[sdiy] A simple 12AX7 vacuum tube tester schematic..

[Paul Perry]

A very much simpler solution, is to increase the sensitivity of the current
meter, by switching the shunt across the meter.

(note the shunt may be INSIDE the meter).

Paul perry Melbourne Australia
(doing everything the easiest correct way)

-----Original Message-----
I need a simple schematic for a tester 
of the popular ECC83/12AX7 vacuum tube
used in lots of audio/musical amplifier
these days. I already have 2 tube testers
but because this type of tube draws very little
plate current my testers meter's needle 
doesn't go up very far so readings are
not quite acurates.

All I need is a component list of the best values for
a standard triode tube circuit section that would have:

The VDC supply value for the test schema (ex: 350VDC)
The plate resistor
The cathode resistor (if any needed) to the ground
The grid resistor value (to the ground ?)
The negative bias test voltage (ex: -1.3v)
The uAmp meter value for readings (hooked in series with the plate
resistor)(ex: 0-100uA)
The threshold meter reading value for a GOOD ECC83/12AX7 (ex: 60uAmp
or more is GOOD)

A simple SPDT switch will select what section of the tube is tested.

Thanks
JP