Testing an old scope CRT
 

Hi All
I have a 3AP1/908-A to test & was wondering since that CRT has the heater & cathode connected together, will it test properly on my Heathkit IT-5230 CRT tester? I get the short lamp and the emission instantly goes to 6 without the normal slow warm-up rise & the cutoff control takes it to 1 when at minimum. I put a load resister across the filament to track it better for the needed 2.5V filament voltage.
Thanks in advance for anyone's 2 cents.
Danny in Cleveland

You might wire a floating external power supply to the heater in order to perform
the test. The tester may want to see some kind of load on its own filament leads,
but I guess you could achieve proper test results this way. A heater to cathode
short is normal when testing such a tube.

Of course, performing a rejuvenation would not be possible with this trick, but
is it feasible anyway? Good luck.