UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Components and Circuits

Notices

Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

Reply
 
Thread Tools
Old 11th Feb 2019, 11:15 am   #1
1100 man
Heptode
 
1100 man's Avatar
 
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 894
Default Types of CRT used in colour TV's.

Split from this thread:-

https://www.vintage-radio.net/forum/...d.php?t=152139




Quote:
Originally Posted by InsertNameHere View Post
Wouldn’t it be okay though if i were to mark the pots and then adjust the yoke as the set is self convergence as it’s a PIL set.
HI Aaron,

PIL tubes rely (apart from the design of the tube) on the accurate positioning of the scan coils to achieve good convergence. During manufacture the scan coils (yoke assembly) are positioned using rubber wedges glued in place. Replacement tubes came with scan coils already mounted to the tube neck.

I did notice a very slight tilt to the picture in one of your early pictures, but it was very slight and within the tolerance I would expect.
I would advise leaving it alone (although it would annoy me too!). You will probably find the scan coil assembly well and truly stuck to the tube neck so you wont be able to rotate it anyway.

I'm very impressed with the picture quality- the tube looks in excellent condition!

All the best
Nick
1100 man is offline   Reply With Quote
Old 11th Feb 2019, 7:53 pm   #2
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 525
Default Re: CRT is brighter to one side [Hitachi CTP213]

Hi

Oh I never realised that, I think delta gun CRTs are more common (?) so the majority of videos I have seen were most likely for delta gun sets and some were even American and they have a slightly different system, I think - not too sure.

The tilt is bearable, but it'd be better if it could be straightened out, but I think i'll leave it. After all, it just adds to the character of the set!

I'm impressed too, I knew CRTs don't always have the greatest picture, and some being older, like mine, i'd have thought they "wear out" a bit, but I was really impressed when I turned the set on!

The whole set is in excellent condition, there are no scratches, dents, chips or anything, the only noticeable evidence of use is the power button fading slightly, and that's it!

Thanks
InsertNameHere is offline   Reply With Quote
Old 12th Feb 2019, 12:02 am   #3
1100 man
Heptode
 
1100 man's Avatar
 
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 894
Default Re: CRT is brighter to one side [Hitachi CTP213]

Hi Aaron,
The first generation of colour TV's from the late 1960's, used delta gun CRT's. These required a whole array of convergence adjustments to get the three colours to align reasonably well over the whole screen. They also needed a very large yoke assembly around the tube neck to achieve this. Converging one of these sets takes a while and is an art in itself. They don't like being moved about too much either as this can upset all the adjustments. The three guns in the tube neck are arranged in a triangle and the phosphor 'dots' on the screen are also in triangles.

Then in about 1973/74, the PIL tube arrived. I don't know who developed it but I first came across it in the Thorn 9000 sets. It stands for 'precision in line' and the three guns are mounted next to each other in a line. Due to improved design and manufacturing tolerances, these needed much less correction to get the three beams to align. Part of that correction, though, was to accurately set the exact angle of the scan coil assembly during manufacture. That's why trying to rotate them could cause convergence errors. The setting of the coils usually involved the use of rubber wedges jammed under the coils and glued in place.

If you look closely at your screen, you will see the three coloured phosphors are arranged in vertical stripes.
The PIL tube was further developed & refined, but really remained until the end of CRT production.

CRT's certainly do wear out. The emission (the amount of electrons that a gun can produce) decays with use generally giving a low contrast, smeary picture often with a noticeable colour tint. Your tube looks in excellent condition.

CRT's are capable of giving excellent pictures although the resolution is not that great. They have served us well and were an amazing technology. To be able to mass produce them was an incredible achievement.

All the best
Nick
1100 man is offline   Reply With Quote
Old 12th Feb 2019, 12:30 am   #4
rambo1152
Octode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 1,048
Default Re: CRT is brighter to one side [Hitachi CTP213]

Cue for another trade test film.
https://www.youtube.com/watch?v=0Qd4IX3wpZk
__________________
--
Graham.
G3ZVT
rambo1152 is offline   Reply With Quote
Old 12th Feb 2019, 12:38 am   #5
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 525
Default Re: CRT is brighter to one side [Hitachi CTP213]

Hi

I didn't realise DG sets had larger yokes, although I can see why, as aren't the guns angled? (I'm not too sure on that) On my hunt for a 70s set I referred to here often (As i think you know) to see which would be a good set for me to begin with. I was often told to keep away from certain sets for a beginner set due to convergence, so i guess these were DG sets and were early 70s sets.

