3NP4 testing?
 

Guys, I have a supposedly NIB 3NP4 projection tube I got from that estate in Richmond but I don't know how to test it. I have a CR-70, is there a way to get a meaningful result from that, or am I stuck trying it in an actual Norelco system?

Don't know if this will help?

http://patriotgaming.com/manuals/gam...TT226-4927.pdf

First, you will need jumpers, as it has an odd ball base.

If you need base diagram it is here:

https://frank.pocnet.net/sheets31.html

I'd start by testing it as a 5TP4 which most older CRT testers handled.

In fact, when the 15GP22 first came out, RCA said if the shop did not yet have a color CRT tester use the settings for the 5TP4 for each color and test one color at a time.

I'd like to know your results, as I have two unknown 3NP4's and a NOS 5TP4.

James

Edit: It was just pointed out to me that the above is probably inaccurate, as the only Anode on the 3NP4 is the inside glass coating, while the 5TP4 used both that and a traditional grid anode. Although voltages are similar, the operating method of the two tubes are different. I have no idea of idea the condition of my two 3NP4's.

I tried testing a couple of 3NP4's on a CR-70, setting it up as a scope tube and connecting G2 to pin 3, I was able to get a cutoff setting and an emission reading, but on the low side. I don't know what condition the tubes are in as they were just in a box of loose CRT's. They won't test at all as a 5TP4 or any other "normal" picture tube.

I'd say the best test is in a operating projector.


Chuck

With projection tubes you can guess how good they might be by the amount of phosphor burn, no burn would indicate very low, or no hours. This of course won't tell you if it's gone gassy or has other defects.

Sorry miscopied the link, I doubt this will help much but worth a read perhaps

http://slot-tech.com/interesting_stu...20-%204927.pdf

This one is NIB, no phosphor burn at all. Dag is perfect, so I assume it's new. I only ask because I have no real use for it and would like to sell it, but I got burned in the past with a 5TP4 that supposedly worked for 'a few seconds' then went bad. That tube I was able to test before I shipped it and it had great emissions, so I don't know what happened there. Had to issue a partial refund on it, so avoiding that situation would be great.