Hi everybody.
I'm thinking about building a tube tester, as I can't find any locally.
As I'm just thinking about testing 12ax7 and EL34, and I'm not to fussy about absolute values, I'm only interested in comparing between 2 tubes or at different points in time.
Anybody has schematics? Any pointers would also be welcomed, as my electronics knowledge is limited.
Thanks,
Nuno

If you have a set/s with these tubes just substitute in the circuit. I've known a few guitar players with tube amps who insisted they needed their tube tester(instead of selling it to me) to test their few tubes. So I aggravate them, in fun, and tell them to use that special hearing they have and use their amps as the tester. If you have lots and lots of 12AX7 and 6BQ5 tubes you should get a tester off ebay that will do for what you need.

Bill

:Hi everybody.
:I'm thinking about building a tube tester, as I can't find any locally.
:As I'm just thinking about testing 12ax7 and EL34, and I'm not to fussy about absolute values, I'm only interested in comparing between 2 tubes or at different points in time.
:Anybody has schematics? Any pointers would also be welcomed, as my electronics knowledge is limited.
:Thanks,
:Nuno

:If you have a set/s with these tubes just substitute in the circuit. I've known a few guitar players with tube amps who insisted they needed their tube tester(instead of selling it to me) to test their few tubes. So I aggravate them, in fun, and tell them to use that special hearing they have and use their amps as the tester. If you have lots and lots of 12AX7 and 6BQ5 tubes you should get a tester off ebay that will do for what you need.

Or lots of EL34 which will pay the rent, electric and water bills plus get a nice tube tester.
:
:Bill
:
:
::Hi everybody.
::I'm thinking about building a tube tester, as I can't find any locally.
::As I'm just thinking about testing 12ax7 and EL34, and I'm not to fussy about absolute values, I'm only interested in comparing between 2 tubes or at different points in time.
::Anybody has schematics? Any pointers would also be welcomed, as my electronics knowledge is limited.
::Thanks,
::Nuno

The EICO 625 is a very simple and easy to repair tester. It can often be found on eBay. I like the earlier version with the blue panel. It is supposed to come with a cover and carrying handle, but doesn't always, depending on where it came from (whether it was toted around or kept on a bench or display). If you purchase this tester, replace all resistors if you wish to have accurate results.

This is an emissions tester. It will tell you whether your tubes are weak or strong, which will allow you to determine whether they will give the power you want or not. Using your musical ear can allow you to determine whether the tube in question has the tonal characteristics you desire or not. Tonal characteristics, by the way, usually have nothing to do with whether the tube is good or bad. They have to do with the design of the elements within the tube (spacing, shape, and other characteristics). Power output tubes are most critical of emission. Primary amplifier tubes do not have to be in perfect condition in order to work well. They can easily be weak, and possibly even in the "replace" zone, though not always. Being in the "weak" zone often has no affect on sound, as the current being passed through these tubes is small. Driver tubes, on the other hand, may or may not be affected by strength, depending on how they are wired within the amplifier.

Thomas