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RikstoneAmps wrote:
Tube tester for EL34, EL84 and 12AX7 (ECC83)
This is a simple tube tester which is based on a schematic published
in the middle 50's in a Polish radio amateur magazine.
You cannot reach 100% test coverage with this tester. Actually there are only
two different test cases you can perform. One of them is the check of anode
current when changing grid voltage. When grid voltage is set to same potential
with the cathode by using the "control switch" the anode current should remarkably
increase. Another test you can do is the check of the heater current. Note that in
both tests a separate current measurement instrument is needed.
The schematic is generic which means you can quite easy add many type of tubes to it.
Before you add any other tubes make sure that all the pins such as anode cathode
grids and heaters will be correctly connected. A good reference for that is the current
schematic and data sheets of the tubes.
The main component of the tester is power transformer that shall fulfill the requirements
of the tubes you are going to test. E.g. in case of the EL34 tube the heater current can
shortly exceed 2A. In order to protect the transformer three fuses have been added
to the schematic.
