How to test a crt, without a tester?

[jbivy]

Please forgive my ignorance here, im just getting into these. With radios, im mediocre, but tv's are still complete magic to me.

I figured id start the recapping on my 1950 motorola this month. Picked up a sams photofact for it already. But if the crt is dead..well..

I read on here and now cant find it, a simple test for seeing if theres at least some life left in your crt. It was akin to hooking a 6 volt battery up to say pin one and six, seeing if it lights up.

If anyone can help me out here, id be really appreciative.

and if it fails well.. i guess ive a nice cabinet and rust free chassis for free then.

[ctc17]

That will only tell you if the filament in the crt is good, chances are it is. Usually when crts fail its due to low/no emissions.
I would recommend investing in a crt tester, you can pick them up off ebay for almost nothing. It could save you a ton of time.
What is the crt number?

[jbivy]

well its a 12LP4A.

Since all these crt testers are so old, wouldnt they be suffering from the same problems that many old electronics have? Circuitry going or already gone out?

[bandersen]

True, but there's not much to the early models really. Maybe just a couple of capacitors to replace and controls to clean.

Here's the pinput for a 12LP4: http://www.bunkerofdoom.com/tubes/sy...crts/12LP4.jpg

The filament is between pins 1 and 12. That's either side of the key on the base. Check for continuity between those pins. It should be a very low resistance.


P.S.
I'll haul my Motorola chassis out in a few days and we can compare notes.