P4 or P45 phosphor? - UK Vintage Radio Repair and Restoration Discussion Forum

Panrock · 3rd Dec 2013, 7:05 pm

Hi, I'm currently involved, along with a customer, in having a CRM121 tube rebuilt in America. This may be the first of many if the trial proves successful.

The company has been asking whether we prefer a P4 or a P45 phosphor, but as yet they haven't been able to tell us the difference! Both are short-persistence white.

There's a useful article on phosphors at http://en.wikipedia.org/wiki/Phosphors . From this, it seems the P4 exhibits a twin (or broad) peak at 565 and 540 nM; the P45 has one peak at 545 nM. The P45 was allegedly used in 'viewfinders'.

We would prefer a 'cold' white if possible. Does anybody know what is the subjective difference to the eye between P4 and P45 ?

Thanks!

Steve

Barry Lloyd · 3rd Dec 2013, 7:44 pm

The one that goes to 565 (shorter wavelength) might be more bluish = more cold? Just a guess!

You might find this article interesting in that it gives typical uses for the different phosphors:
http://en.wikipedia.org/wiki/Phosphor

Barry

Brigham · 4th Dec 2013, 10:55 am

Interesting! I wonder what the red phosphor was in pre-1964 CRTs?

I'm hoping that a co-ordinated rebuilding service can be developed for obsolete tubes; lack of replacements is becoming an obstacle within the hobby. I still strongly suspect that the capacity already exists in China.

3rd Dec 2013, 7:05 pm	#1
Panrock Nonode Join Date: Feb 2005 Location: Worcestershire, UK. Posts: 2,534	P4 or P45 phosphor? Hi, I'm currently involved, along with a customer, in having a CRM121 tube rebuilt in America. This may be the first of many if the trial proves successful. The company has been asking whether we prefer a P4 or a P45 phosphor, but as yet they haven't been able to tell us the difference! Both are short-persistence white. There's a useful article on phosphors at http://en.wikipedia.org/wiki/Phosphors . From this, it seems the P4 exhibits a twin (or broad) peak at 565 and 540 nM; the P45 has one peak at 545 nM. The P45 was allegedly used in 'viewfinders'. We would prefer a 'cold' white if possible. Does anybody know what is the subjective difference to the eye between P4 and P45 ? Thanks! Steve __________________ https://www.radiocraft.co.uk

3rd Dec 2013, 7:44 pm	#2
Barry Lloyd Retired Dormant Member Join Date: May 2006 Location: London, UK. Posts: 129	Re: P4 or P45 phosphor? The one that goes to 565 (shorter wavelength) might be more bluish = more cold? Just a guess! You might find this article interesting in that it gives typical uses for the different phosphors: http://en.wikipedia.org/wiki/Phosphor Barry

4th Dec 2013, 10:55 am	#3
Brigham Octode Join Date: Mar 2006 Location: Co. Durham, UK. Posts: 1,117	Re: P4 or P45 phosphor? Interesting! I wonder what the red phosphor was in pre-1964 CRTs? I'm hoping that a co-ordinated rebuilding service can be developed for obsolete tubes; lack of replacements is becoming an obstacle within the hobby. I still strongly suspect that the capacity already exists in China.