On 09/13/15 13:05, Balekan so wittily quipped:
Well, I had my Triplett 3444 calibrated by Chris Haedt before he passed, God rest his soul. I am now in need of a fresh calibration. Can you folks direct me to who us radio enthusiasts are now trusting with our testers? Any and all help is greatly appreciated!
you've given me an interesting idea...
long ago I had an 'emissions' style tester with the usual 3-position
switches on it, and a big paper roll with all of the switch positions.
I bought it at a swap meet for something cheap. [unfortunately I got
rid of most of my really old test gear for various reasons, "no room"
being a big one].
OK from what I'm reading, on sites like THIS one:
http://www.audiotubes.com/tubetest.htm
there are some really GOOD testers out there that put the device under a
REAL test, not just an emissions test with grids+plate tied together
like a diode. I would guess THAT kind of test might even be bad for the
tube under some conditions, drawing ANY kind of current on G1 being one
of them.
I'm guessing yours is one of those "good ones".
However... if you've got a good tube book handy with the standard curves
in it, a test COULD be devised for the types you typically want to test,
maybe saved in a database or something (pins with voltage levels and
currents), and some 'more modern' device could THEN run the test, under
microprocessor control.
Generating voltages and measuring currents would be trivial things to do
with a microcontroller, given the proper external parts.
It might be a fun project (even if I'm the only one in the world who'd
want something like this).
You'd first do a pin-pin conductivity check, then energize the heater
[testing surge/run current to make sure it's not shorted or damaged],
let the tube warm up, then apply test voltages in a reasonable order,
and measure the resulting cathode current.
Something like that is relatively easy for a microcontroller [been
there, done that], again with the proper external parts. Even something
simple like an Arduino could do it.
Biggest problems would be testing larger tubes like KT88 (or something
similar) since the max current on those is ~400ma (0V g1, 300V g2, 66V
plate, I checked the operating curves).
Anyway this is just a mental exercise at the moment. But it might cost
less to build (in parts, not time) than what the guy on that web site I
mentioned above is asking for HIS tube testers ($500 or so each I guess)
it might also be useful to find (or verify) 'matched pairs'. or print
up the actual operating curves.
[some time ago I saw a web page where someone made his own tubes,
hand-blown glass and everything - it was on a video. He did curve
testing afterwards to verify the operating characteristics, with
professional gear, probably expensive]