BUSH TV63 strange CRT phenomenon. - UK Vintage Radio Repair and Restoration Discussion Forum

Heatercathodeshort · 17th Oct 2009, 11:37 am

Last night I spent a couple of hours pumping life back into this 14" Bush table model TV63. Another Forum member has a fault on the receiver unit of his console version and rather than struggle with the huge cabinet on the bench decided to use the TV63 as a 'test rig' as the assembly is a plug in unit.
The set is a bit tired but still gives a fair picture on the original Mullard AW36-21 electrostatically focused CRT. As can be seen from the picture, a very odd effect is taking place between the final anode 'cylinder' and the focus electrode.
Examination shows a mass of tiny glowing particles deposited on the neck of the tube and an intense light rather like a discharge lamp between the two electrodes mentioned earlier. Do not confuse this with the classic 'Argon' glow from a soft tube that will not display any form of picture. The glow worm effect of my tube has no effect on the picture and all the controls work quite normally. I can only think it has some bits of swarf that have become trapped in the gun assemblies electron stream causing them to glow. [Its quite spooky...Are you there Jon...]
I have witnessed many strange secondary emission faults in tubes over the years whilst working in close contact with a brilliant tube re builder but never this one! So there you go, you learn something every day.

high_vacuum_house · 17th Oct 2009, 5:53 pm

Hello there,

Looking at it, it seems quite white in colour and you say that "Examination shows a mass of tiny glowing particles deposited on the neck of the tube" then could it be particles of the phosphor coating that has flaked off the screen and settled on the CRT wall where it is exited and giving off light by stray electrons and other things going on aroung the electron gun area?
Could the CRT or the telly somehow ended up on its back (i.e faceplate looking upwards) then gravity pulling the loose phosphor particles down?

Christopher Capener

Lloyd 1985 · 17th Oct 2009, 7:12 pm

Hi,
I thought I saw something similar in my tv22 tube neck, but it wasn't that bright, so was probably just a reflection from the tube face. saying that though, I used to have a little hitachi black and white tv, and remember looking through the slots on the back and seeing what I thought at the time was the picture being 'projected' from the tube neck, which must have been the electron beam just touching the tube wall just after the scan coils, you could see what looked like those particles glowing on the sides of the tube. must be something left over when they make the tubes? I'm sure someone posted on here about crt manufacture, where they put the tube face down and pour in the phosphor 'soup' to lay the screen.

regards,
lloyd.

Heatercathodeshort · 17th Oct 2009, 10:27 pm

Hello Christopher,
My thoughts too with this but its the intense glow between the final anode and focus electrode that really has me wondering. It like a mini xenon headlamp!
The set may well have been stored badly as it was pulled off the tip around 10 years ago.
Hello Lloyd, As Chris said it could well be due to screen material or impurities in the tube itself. Maybe a particle has got trapped in the gun and is being excited by the beam. Wonderful things CRT's! Regards, John.

glowinganode · 17th Oct 2009, 11:07 pm

Oooer, how strange. Is the intensity of the glow in relation to the brightness of the raster?
Rob.

Heatercathodeshort · 18th Oct 2009, 8:03 pm

Not at all Rob. The picture is quite normal and the brightness control or the picture content has no effect on it. It is so bright that in a darkened room the slots in the cabinet back are projected onto the wall behind. It dies with the eht and builds with it.
Never seen anything quite like it. Most odd. J.

Tazman1966 · 18th Oct 2009, 8:31 pm

Really strange John. Have you stuck the CRT tester on it to see if it detects anything unusual?

glowinganode · 18th Oct 2009, 8:32 pm

Sorry if I'm being a bit slow, but with the brightness turned right down i.e. the beam cut off does the glow still occur? If so, surely this means the effect is caused by the electric field rather than the cathode ray? I can't see that an internal arc would give out this amount of light indefinately. Out of interest, what colour is the getter?
Even more confused, Rob.

Heatercathodeshort · 19th Oct 2009, 9:07 am

The brightness control has no effect on the brightness of the discharge. The getter is quite reasonable but the tube is not displaying the effects of a partial loss of vacuum that results in a purple type glow between the electrodes and collapse of eht. A total loss of course results in just simple arcing. This silent discharge is between the final and focus electrodes and thinking about it can only be some form of impurity trapped in the gap, being excited by the 14kv or so of EHT. Its an odd one. J.

