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When to change valves!


Truckstop
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Hello all,

I have a valve amp and I was wondering how often I need to be looking at changing the valves. Is there a way in which I can test the efficiency or the life of the valves already in the amp?
Are there any other componants I need to look at in order to make sure it's in good working order?

If I do need to change valves, are there particular ones that I need to buy to match the amp or the power rating? Do valves even have a bearing on the power rating?

Any information gratefully received. Was thinking of sending it to a tech to give it a once over, but I'd like to know if there's anything I can do at home to see how well it's working.

Cheers

Alex

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Valves get tired at different rates, you can get valve testers, they generally reside with techs. Often, the bias drifts and you can hear the wrong, but a rebias sorts it. What valves depends on the amp, some have loads of options, others are more picky. My fancy Ashdown handwired job could take most standard power valves, but other amps will toast inferior valves or exploded if you put high draw vavles in. So depends on the amp.

Preamp valves are easier, there is less variation, and you can plug and play, bit of swapping shows the state of them.

Other components that have a chance of problems are: all of them, basically.

Electrolytic capacitors are the ones with a limited lifespan, even if the amp is unused (apparently more so if it is unused for a period), but resistors and capacitors can drift value, plus sockets and switches can corrode.

What amp is it, and how old, can give a bit more specifics that way.

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Cheers, thanks for the info.

I don't think anything's wrong with it, but because I've only had it for a couple of months, I don't know if it sounded 'better' a year or two ago if you know what I mean. Would you recommend getting it to a tech to make sure everything's hunky dory? It's from the 70's (no indication of date inside casing etc) and is made by an italian firm called Gem. The model is a Saturn Bass 50 and I simply cannot find any information on it anywhere! I don't know how well it's been maintained and I can't even see what valves it has, there's no markings or anything.

Truckstop

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[quote name='Truckstop' post='1358893' date='Sep 1 2011, 03:32 PM']Cheers, thanks for the info.

I don't think anything's wrong with it, but because I've only had it for a couple of months, I don't know if it sounded 'better' a year or two ago if you know what I mean. Would you recommend getting it to a tech to make sure everything's hunky dory? It's from the 70's (no indication of date inside casing etc) and is made by an italian firm called Gem. The model is a Saturn Bass 50 and I simply cannot find any information on it anywhere! I don't know how well it's been maintained and I can't even see what valves it has, there's no markings or anything.

Truckstop[/quote]

Do the valves not have any markings on them themselves? guessing they're gonna be EL34's in the power amp and ecc83s in the pre.

Basically you'll know when you'll need new valves because it'll start sounding a bit pants

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[quote name='Truckstop' post='1359074' date='Sep 1 2011, 06:15 PM']Well, that's the tricky part. It sounds awesome to my ears, but I'm not sure when it last got revalved (if ever) and i'm wondering if it'd sound even MORE awesome if it got revalved!

Truckstop[/quote]

if it sounds great why mess with it? don't think you'd be very chuffed with it if the valves were on the way out, it'd not be very loud and probably start blowing fuses.

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