Would a shadow mask from a DG set not work on a PIL set and vice versa with the correct adjustments, or would it just be a mess?

With the yokes being convergence, does that mean that some sets would've been wonky for the sake of a good picture?

About the decaying guns, so when a CRT dies, in order to get it up and running again, it'd need to be re-gunned in some way. I was actually doing some research online and i came across a website with someone who had the exact same issue as i had with the smeared, off coloured picture (On a monitor I believe) and my I was gutted to read that it could be the tube dying - so of course, when i got mine running again i couldn't have been happier with the result.

I think with CRTs, the colour given often makes up for the resolution, and when you're sitting a sensible distance away, the resolution isn't too much of an issue (Not for me anyway) of course, sitting up close to the set I notice the imperfections in the resolution but im rarely up close to it.

I find it fascinating how complicated CRT TVs are, compared to TVs now, and the fact that the inventors had very little to base them off, and to have been created in the 1920s and 30s, I find that even more fascinating.

Thanks
InsertNameHere is offline   Reply With Quote
Old 12th Feb 2019, 12:40 am   #6
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 525
Default Re: CRT is brighter to one side [Hitachi CTP213]

Thanks for that link, Graham!

I'll give that a watch now!
InsertNameHere is offline   Reply With Quote
Old 12th Feb 2019, 1:23 am   #7
Refugee
Dekatron
 
Refugee's Avatar
 
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 3,782
Default Re: CRT is brighter to one side [Hitachi CTP213]

The shadow mask you talk of is an internal component of the tube and can only be accessed by braking the tube apart. It is a component behind the viewing screen and is fitted before the two halves of the tube are joined together and well before the neck and guns are fitted.
Refugee is offline   Reply With Quote
Old 12th Feb 2019, 1:36 am   #8
Lloyd 1985
Octode
 
Lloyd 1985's Avatar
 
Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
Posts: 1,461
Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by InsertNameHere View Post
Would a shadow mask from a DG set not work on a PIL set and vice versa with the correct adjustments, or would it just be a mess?
No is the simple answer to that, the shadow mask is an integral part of the CRT itself, it sits just behind the phosphor coating, and the electron beam passes through it, it’s there to direct the 3 beams to their intended phosphor colour. Have a look on YouTube, I’m sure there was a video of someone dissecting a Sony trinitron CRT, or even some of the nasty videos of people bashing TVs with hammers, you will see the shadow mask as what looks like a sheet of metal behind the faceplate glass.

The video that Rambo1152 has linked to will show you a delta gun CRT being assembled, you get to see how the shadow mask is used during manufacture for positioning the phosphor dots (I can’t think of a better way to describe it!) and that a particular shadow mask has to stay with the faceplate it was used with.

If you want, I can get a close up photo of the slots in a PIL shadow mask, as I pulled one from a smashed CRT once.

Regards
Lloyd

Ps, the photo is of my HMV 2711 that has the Thorn 3500 chassis in it, and a 26” delta gun CRT, it’s a right pain in the backside to get the convergence good on it!! There is an old thread from when I got the set in 2009 on here somewhere, with shots of inside the set too, see how different it is inside to your Hitachi!
Attached Thumbnails
Click image for larger version

Name:	272B56B2-612A-42CC-9581-B72B4BF5F9AC.jpg
Views:	70
Size:	66.8 KB
ID:	178244  
Lloyd 1985 is offline   Reply With Quote
Old 12th Feb 2019, 1:50 am   #9
rambo1152
Octode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 1,048
Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by insertnamehere View Post
i didn't realise dg sets had larger yokes, although i can see why, as aren't the guns angled? (i'm not too sure on that)
yes they are.

Quote:
would a shadow mask from a dg set not work on a pil set and vice versa with the correct adjustments, or would it just be a mess?
No. The shadow mask in a PIL tube is called an aperture grill has slots instead of holes, each slot is wide enough to guide the three beams to their respective phosphor dots.

