Valve test, final year project?

[Mickpc]

I am currently going over the concept of doing a valve tester as a final year project (EE), it would be microprocessor controlled and I would hope that it would give a reliable indication of the life left in a tube.
Do you guys/gals have any feedback on this?

Thank you Mick Carey

 

[chuckey]

Do you mean CRT or thermionic valve? With a CRT you could measure the light output when in use, this is a very good test especially on colour CRTs, where the blue* gun always fails first ( you get a colour cast as the tube ages). If you are talking about thermionic valves, then you have to estimate the reservoir of emission left in the cathode. The classic way would be to increase the filament voltage to see how much the Ia increase, unfortunately this will see off an old valve. I wonder if reducing it will reduce the Ia depending on how high up the knee it is operating.
* blue? , I am having second thoughts, it might not be! - Its 30 years + since I fiddled with CRTs, but a colour cast is a definite sign, providing the set's gun controls have not be fiddled with.
Frank

 

[betwixt]

Estimating remaining life would be difficult but testing characteristics should be fairly easy. You need a variable positive supply for the anode (plate) and a variable negative supply for the control grid. Use the micro to measure the anode (or cathode) current as the grid voltage is varied and to measure the current with constant control grid voltage while changing the anode voltage.

Brian.

 

[schmitt trigger]

Since different valves (tubes) have different pinouts, heater voltages, plate currents, grid cutoffs and other parameters (including triode vs pentode curves) my question to you would be:

-is this project for a single valve type (like an ECC83/12AX7) or do you want to test multiple valve types?

 

[schmitt trigger]

Another example of the single post user, which creates an account to ask a question, and is never heard from again.