When to replace valves....?

[rakh1]

Hey all,

I have an old Studiomaster 2x100W all valve head unit.
My question is how do I know when it is time to replace the valves? Does the sound get worse as they get older (like strings) or is it the case that as long as they work they are fine (like a lightbulb)?

Any suggestions welcome...

R

[fett]

Re: When to replace valves....?

Tubes, valves, will last a long time. Let your ears tell you when to replace tubes. Eventually the sound will deteriorate and you will notice it. It will sound muddy or you will hear microphonics.One thing, though. Every once in a while look at your tubes while the amp is on. Don't touch anything!!!! If they seem very hot or are glowing red hot, unplug it. Good tubes are built to last a long time and I think people change their tubes when they don't really have to. I have used tubes that are 50 years old and they still sound fine. [img]/images/graemlins/headbang.gif[/img]

[rakh1]

Re: When to replace valves....?

Hey - thanks for the reply. The valves glow a little but not bright red or anything. My best guess is that they are 15 to 20 years old. However, they have been outside for year or two at some point - would the cold or moisture have damaged them?

Cheers - R

[fett]

Re: When to replace valves....?

[ QUOTE ]
Hey - thanks for the reply. The valves glow a little but not bright red or anything. My best guess is that they are 15 to 20 years old. However, they have been outside for year or two at some point - would the cold or moisture have damaged them?

Cheers - R

[/ QUOTE ] Yikes!!! Was the amp outside? I would strongly suggest you get it checked out by a tech. As for the tubes being outside, the pins may have oxidation on them and should be cleaned. But, all in all, that exposure shouldn't affect them. If you are not familiar with tube amps let a tech do this. There is stored up electricity that can shock you long after the amp has been unplugged. BEWARE!!!!!!!

[rakh1]

Re: When to replace valves....?

Cheers - I'm an electronics graduate and MIEE so have a pretty good idea of what's what - however, I did digital electronics so valves are somewhat of a 'voodoo-magic' mystery [img]/images/graemlins/wink.gif[/img]

The amp was outside but appears to have not suffered. I see no obvious oxidisation on any of the contacts. In fact - other than little dusty nothing was untoward.

I might take the head to the local guitar store - they should have a pretty good idea if the valves sound knackered or not....

Cheers - R

[adrenaline junkie]

Re: When to replace valves....?

What kind of amp is it? how the heck did it getleft outside for a couple years?? [img]/images/graemlins/crazy.gif[/img]

[fett]

Re: When to replace valves....?

Maybe, it went on an extensive 'amping trip in Sherwood Forest. [img]/images/graemlins/smile.gif[/img]

[rakh1]

Re: When to replace valves....?

'amping trip - BWAHAHAHAHAHAHA

It is an old StudioMaster head unit (my Dad used to be MD of StudioMaster when I was young). The amp was used heavily when I was at school and when I went to Uni I sold it to my brother. 4 years later I find he has hardly used it and that it is in an old shed along with the 2 1x12 Celestion speaker cabs I made. My Mom had even tried selling it but the only person who ever showed intrest at £15 (OMG £15!!!) didn't really know what it was (and nor did my Mom). So - I rescued the amp and the 2 cabs.

It turns out that they all work fine still. I was more worried about the speaker cones going bad after the moisture and cold but they appear ok.

Only think I am unsure of was if the valves needed changing...

R