Quote:
With the yokes being convergence, does that mean that some sets would've been wonky for the sake of a good picture?
That's very perceptive of you Aaron, you have thought that through. Take the blue gun for example, being at the top of the triangle it projects a trapezoidal raster on the screen, the red and blue do the same at 45 degrees. Correcting these errors is called dynamic convergence, and correcting the overall picture is called geometry correction.

Quote:
About the decaying guns, so when a crt dies, in order to get it up and running again, it'd need to be re-gunned in some way. I was actually doing some research online and i came across a website with someone who had the exact same issue as i had with the smeared, off coloured picture (on a monitor i believe) and my i was gutted to read that it could be the tube dying - so of course, when i got mine running again i couldn't have been happier with the result.
Re-gunning (rebuilding) CRTs used to be a cost effective industry not any more. Some more videos to watch
https://www.youtube.com/results?sear...ube+rebuilding

Quote:
I think with crts, the colour given often makes up for the resolution, and when you're sitting a sensible distance away, the resolution isn't too much of an issue (not for me anyway) of course, sitting up close to the set i notice the imperfections in the resolution but im rarely up close to it.
It's actually the monochrome element (luminance) that has the high resolution, the colour element (chrominance) is just a smear by comparison. The whole thing is an optical illusion.

Quote:
I find it fascinating how complicated crt tvs are, compared to tvs now, and the fact that the inventors had very little to base them off, and to have been created in the 1920s and 30s, i find that even more fascinating.
Actually appearances are deceptive. The electronics in a modern set is infinitely more complex than a vintage one, but it's all done in those microchips, and we as repair people don't need to concern ourselves with how they work internally, nor, in many cases, do the chip manufacturers want us to know how they work.
__________________
--
Graham.
G3ZVT

Last edited by rambo1152; 12th Feb 2019 at 2:06 am.
rambo1152 is offline   Reply With Quote
Old 12th Feb 2019, 1:51 am   #10
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 525
Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by Lloyd 1985 View Post
No is the simple answer to that, the shadow mask is an integral part of the CRT itself, it sits just behind the phosphor coating, and the electron beam passes through it, it’s there to direct the 3 beams to their intended phosphor colour. Have a look on YouTube, I’m sure there was a video of someone dissecting a Sony trinitron CRT, or even some of the nasty videos of people bashing TVs with hammers, you will see the shadow mask as what looks like a sheet of metal behind the faceplate glass.

The video that Rambo1152 has linked to will show you a delta gun CRT being assembled, you get to see how the shadow mask is used during manufacture for positioning the phosphor dots (I can’t think of a better way to describe it!) and that a particular shadow mask has to stay with the faceplate it was used with.

If you want, I can get a close up photo of the slots in a PIL shadow mask, as I pulled one from a smashed CRT once.
I didn’t think it would, but i was just curious, i suppose thinking about it, it makes sense with delta guns having circles forming triangles (if that makes sense) and PIL having lines. I’d be fascinated to see if there was any simulation or anything of what a PIL set with a DG shadow masks’ picture would look, and vice versa.

I saw the part in the film you are talking about, which i then realised would of course make them incompatible with any other set, as you said about the manufacturing part too.

I’d love to see a close up of a PIL slot shadow mask, if you don’t mind?
I’ve never seen one demonstrated, they’ve always been Delta Gun sets.

I’ll look for that thread now, and give it a read and compare the two!

Thanks
InsertNameHere is offline   Reply With Quote
Old 12th Feb 2019, 1:58 am   #11
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 525
Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by Refugee View Post
The shadow mask you talk of is an internal component of the tube and can only be accessed by braking the tube apart. It is a component behind the viewing screen and is fitted before the two halves of the tube are joined together and well before the neck and guns are fitted.
I didnít realise thats how the tubes were made, i never really put much thought into how they were made really, itís never crossed my mind. I get the basic structure of a CRT and what has been made into it, but not how

Where abouts are the two halves of the tubes fitted?

Thanks
InsertNameHere is offline   Reply With Quote
Old 12th Feb 2019, 2:07 am   #12
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 525
Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by rambo1152 View Post
Re-gunning (rebuilding) CRTs used to be a cost effective industry not any more. Some more videos to watch
https://www.youtube.com/results?sear...ube+rebuilding
I never realised shadow masks’ would be different, but i understand why now. Are the shadow masks in DG sets and PIL sets named differently apart from Apeture grill and shadow mask? Perhaps this is why i’ve never seen an apeture grill due to never having searched it or even knowing what it was.

