7" electrostatic question
 

I have a working 7" set that uses a 7jp4. If I wanted to test a 7jp4 in another set is it ok if I set them back to back and put the socket from the working one to the one in the set I want to test. Sorry if this is a dumb question, just want to make sure I'm not overlooking something. Thanks.

You're fine to do this. Just be gentle when you spin the socket around and over to plug in to the other set. (Brittle insulation could be an issue, otherwise usually fine to do this.)

Yes, that's how I did it with two Motorola VT-71 sets, and as stated by NoPegs, just be very careful with the sockets and you won't have a problem. CRT testers that do 7JP4s are like hen's teeth.
Good Luck! :D
Kevin

I bought an old Precision CRT tester, just for that purpose. It only tests, no rejuvenation. On the roll chart, it only lists a 7JP1, but it works fine for the P4. I don't know why it don't list a 7JP4, as it's only a phospher difference. :boring:

Realistically I think you can more or less just do some rats-nest wiring to an octal plug and some micro-grabber clips, and just use a "normal" tube tester. I'm fairly certain that it would at least do shorts/emissions with some level of efficacy.

And you base this on what?

Based on how my Accurate Instrument Co. Model 257 works if you want to "test" a CRT...


Here's the relevant manual pages for your perusal. (Linked due to size.)


http://www.funkengine.net/vk-img/2015-01-28/CRT-1.png
http://www.funkengine.net/vk-img/2015-01-28/CRT-2.png


Providing you know which pin is which position on the selector switches, and what pin of the tube you've connected it to, you should be able to at least go/no-go a tube in the field...

Armed with the data charts for my EICO-666, and a homebrew adapter, I think I could possibly come up with something that goes a bit further than toast or not-toast. The EICO-666 can actually come close to the appropriate voltages required for a real test of a CRT, the Accurate Instruments Co. 257, not so much. (That's why it says use the "DIODES OK" scale.)

Get back to us after you have actually tested one.

What John means is most testers fail to produce a result with the 7JP4, my CR-70 for example shows no emission even on a known good tube.