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#1
08-02-2008, 10:05 AM
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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 
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#2
08-04-2008, 12:11 PM
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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.
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