Wanted ! 7DP4 B&W CRT - Videokarma.org TV - Video

jhalphen · #1 09-13-2011, 05:28 PM

Hello Gentlemen,

An RCA 621TS TV i purchased at ETF 2011 was recently restored. In spite of all normal CRT electrode voltages and a healthy 7KV EHT, no raster.

The ion trap magnets were photographed to memorize the original position then tweaked in all 4 quadrants: still not the slightest hint of brightness.

I think the CRT is toast, will try to check with a Leader CRT tester/rejuvenator before giving up. I hope it has an adequate connector for this antique.

In the meantime, i am initiating research on a working 7DP4 CRT.

Rare or common?

Recommended substitute? - with or without modifications?

Anyone got an operational tube for sale? - PM please, including shipping cost from USA to Paris/france & payment method (PayPal ?)

Thanks! in advance for any help,

Best Regards

jhalphen
Paris/France

bandersen · #2 09-13-2011, 05:56 PM

Sorry, i don't have one, but I believe a 7TP4 will also work. It's the aluminized version of the 7DP4.

Good luck!

Dave A · #3 09-13-2011, 09:59 PM

PM sent.

***Eric H*** · #4 09-13-2011, 10:02 PM

Are you using the original Elctromagnetic Ion trap?
It's possible it's defective, you can try substituting a standard PM trap.
It requires a double trap same as the 10BP4, the small magnet goes towards the front (or the small coil if it's an Electromagnet)

There is a Military tube that is a perfect sub for the 7DP4, it's aluminized and requires no trap, it's also about an inch shorter and has a different focus voltage, although grounding the focus pin seems to work just fine.

Fair Radio Sales was selling them but a collector bought them all up and was selling them to owners of 621's.

Here's an article on them from the ETF. http://www.earlytelevision.org/7dp4_replacement.html

Here's a link to the guy who has them, don't know if any are left.
http://www.videokarma.org/showthread.php?t=248421