Charlton TV Tubes

[murphyv310]

Hi.

Has anyone ever come across a Re-Gun CRT by the name of "Charlton Television Tubes"?
I have come across on in a Pye VT4, I'd like to find out where the CRT was re-gunned.

[FERNSEH]

"Charlton Television Tubes" Hi Trevor, that's one tube rebuilder I not familiar with. Interesting to note the set has an electrostatic focus CRT.
It's possible late production Pye VT4 sets were equipped with this type of tube.

DFWB.

[Heatercathodeshort]

That is interesting David. What makes you think it has an electrostatic focus gun? I have never seen a VT4 with this type of tube including the late CTM4.
I have never come across a CHARLTON tube. I wonder where the VT4 came from. John.

PS Just seen the shift on the back of the scan coils. Very odd.

[murphyv310]

Hi John.
It's my set, it's a re gun and the focus magnets are removed. The LOPT is faulty and I've substituted a Thorn 1500 jelly pot. It works but needs a little further modification to be 100%

[Heatercathodeshort]

Aghh so that is the answer. The tube was probably sourced locally to the V4 back in it's day. Something tells me it looks a good one but I will probably be shot down in flames!
John.

[mark pirate]

There were many tube rebuilders back in the day, I have two sets with regunned CRT's, Re-veiw & Lawson, both are still going strong.

It is a real shame that all the equipment used was never saved, I am sure there would be a steady demand for rebuilds now.


Mark

[murphyv310]

Hi.
It's a really good tube John, even with 190v AC from the variac it's bright with pin sharp focus, the EHT Is a bit high from the jelly pot above 190v also the width is a bit short, so the transformer needs some tuning to reduce EHT and give more width. Once done and the work is tidy I'll take some pictures of what I've done and the results.

[murphyv310]

Originally Posted by mark pirate

There were many tube rebuilders back in the day, I have two sets with regunned CRT's, Re-veiw & Lawson, both are still going strong.

It is a real shame that all the equipment used was never saved, I am sure there would be a steady demand for rebuilds now.


Mark

Admittedly there would be some work but not enough to run a full time business Mark.
The issue is these days going green, CRTs are far from efficient re light output vs power consumption plus of course their bulky. Once the collectors got their tubes done work could dry up and remember RACS? They were far from cheap.

[FERNSEH]

The attachment shows the scanning components on the electrostatic focus CRT installed in a Pye CTM4.
It's possible late VT4 sets are similar.

DFWB.

[Heatercathodeshort]

That is interesting David. I must admit the last time I serviced a CTM4 was probably around 1964! It would be interesting to discover an original VT4 with the AW36-21 electrostatic focus tube.

Pye tended to be the last company to employ MFTs. They used the MW43-80 tube in quite a few CTM series 17" models when everyone else was using the AW43-80 EFT.

Thinking about it I wonder why Mullard produced a magnetic 90 degree tube? John.

[mark pirate]

Once the collectors got their tubes done work could dry up and remember RACS? They were far from cheap.

Fair point Trevor, maybe time to build a time machine to go back to the 50's.
There were plenty available in Practical Television adverts.

These days I just keep looking out for rough donor sets on ebay....


Mark

[FERNSEH]

hi John,
was Pye the only manufacturer to use the MW43-80?
Can't recollect any other TV firm ever using the tube.
The Radiomuseum informs us the developer was Mullard so it's possible the tube was made at the behest of Pye Ltd.

https://www.radiomuseum.org/tubes/tube_mw43-80.html

The AW36-21: https://www.radiomuseum.org/tubes/tube_aw36-21.html First application in late 1955 and in common use the following year.

DFWB.

[slidertogrid]

Is it Ok now to post links to RM? Because when I did the link was removed and I was told that RM are protective of their information and I could could get banned for posting? (I had checked the info wasn't available from Paul's diagram site first).
Or does it "Depend" ?

[Nuvistor]

As far as I am aware you can post links ( if the circuit it not available on this site) but not the circuit diagrams RM allow you to download.

[murphyv310]

Hi
To add to the modification to the VT4 I have now got a full size scan and the EHT is now correct. The issue though it the feedback from the Jellypot to the existing circuit. With over 300v P-P from the transformer its far too high for the subsequent transformer in the Pye, I dont see a way of getting round this as a resistor network is no use as the waveform is the wrong shape, I also tried a suitable line blocking osc transformer to step down the high output which had the ratios just about spot on but it was saturated by the high level from the jellypot. I wonder if series caps would work but of course the phase will be out so the APC may not function correctly and I could land up with a false lock on the line TB, or would I?

[slidertogrid]

Wouldn't it be simpler to get the original Transformer rewound ? Or is it a type that's not possible? I am not familiar with the design of the original LOPT these sets were a little before my time...

[FERNSEH]

The VT4 line output transformer can be rewound but expect to pay >£100 to have it done. Might be cheaper just have the primary rewound and use a tripler for the EHT.

DFWB.

[Cobaltblue]

Posts about the Jellypot Mod moved to a New thread here.

https://www.vintage-radio.net/forum/...d.php?t=178543

Cheers

Mike T

[murphyv310]

Thanks very much Mike

[murphyv310]

Hi.
Although this is a very good CRT I think that the process may have been rushed. There is a number of Phosphors missing, you don't see the issue when the set is running and on the VT4 with It's dark perspex implosion screen they cannot be seen. When I cleaned the screen today it was obvious that they were missing.
The photo is not that clear TBH.