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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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24th Jun 2005, 1:03 pm | #1 |
Octode
Join Date: Jan 2003
Location: Birmingham, West Midlands, UK.
Posts: 1,268
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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 |
Heptode
Join Date: Jul 2003
Location: North Walsham, Norfolk, UK.
Posts: 516
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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 |
1st Jul 2005, 11:54 pm | #3 | |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,274
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Re: Substituting different CRT's
Quote:
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. |
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2nd Jul 2005, 1:24 pm | #4 |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,274
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Re: Substituting different CRT's
I've just reduced the image sizes.
Peter. Last edited by Mike Phelan; 18th Jun 2007 at 12:05 pm. Reason: Tidy up for archiving |
7th Jul 2005, 7:33 pm | #5 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,147
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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, 12:31 pm | #6 | |
Octode
Join Date: Jan 2003
Location: Birmingham, West Midlands, UK.
Posts: 1,268
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Re: Substituting different CRT's
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:
TTFN, Jon |
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11th Jul 2005, 3:09 pm | #7 | |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,274
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Re: Substituting different CRT's
Quote:
Peter. |
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11th Jul 2005, 3:10 pm | #8 |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,274
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Re: Substituting different CRT's
And the rest...
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