swapped out my 4 KT88 Svetlana's for Tesla's and the Tesla's have a definite purple tinge to them, esp under warm / voltage ramp up but still viisble in lower light.
Your's looks like KT88 but I could be wrong.

What voltage does your equipment run at?
Mine are set at 480V.
 
The spectra given off could show the metal contains some potassium.....other than that I would not like to comment.
 
Usually due to residual gas being ionised.

If however you notice hot spots on the valve plates,i.e.areas that glow red then thats a sign that the valve is being driven too hard.
 
I have the same rectifiyers (6AUG?) in my amps, they don't glow purple but the output ones (KT88) do?
 
I wonder if some manufacturers actually add gases that create attractive colours - the Sovtek KT66's I had in my Quads glowed really blue in low lighting conditions. Very nice, but not on a patch on the fireworks display I got when one of my Svetlana KT88's died. At least it went out in style.

On a slight side note; is it normal for some (ecc83/82) valves to briefly flash brightly on powerup?
 
My Amperex ECC82's flash at switch on, this is normal for some brands

If the blue glow seems to be on the glass then that should be ok
if theres any pink spots on the plates then this could be a problem
 


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