Substituting different CRT's - UK Vintage Radio Repair and Restoration Discussion Forum

Duke_Nukem · 24th Jun 2005, 1:03 pm

Someone else and myself are thinking of producing a, er, "ultimate" guide to CRT substitution. OK, there are a number of manufacturers books that give some substitutions (mainly Mullard) but does anyone else have further info ?

So, firstly does anyone have any manufacturer's info for the ""lesser"" brands ? Also, if anyone has done substitutions we would be interested to know if it was litterally a straight swap, or whether the mechanics had to be adjusted, diff scan coils, any circuit mods, etc.

its no suprise that there no manufacturer info to show how to replace, say, a Mazda with a Mullard. And I've not seen anything for Ferranti, GEC, HMV, etc. Again, if anyone has tried more unusual swaps then we'd like to know. For example I have a GEC set and that has a Ferranti tube, Practical Telly mag also gave details of how to swap a metal cone tube for a later rectangular type, and I've been told that the tube out of an Ekco TMB272 can be used in a TV22 ?

Anyhow, particularly interested if people have done these subsitutions and any problems that needed to be sorted in doing it.

TTFN,
Jon

Danny · 28th Jun 2005, 10:51 pm

Hi
I've found that most tubes can be swapped about but some have fatter necks, i e GEC; also some focus magnets are of a diffrent gauss so need to be moved back: sometimes this is not practical.
It's mainly the mechanics that cause problems i e if the tube has a shorter bulb then the tube might not fit in the cradle.

Heater supplies can cause problems. I got a new old stock GEC tube for my 2147 and its heater didn't light (gulp) but when ran from a heater tranny it did.
I checked the current and it was .5 even but my book states .3 for that tube.
Also heater voltages vary.

peter_scott · 1st Jul 2005, 11:54 pm

Quote:

Originally Posted by Duke_Nukem

Someone else and myself are thinking of producing a, er, "ultimate" guide to CRT substitution. OK, there are a number of manufacturers books that give some substitutions (mainly Mullard) but does anyone else have further info ?

TTFN,
Jon

Hi Jon,

I have a little Edswan-Mazda guide from 1953/54 if it would be useful.
It gives their suggested bottles for a range of sets. see example attached.

Peter.

peter_scott · 2nd Jul 2005, 1:24 pm

I've just reduced the image sizes.

Peter.

Heatercathodeshort · 7th Jul 2005, 7:33 pm

Most picture tubes can be made to work to a satisfactory degree in our vintage receivers. It may be necessary to add a small heater transformer, change the tube base connector and maybe wire up a second anode supply from the H.T. or boost H.T. supply. Following these simple changes you will have a 99% chance of obtaining a good picture.
2 voltTriodes typically MAZDA [CRM92 CRM121B etc] can be replaced by the Mullard 9" range with little to modify. Triodes require a higher focusing field than a tetrode but shunts fitted across the focus magnet will solve this. The rule is simple, if it fits from a physical aspect I.E. screen size, NECK SIZE [check the scan coils will slide over] approximate scanning angle and neck length and you can deal with the heater voltage and current, stick it in! Remember its the heater CURRENT not voltage that is important in series heater chains. Don't worry too much if the EHT voltage does not match the replacement tube. A few KV either way is of little importance. What I have said might surprise some members but I assure you I speak with a good guarantee! The problem of course is the early electrostatics but I doubt if that would bother many. Another difficult series were the early PYREX EMI tubes used in the pre war models and a few odd balls from the post war E.M.I. era. Other than that you should not encounter any problems. The DEFIENT sets using the PLESSEY MK1 chassis [1952] were designed to use any 12" tube that was available and had taps on the mains transformer to allow for this. As always drop me a note if you want any advice. JOHN.

Duke_Nukem · 11th Jul 2005, 12:31 pm

Hi all,

Whilst many CRT's can be adapted to a set, what I'm particularly after is some real details of swaps that have been tried. For example, how well did the mask fit ? Were any electrical mods required ? That kind of thing.

Donkeys years ago I guess you could pick up the odd tube lying around the workshop and "bung it in" to see how well it fitted. However these days if you need to swap a tube then most people will have to specifically go out and buy a tube, hence the desire to get a list of actual known swaps that are known to work.

Quote:

I have a little Edswan-Mazda guide from 1953/54 if it would be useful.

Thanks Peter, looks useful. CRT details are nice, however I also notice the sample page includes some manufacture's telly models that I wasn't aware of so yes, I would be interested in the rest.

