Tube tester for a Predicta 21EAP4

[Eric H]

Originally Posted by charokeeroad

That statement should be true bit it's not. I think just through lazyness when the CRTs were rebuilt the markings weren't updated. I've seen that condition on the last three CRT in a row that I tested. Two of the last three CRTs were marked "21SFA" inside... There is no such tube. The current test proved this CRT to be a very good 6.3V tube.

I don't think 21SFA is a valid number, it probably just means a 21" Short Focus Aperture. 21EAP4 is the original 21" Predicta CRT number. I would go by whatever number is glued to the CRT, not the housing.

The last two Predictas I got had 6.3 volt tubes, I found it out through simple trial and error, if it won't light at 2.3 then go up slowly to 6.3 and see if it does, just don't start at 6.3. They also had stickers saying they had been converted to the 6 volt tube but I wasn't taking any chances.

I also question is 2.35 is the correct voltage? I also see some information that says they are 2.68 volts and my B&K has a 2.68 volt mark on the meter but not a 2.35?