17th Oct 2009, 11:37 am	#1
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	BUSH TV63 strange CRT phenomenon. Last night I spent a couple of hours pumping life back into this 14" Bush table model TV63. Another Forum member has a fault on the receiver unit of his console version and rather than struggle with the huge cabinet on the bench decided to use the TV63 as a 'test rig' as the assembly is a plug in unit. The set is a bit tired but still gives a fair picture on the original Mullard AW36-21 electrostatically focused CRT. As can be seen from the picture, a very odd effect is taking place between the final anode 'cylinder' and the focus electrode. Examination shows a mass of tiny glowing particles deposited on the neck of the tube and an intense light rather like a discharge lamp between the two electrodes mentioned earlier. Do not confuse this with the classic 'Argon' glow from a soft tube that will not display any form of picture. The glow worm effect of my tube has no effect on the picture and all the controls work quite normally. I can only think it has some bits of swarf that have become trapped in the gun assemblies electron stream causing them to glow. [Its quite spooky...Are you there Jon...] I have witnessed many strange secondary emission faults in tubes over the years whilst working in close contact with a brilliant tube re builder but never this one! So there you go, you learn something every day. Attached Thumbnails

17th Oct 2009, 5:53 pm	#2
high_vacuum_house Octode Join Date: May 2003 Location: Belper Derbyshire Posts: 1,936	Re: BUSH TV63 strange CRT phenomenon. Hello there, Looking at it, it seems quite white in colour and you say that "Examination shows a mass of tiny glowing particles deposited on the neck of the tube" then could it be particles of the phosphor coating that has flaked off the screen and settled on the CRT wall where it is exited and giving off light by stray electrons and other things going on aroung the electron gun area? Could the CRT or the telly somehow ended up on its back (i.e faceplate looking upwards) then gravity pulling the loose phosphor particles down? Christopher Capener __________________ Interests in the collection and restoration of Tefifon players and 405 line television

17th Oct 2009, 7:12 pm	#3
Lloyd 1985 Nonode Join Date: Jun 2008 Location: Coningsby, Lincolnshire, UK. Posts: 2,821	Re: BUSH TV63 strange CRT phenomenon. Hi, I thought I saw something similar in my tv22 tube neck, but it wasn't that bright, so was probably just a reflection from the tube face. saying that though, I used to have a little hitachi black and white tv, and remember looking through the slots on the back and seeing what I thought at the time was the picture being 'projected' from the tube neck, which must have been the electron beam just touching the tube wall just after the scan coils, you could see what looked like those particles glowing on the sides of the tube. must be something left over when they make the tubes? I'm sure someone posted on here about crt manufacture, where they put the tube face down and pour in the phosphor 'soup' to lay the screen. regards, lloyd.

17th Oct 2009, 10:27 pm	#4
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: BUSH TV63 strange CRT phenomenon. Hello Christopher, My thoughts too with this but its the intense glow between the final anode and focus electrode that really has me wondering. It like a mini xenon headlamp! The set may well have been stored badly as it was pulled off the tip around 10 years ago. Hello Lloyd, As Chris said it could well be due to screen material or impurities in the tube itself. Maybe a particle has got trapped in the gun and is being excited by the beam. Wonderful things CRT's! Regards, John.

17th Oct 2009, 11:07 pm	#5
glowinganode Octode Join Date: Apr 2009 Location: Aylesbury, Buckinghamshire, UK. Posts: 1,522	Re: BUSH TV63 strange CRT phenomenon. Oooer, how strange. Is the intensity of the glow in relation to the brightness of the raster? Rob. __________________ We have done so much, for so long, with so little, we are now qualified to do anything with nothing.

18th Oct 2009, 8:03 pm	#6
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: BUSH TV63 strange CRT phenomenon. Not at all Rob. The picture is quite normal and the brightness control or the picture content has no effect on it. It is so bright that in a darkened room the slots in the cabinet back are projected onto the wall behind. It dies with the eht and builds with it. Never seen anything quite like it. Most odd. J.

18th Oct 2009, 8:31 pm	#7
Tazman1966 Nonode Join Date: May 2006 Location: St Albans, Herts, UK. Posts: 2,194	Re: BUSH TV63 strange CRT phenomenon. Really strange John. Have you stuck the CRT tester on it to see if it detects anything unusual? __________________ All the very best, Tas

18th Oct 2009, 8:32 pm	#8
glowinganode Octode Join Date: Apr 2009 Location: Aylesbury, Buckinghamshire, UK. Posts: 1,522	Re: BUSH TV63 strange CRT phenomenon. Sorry if I'm being a bit slow, but with the brightness turned right down i.e. the beam cut off does the glow still occur? If so, surely this means the effect is caused by the electric field rather than the cathode ray? I can't see that an internal arc would give out this amount of light indefinately. Out of interest, what colour is the getter? Even more confused, Rob. __________________ We have done so much, for so long, with so little, we are now qualified to do anything with nothing. Last edited by glowinganode; 18th Oct 2009 at 8:42 pm. Reason: correction

19th Oct 2009, 9:07 am	#9
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: BUSH TV63 strange CRT phenomenon. The brightness control has no effect on the brightness of the discharge. The getter is quite reasonable but the tube is not displaying the effects of a partial loss of vacuum that results in a purple type glow between the electrodes and collapse of eht. A total loss of course results in just simple arcing. This silent discharge is between the final and focus electrodes and thinking about it can only be some form of impurity trapped in the gap, being excited by the 14kv or so of EHT. Its an odd one. J.