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Need advice on tubes and testing


jimjimbo

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Picked up a pretty old what looks like a PA/music amp that a guy had gotten out of a local dance hall some years ago.  Loaded with tubes.  Gave him $20 bucks for it, and raced back here....No idea if any of them are good, but would like to find out.  Questions?  Should I invest (modestly) in a tube tester?  (I have other tube amps that I am using), or, can I take them somewhere to have them tested?  Do RadioShack do this?, or, other advice? (send them off somewhere?)

 

A couple of them don't look so great, but most are in good shape.  Here's the list: (with quantities)

 

Sylvania 6SN7 GTB (5)

GE 6SN7 GTA (2)

Sylvania 6SL7 GT (1)

Philco 6SN7 GTB (1)

Raytheon 6K6 GT (1)

RCA 6C5 (1)

Unknown 6AU6 (6)

 

Admiral 6V6GT (1)

National Union (NU) 6V6 GT (1)

GE 6X5 GT (1)

Unknown 12AU7 (2)

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I was a licensed TV repairman in the 70's when everything had tubes in it. I have used quite a few tube testers and they are not that reliable as far as trying to pinpoint a problem.

 

They will always tell you if a tube is shorted, open or completely fried but will often show tubes that are just out of spec as good. 

 

The best way to test a tube is to replace it and see if the circuit works.

 

My point is don't expect a miracle machine.

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The only real way to know if a tube is good is to evaluate its performance in the circuit in which it will be used.  Even the tubes which you say don't look so good may be just fine.  Do you have a brand and model for this amp?  That would be helpful in determining if it would be suitable for hi-fi applications and whether having it restored would be worth the expense.

 

Maynard

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The amp chassis is of no concern.  I was looking for how/where to get tubes tested, in order to evaluate their relative value.  I have no use for any of the tubes mentioned, so I would like to sell them to someone who could use them if they are worthwhile, that's it....

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