TTFN,
Jon

peter_scott · 11th Jul 2005, 3:09 pm

Quote:

Originally Posted by Duke_Nukem

Hi all,

Thanks Peter, looks useful. CRT details are nice, however I also notice the sample page includes some manufacture's telly models that I wasn't aware of so yes, I would be interested in the rest.

TTFN,
Jon

I'm not sure at what file size the forum censors me. I'll try sticking them all on this post and if that fails I'll try and spread them over a number.

Peter.

peter_scott · 11th Jul 2005, 3:10 pm

And the rest...

24th Jun 2005, 1:03 pm	#1
Duke_Nukem Octode Join Date: Jan 2003 Location: Birmingham, West Midlands, UK. Posts: 1,268	Substituting different CRT's Someone else and myself are thinking of producing a, er, "ultimate" guide to CRT substitution. OK, there are a number of manufacturers books that give some substitutions (mainly Mullard) but does anyone else have further info ? So, firstly does anyone have any manufacturer's info for the ""lesser"" brands ? Also, if anyone has done substitutions we would be interested to know if it was litterally a straight swap, or whether the mechanics had to be adjusted, diff scan coils, any circuit mods, etc. its no suprise that there no manufacturer info to show how to replace, say, a Mazda with a Mullard. And I've not seen anything for Ferranti, GEC, HMV, etc. Again, if anyone has tried more unusual swaps then we'd like to know. For example I have a GEC set and that has a Ferranti tube, Practical Telly mag also gave details of how to swap a metal cone tube for a later rectangular type, and I've been told that the tube out of an Ekco TMB272 can be used in a TV22 ? Anyhow, particularly interested if people have done these subsitutions and any problems that needed to be sorted in doing it. TTFN, Jon

28th Jun 2005, 10:51 pm	#2
Danny Heptode Join Date: Jul 2003 Location: North Walsham, Norfolk, UK. Posts: 516	Re: Substituting different CRT's Hi I've found that most tubes can be swapped about but some have fatter necks, i e GEC; also some focus magnets are of a diffrent gauss so need to be moved back: sometimes this is not practical. It's mainly the mechanics that cause problems i e if the tube has a shorter bulb then the tube might not fit in the cradle. Heater supplies can cause problems. I got a new old stock GEC tube for my 2147 and its heater didn't light (gulp) but when ran from a heater tranny it did. I checked the current and it was .5 even but my book states .3 for that tube. Also heater voltages vary. Last edited by Mike Phelan; 18th Jun 2007 at 12:07 pm. Reason: Tidy up for archiving

2nd Jul 2005, 1:24 pm	#4
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: Substituting different CRT's I've just reduced the image sizes. Peter. Attached Thumbnails Last edited by Mike Phelan; 18th Jun 2007 at 12:05 pm. Reason: Tidy up for archiving

7th Jul 2005, 7:33 pm	#5
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Substituting different CRT's Most picture tubes can be made to work to a satisfactory degree in our vintage receivers. It may be necessary to add a small heater transformer, change the tube base connector and maybe wire up a second anode supply from the H.T. or boost H.T. supply. Following these simple changes you will have a 99% chance of obtaining a good picture. 2 voltTriodes typically MAZDA [CRM92 CRM121B etc] can be replaced by the Mullard 9" range with little to modify. Triodes require a higher focusing field than a tetrode but shunts fitted across the focus magnet will solve this. The rule is simple, if it fits from a physical aspect I.E. screen size, NECK SIZE [check the scan coils will slide over] approximate scanning angle and neck length and you can deal with the heater voltage and current, stick it in! Remember its the heater CURRENT not voltage that is important in series heater chains. Don't worry too much if the EHT voltage does not match the replacement tube. A few KV either way is of little importance. What I have said might surprise some members but I assure you I speak with a good guarantee! The problem of course is the early electrostatics but I doubt if that would bother many. Another difficult series were the early PYREX EMI tubes used in the pre war models and a few odd balls from the post war E.M.I. era. Other than that you should not encounter any problems. The DEFIENT sets using the PLESSEY MK1 chassis [1952] were designed to use any 12" tube that was available and had taps on the mains transformer to allow for this. As always drop me a note if you want any advice. JOHN. Last edited by Heatercathodeshort; 7th Jul 2005 at 7:38 pm.

11th Jul 2005, 3:10 pm	#8
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: Substituting different CRT's And the rest... Attached Thumbnails