Conversion of the HMV 904 to use a 5F4 CRT - UK Vintage Radio Repair and Restoration Discussion Forum

Paul Stenning · 27th Feb 2006, 11:34 pm

I have just received the attached PDF document from Hugo Holden who feels it will be of interest to some of you and asked for it to be posted here.

Steve_McVoy · 28th Feb 2006, 12:25 am

5FP4s are relatively hard to find. Another tube that works well is the 5AXP4, which was the first universal test tube made in the U.S. They are easy to find and physically very similar to the 5FP4.

I used one of them to replace the CRT in our Pye 817 when the Emiscope 3/1 (not the original tube) that came with the set failed:

http://www.earlytelevision.org/pye_817.html

ppppenguin · 28th Feb 2006, 9:04 am

Thanks for this valuable information. I have a Marconiphone 706 (= HMV 904) and thankfully the CRT is still usable. It's far from perfect but I see no reason (yet) to make the set non-original just to get rid of the ion burn and get a bit more brightness. It might be worth acquiring a 5AXP4 against the day that my CRT fails.

28th Feb 2006, 12:25 am	#2
Steve_McVoy Pentode Join Date: Feb 2004 Location: Columbus, Ohio, USA Posts: 150	Re: Conversion of the HMV 904 to use a 5F4 CRT 5FP4s are relatively hard to find. Another tube that works well is the 5AXP4, which was the first universal test tube made in the U.S. They are easy to find and physically very similar to the 5FP4. I used one of them to replace the CRT in our Pye 817 when the Emiscope 3/1 (not the original tube) that came with the set failed: http://www.earlytelevision.org/pye_817.html

28th Feb 2006, 9:04 am	#3
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: Conversion of the HMV 904 to use a 5F4 CRT Thanks for this valuable information. I have a Marconiphone 706 (= HMV 904) and thankfully the CRT is still usable. It's far from perfect but I see no reason (yet) to make the set non-original just to get rid of the ion burn and get a bit more brightness. It might be worth acquiring a 5AXP4 against the day that my CRT fails.