cloudy tubes

B

bobsheed

ronnie
Hi

Ive got an amp using 805's as output tubes and one of them seems to get cloudy inside the glass after about 1/2 an hours use. The other 805 is fine and clear, is the cloudy one faulty? It still sounds great even when its clouded up but I dont want to push it if its ready to pop.

I'd be grateful for any suggestions

Ronnie
 
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Bobsheed I'ver never heard what that could be but I'd be worried if it wasn't cloudy
before you turn it on but is after it runs.

Sounds like a faulty tube to me and I would replace it before it blows!

Maybe others here can chime in and say for sure.
 
Never heard of something like this before. Perhaps when it heats up the pores in the glass expand and its letting air in? Would seem like once that happens it would be kaput though. Personally, Id replace it.
 
thanks everyone for your replies

I'm not going to use the amp till I've replaced the tube, though its not easy finding replacements.

Ronnie
 
Strange usually when they get cloudy they stay that way. Is there anyway to check the bias on the tube in your amp? If you don't know check for a large wattage resistor attached to I believe pin 2 or 4 then going directly to ground. Measure the voltage on the tube pin side of this resistor and compare it to the other tube. A schematic would make this easier.

Craig
 
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