#1
|
|||
|
|||
20DP4 and 20CP4 are they interchangable
I have a Philco console (cir. 1953) that uses either a 20CP4 or 20DP4. Number is missing on the old CRT, and Sams lists both, along with a 21 inch tube that I found out doesn't fit. Are they interchangeable? If you have either one for sale that has good emission, also let me know.
|
#2
|
||||
|
||||
I briefly compared the datasheet and they look pretty darn similar. Same pinout, deflection angle, single field ion trap etc. Similar voltages and dimensions.
http://frank.pocnet.net/sheets/127/2/20CP4.pdf http://frank.pocnet.net/sheets/127/2/20DP4.pdf |
#3
|
|||
|
|||
Quote:
I expect the "differences" were likely just slightly different versions of essentially the same thing with minor variations being "invented" at different companies and thus being registered separately with the RTMA. In Peter A. Keller's "The Cathode Ray Tube: Technology, History and Applications" (1991) pp.158-160, he notes: Quote:
Last edited by drussell; 09-22-2014 at 11:26 AM. Reason: Added 3rd paragraph to quote |
#4
|
|||
|
|||
CRT interchangability!
I always understood that was the slight differences in numbering codes was the manufacturers practice to differentiate their product, from the other makes.
Didn't all those CRT designs, have to be registered with the RMA or RETMA, at the time? BTW,I never ran across, any of those CRT's listed in the text, like the 20" numbers. |
#5
|
|||
|
|||
Quote:
I really can't say enough good things about this book... I have not checked but copies may still be available directly from Mr. Keller at <kellerp4(at)frontier(dot)com>. Quoting once again, this time section 1.10, "CRT and Phosphor Nomenclature", pp. 41-2: Quote:
That's not surprising. The 20s are quite rare as the 21s became the popular size and were manufactured in much greater numbers, hence the reason the SAMs for this TV lists the two 20-inch tubes (presumably they essentially used whatever they could source on the early models) and then the 21-inch version as they became more popular which would have required slight alterations to the faceplate and mounting but otherwise would likely be essentially the same chassis and cabinet. Last edited by drussell; 09-22-2014 at 12:43 PM. |
Audiokarma |
#6
|
|||
|
|||
Sounds like either one will work, so now I am looking for one that I can put into the Philco that I'm restoring. Set has been recapped, works ok otherwise, except the CRT went so dark, that one can barely see the picture. Emission is almost zero on the original tube. I got the Sams and ordered and paid $125 for a 21EP4, (which I have now posted for sale), as the Sams listed that as the replacement on the schematic, not realizing that some models used the 20 inch tube. Took out the old tube, found the NOS 21EP4 wouldn't fit. Now, I am in need of the 20DP4 or 20CP4. I thought I could retro-fit the 21 inch tube in it, but it won't fit the face plate, mounting corners would have to be cut out and redone, and then the straps that hold the yoke and magnet assembly are too short. Other words the 21 inch just won't work in it. Thanks everyone for you help. If anyone has one of these tubes that is usable, or would like to trade the your 20 inch tube for my 21 inch, let me know.
|
#7
|
|||
|
|||
Quote:
|
#8
|
||||
|
||||
I had a Magnavox once whose CRT was labelled as 20CP4/20DP4. It was a rebuild so I'd gather they were close enough to interchange.
|
#9
|
|||
|
|||
Once again thanks for all the info, don't know if I will be able to find a reasonable and good 20CP4 or 20DP4 for it, but one never knows. I guess it's pretty rare.
|
|
|