Does anybody know iff this is normal..(valves)

Barney

I just turned my amp around to measure it for a cover and noticed the valves...is this normal...they look as though they are over heating or something 

digitalscream

Need a bigger photo, dude - the reflections make it pretty hard to tell at that size.

Barney

digitalscream said:

Need a bigger photo, dude - the reflections make it pretty hard to tell at that size.

Ok ...thanks will take one out and post again...

Barney

Ok ...this is a better pic i think

martinw

If you mean the silvering on the inside of the glass, that is perfectly normal. Part of the manufacturing process.

It's a pump!     

Barney

martinw said:

If you mean the silvering on the inside of the glass, that is perfectly normal. Part of the manufacturing process.

It's a pump!     

Ahhh...yeah thats what i was meaning ... thanks .. i will give myself a slap now  

Kalimna

Am i correct in thinking that the silvering is from the 'getter' which is a chemical reaction to remove as much 'air' as possible once the manufacture of the valve structure is complete?

Adam

martinw

Kalimna said:

Am i correct in thinking that the silvering is from the 'getter' which is a chemical reaction to remove as much 'air' as possible once the manufacture of the valve structure is complete?

Adam

Yes. Not air though as you imply. Actually Oxygen I think.

ICBM

Kalimna said:

Am i correct in thinking that the silvering is from the 'getter' which is a chemical reaction to remove as much 'air' as possible once the manufacture of the valve structure is complete?

Yes - and they deliberately put in too much so the remainder will mop up any tiny amount of air that leaks in over the course of the valve's life. If you see the getter flash becoming thin/semi-transparent or a sort of dirty pink colour, it's more or less used up and the valve doesn't have long left even if it seems to be working OK at the moment.

jpfamps

It usually barium, which reacts with both oxygen and nitrogen to help maintain the vacuum in the valve.

Kalimna

Cheers for the extra info. I had used the word 'air' as i made the assumption that the valve manufacturing plants did not have de-nitrogenation. I just wasnt sure what would mop up both oxygen and nitrogen.
Cheers,
Adam

jpfamps

Kalimna said:

Cheers for the extra info. I had used the word 'air' as i made the assumption that the valve manufacturing plants did not have de-nitrogenation. I just wasnt sure what would mop up both oxygen and nitrogen.
Cheers,
Adam

It also mops up gas released from the internal structures, for example mica used for spacers has a significant water content.

This is why valves overheating is bad as it can cause release of gas from internal structures.

The valve elements are "sparged" with hydrogen before assembly to reduce adsorbed gas too.

John_A

jpfamps said:

The valve elements are "sparged" with hydrogen before assembly to reduce adsorbed gas too.

Well that's a new word I've learnt today

Kalimna

Again, very interesting, thank you.
I know of sparging from the glorious process of beer making, but not this usage.

Cheers,
Adam

Bridgehouse

You guys talk about stuff sometimes that is so far above my head that it could see the curvature of the earth (er, or not)

Cabicular

Ok I'll lol that

Bridgehouse

Cabicular said:

Ok I'll lol that

I'm genuinely amazed by the knowledge of some folks on here sometimes..! (joking aside, that is)