Hi All

I had always been under the impression that a 12KP4 tube did not require an ion trap. Yet today, I was looking at the descriptions for the 12KP4 and 12KP4A, and correct me if I am wrong, but is it only the 12KP4A that does not require an ion trap.

12KP4 description, states "prevents ion spot blemishes" which makes me wonder if it means it still used an ion trap
http://tubedata.milbert.com/sheets/093/1/12KP4.pdf


12KP4A description states "does not require an external ion trap magnet"
http://tubedata.milbert.com/sheets/093/1/12KP4A.pdf


Pardon my ignorance, but am wondering if there is any difference between a 12KP4 vs 12KP4A

thanks

Ross

The 12KP4A has a gray faceplate.

You left a key part out the 12KP4 description "...a reflective metal-backed screen which prevents ion spot blemishes..." That's the aluminized coating that prevents the ion spots.

That being said, I've read mixed reports about the 12KP4 using an ion trap.

All I can say for sure is that have an unmarked aluminized CRT the seller claimed was a 12KP4 and it definitely needs a single pole ion trap magnet to function.

Thanks Bob

Just wondered, as if the12KP4 and 4A are the same and both have an aluminum coating and neither one required an ion trap, then why the different names P4 vs P4A

Strange.

I just found another thread which goes into detail KP4 vs KP4A, post at very bottom


http://www.videokarma.org/showthread.php?p=3065780

It's been my experience that most round B&W CRTs that end with A or B have a tinted or frosted faceplate. Like the 10BP4A/B, 16GP4B/C, 19AP4A/B, etc.

I just found another thread which goes into detail KP4 vs KP4A, post at very bottom


http://www.videokarma.org/showthread.php?p=3065780

BTW: In case you don't know here is some trivia on CRT numbering. The P# digits (IE P1, P4, P22, etc) indicate phosphor color...P1 being green P4 being white, P22 being a full color tri-phosphor CRT.
The first numbers are diagonal CRT face size in inches, but in ~1967-68 it changed to viewable screen area diagonal. The letters before the P I believe are arbitrary unique-to-the-type identifiers and suffixes past the P# usually indicate slightly 'improved' compatible versions.

Ross, Never hesitate to ask about anything related to the forum. The folks here want to help others, and have helped me many times. THANKS!
Interesting about the 12 inch CRT's and their various specs. I guess that 12LP4 is most common, and the 12K, and 12Q aren't too far behind. I only have 3 sets with 12 inch CRTs, 1950 Philco, Dumont Doghouse, and a Stromberg-Carlson TS-125 chassis (40 tube version) that I just picked up, with a 12QP4 that uses an ion trap.
Been "playing" with TVs for 50 years, and hope to go another 50 LOL.
Best Wishes,
Kevin

Thanks Kevin. I find it can be a little intimidating starting a thread on here as I don't want to sound like a fool, as everyone is so knowledgeable on here, but unless I ask, I'll never know!!

Thanks Kevin. I find it can be a little intimidating starting a thread on here as I don't want to sound like a fool, as everyone is so knowledgeable on here, but unless I ask, I'll never know!!

I have asked the most foolish of questions you can imagine on this forum :screwy: and have always been met with wonderfully helpful answers instead of sarcasm. The incredibly helpful people on this forum is one of the main reasons I love with hobby so much.