7DP4 and the 7JP4
 

"7DP4. This CRT was primarily used in the RCA 621 set. Magnetic deflection; magnetic ... This CRT is electrically identical to the 7JP4 except for the screen size."

Is this true? Can the 7JP4 be substituted for the 7DP4?

Those CRT's are as different as day and night. The gun basic part is probably simular, but that's where it ends. The 7DP4 is simular to the 10BP4. The main difference is the 7DP4 has electrostatic focusing. The 7JP4 has electrostatic deflection, as well as focusing. I picked up a real old Precision CRT tester that will test a 7JP4 and other simular CRT's. It has 6 different tests for that type tube.

Provide a source for that quote--so that it can be corrected.

The 7JP4 is an electrostatic deflection tube in no way compatible with 7DP4 or vice-versa.

My fault. I was reading the snippets that lead in to the website I captured that and pasted it. The actual website doesn't make that claim.

www.myvintagetv.com/picture_tubes.htm


Probably was used to experiment with magnetic deflection. .... 7DP4. This CRT was primarily used in the RCA 621 set. Magnetic deflection; magnetic focus. ... This CRT is electrically identical to the 7JP4 except for the screen size. Electrostatic ...

That site is wrong on the 7DP4:

"This CRT was primarily used in the RCA 621 set.
Magnetic deflection; magnetic focus"

It has Electrostatic Focus, in fact that's the thing that made it hard to rebuild, there were no guns available for it with Electrostatic Focus, all (or most) of the other round tubes, had Magnetic Focus, i.e. 10BP4, 12LP4 etc..

It's fixed, that's what happens when you just cut and paste and don't proof read your own stuff.

Chuck

Oh snap! lol

Oh, it is fixed, is that your Site?

Chuck, what is that gorgeous set in your Avatar? It is not on your site.
*Never mind I found it*

Oops!

Had that been a statement made someplace (not by typo), I'd have been all over it with a great suggestion, such as "the 7DP4 and 7JP4 will also interchange with a 6BG6".

LOL

Charles

A little off topic, but while on the subject of 7" sets: What about the 7Ep4 vs. the 7JP4? I have a friend who still owns the Transvision kit he built in '47, but he threw out the crt years ago after he caught his young children rolling it around the basement floor. He has a spare 7J and would like to use it to get his set rolling again.

I did come across a Transvision that had a 7JP4 installed in it, worked fair.

7JP4 2nd anode is 5 to 6KV, 7EP4 2nd anode is 2KV.
A 7GP4 is a closer match only requires 3KV, but harder to find than 7JP4. Usually found in Philco 48-700 sets.

Better temp tube is a 5BP4, easier to find than either of the others and is electrically identical to the 7EP4

Chuck