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previous: Doc I agree not to replace a tube that'... -- 2/1/2000 4:35 PM

Re: Driver tube mandatory w/p.tube change?

2/2/2000 6:50 PM
lion	Re: Driver tube mandatory w/p.tube change? This thread got me thinking. A few years back – at the time when I had absolutely no idea what was going on inside a tube amp – I (as many other ignorante musicians) solely relied on the wisdom of my local music store. More than once I’ve seen the shops in-house tech pull a tube – look at it – and say: This tube is reeeaaally bad – better replace it! Since then I’ve learned a lot – thanks to this board and all the folk here willing to share their knowledge – and, come to think of it, havent’ visited the music store for a long time. But I’m still trying to learn – so I was wondering: Are there any reliable visual sign on tubes wearing out at all? I’m talking output tubes of course – I know preamp tubes can look perfectly new and yet be defective. (Uuuuhh, - so could output tubes, I guees...!) Trying to find some clues, I looked at a few of my used tubes. I keep them as spares. OK, they all looked used to some degree – and some a little burned due to the heat, but what does one actually have to look for to tell the condition? And what about preamp tubes? I’d also like to know if there’s any measurings – apart form using a real tubetester or transcon-something-meter, which I don’t have – that can be done to verify or indicate the condition of a tube? I’ve discussed some of these thoughts with one of my clever freinds, who said: Put the tube in an amp – if it works the tube is OK, if it doesn’t ...! Of course he’s right – but I’d like to be able to make a more detailed valuation. Sorry for the rambling. Regards Lion

2/2/2000 6:50 PM

lion

Re: Driver tube mandatory w/p.tube change?

This thread got me thinking.

A few years back – at the time when I had absolutely no idea what was going on inside a tube amp – I (as many other ignorante musicians) solely relied on the wisdom of my local music store.
More than once I’ve seen the shops in-house *tech* pull a tube – look at it – and say:
This tube is reeeaaally bad – better replace it!

Since then I’ve learned a lot – thanks to this board and all the folk here willing to share their knowledge – and, come to think of it, havent’ visited the music store for a long time.

But I’m still trying to learn – so I was wondering:

Are there any reliable visual sign on tubes wearing out at all?
I’m talking output tubes of course – I know preamp tubes can look perfectly new and yet be defective. (Uuuuhh, - so could output tubes, I guees...!)

Trying to find some clues, I looked at a few of my used tubes. I keep them as spares. OK, they all looked used to some degree – and some a little burned due to the heat, but what does one actually have to look for to tell the condition?

And what about preamp tubes?

I’d also like to know if there’s any measurings – apart form using a real tubetester or transcon-something-meter, which I don’t have – that can be done to verify or indicate the condition of a tube?

I’ve discussed some of these thoughts with one of my *clever* freinds, who said:
Put the tube in an amp – if it works the tube is OK, if it doesn’t ...!
Of course he’s right – but I’d like to be able to make a more detailed valuation.

Sorry for the rambling.

Regards
Lion

Replies:

Graywater Lion,You might not ... -- 2/2/2000 11:28 PM