I thought i had read something about CRTs getting re-gunned. Could this still be done today with (say) NOS, by someone, who is very experienced in this field, at home, or is specialist equipment needed?

I’ll watch that video right after this reply!

Thanks
InsertNameHere is offline   Reply With Quote
Old 12th Feb 2019, 2:10 am   #13
Refugee
Dekatron
 
Refugee's Avatar
 
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 3,782
Default Re: CRT is brighter to one side [Hitachi CTP213]

The screen is one part and the cone and neck at the back is the other part.
Many later tubes had the two parts joined together by some kind of adhesive especially on VGA computer monitors.
I used to repair computer screens and the BER ones often broke up as they were thrown into the skip so that is how I know what tubes look like inside.
They were like vertical blinds in trinatron tubes.
Refugee is offline   Reply With Quote
Old 12th Feb 2019, 2:14 am   #14
rambo1152
Octode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 1,048
Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by InsertNameHere View Post
Where abouts are the two halves of the tubes fitted?
It's shown in the film in post #227
The principles are much the same for PIL tube manufacture.
__________________
--
Graham.
G3ZVT
rambo1152 is offline   Reply With Quote
Old 12th Feb 2019, 2:20 am   #15
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 525
Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by Refugee View Post
The screen is one part and the cone and neck at the back is the other part.
Many later tubes had the two parts joined together by some kind of adhesive especially on VGA computer monitors.
I used to repair computer screens and the BER ones often broke up as they were thrown into the skip so that is how I know what tubes look like inside.
They were like vertical blinds in trinatron tubes.
I saw a video a few days ago of someone replacing the tube in an American RCA set, or a Zenith, and he removed the front glass protective panel to clean it and had to cut through adhesive. Is this the same thing or slightly different.

Thanks
InsertNameHere is offline   Reply With Quote
Old 12th Feb 2019, 2:21 am   #16
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 525
Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by rambo1152 View Post
It's shown in the film in post #227
The principles are much the same for PIL tube manufacture.
I went back a watched that part, don’t know how i missed it but it makes sense now.

Thanks
InsertNameHere is offline   Reply With Quote
Old 12th Feb 2019, 2:25 am   #17
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 525
Default Re: CRT is brighter to one side [Hitachi CTP213]

Lloyd - I found your thread on the HMV and thats a much more confusing looking set! I’m glad i started off with a japanese set now!

I suppose when/if you’ve been in the trade you get to know them very well and the confusion of them fades away.

Wasn’t a common fault on Thorns droppers?

(I also thought of the TV set they used on Electric Dreams - I watched it on youtube fairly recently - is it the same set, or a similar model?)
InsertNameHere is offline   Reply With Quote
Old 12th Feb 2019, 2:28 am   #18
Refugee
Dekatron
 
Refugee's Avatar
 
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 3,782
Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by InsertNameHere View Post
I saw a video a few days ago of someone replacing the tube in an American RCA set, or a Zenith, and he removed the front glass protective panel to clean it and had to cut through adhesive. Is this the same thing or slightly different.
Those old RCA tubes had an old style implosion guard on them and are very different to the types used in UK sets and computer screens.
The adhesive between the implosion guard and the screen used to fail.
They were obsolete by the time we got colour TV.
The mask was more like the later ones but the tube itself was often a round screen type like early B/W sets.
Refugee is offline   Reply With Quote
Old 12th Feb 2019, 2:45 am   #19
InsertNameHere
Heptode
 
InsertNameHere's Avatar
 
Join Date: Jun 2018
Location: London, UK.
Posts: 525
Default Re: CRT is brighter to one side [Hitachi CTP213]

I did wonder if the US and UK designs, i think it may have been a colour set, but im not too sure.

The set was a “roundie” as he called it, like the early sets, as you say.

Thanks
InsertNameHere is offline   Reply With Quote
Old 12th Feb 2019, 7:33 am   #20
rambo1152
Octode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 1,048
Default Re: CRT is brighter to one side [Hitachi CTP213]

You've been watching Shango!
I wasn't aware of that cataract problem until I saw it on that channel, he has less reverence for vintage sets than most of us here
__________________
--
Graham.
G3ZVT

Last edited by rambo1152; 12th Feb 2019 at 7:41 am.
rambo1152 is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 4:44 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2018, Paul Stenning.