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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. |
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11th Feb 2019, 11:15 am | #1 | |
Octode
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
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Types of CRT used in colour TV's.
Split from this thread:-
https://www.vintage-radio.net/forum/...d.php?t=152139 Quote:
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 |
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11th Feb 2019, 7:53 pm | #2 |
Octode
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,307
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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 |
12th Feb 2019, 12:02 am | #3 |
Octode
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
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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 |
12th Feb 2019, 12:30 am | #4 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,724
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Re: CRT is brighter to one side [Hitachi CTP213]
Cue for another trade test film.
https://www.youtube.com/watch?v=0Qd4IX3wpZk
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12th Feb 2019, 12:38 am | #5 |
Octode
Join Date: Jun 2018
Location: Essex, UK.
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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 |
12th Feb 2019, 12:40 am | #6 |
Octode
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,307
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Re: CRT is brighter to one side [Hitachi CTP213]
Thanks for that link, Graham!
I'll give that a watch now! |
12th Feb 2019, 1:23 am | #7 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,554
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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.
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12th Feb 2019, 1:36 am | #8 | |
Nonode
Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
Posts: 2,820
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Re: CRT is brighter to one side [Hitachi CTP213]
Quote:
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! |
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12th Feb 2019, 1:50 am | #9 | ||||||
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
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Re: CRT is brighter to one side [Hitachi CTP213]
Quote:
Quote:
Quote:
Quote:
https://www.youtube.com/results?sear...ube+rebuilding Quote:
Quote:
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-- Graham. G3ZVT Last edited by Graham G3ZVT; 12th Feb 2019 at 2:06 am. |
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12th Feb 2019, 1:51 am | #10 | |
Octode
Join Date: Jun 2018
Location: Essex, UK.
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Re: CRT is brighter to one side [Hitachi CTP213]
Quote:
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 |
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12th Feb 2019, 1:58 am | #11 | |
Octode
Join Date: Jun 2018
Location: Essex, UK.
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Re: CRT is brighter to one side [Hitachi CTP213]
Quote:
Where abouts are the two halves of the tubes fitted? Thanks |
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12th Feb 2019, 2:07 am | #12 | |
Octode
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,307
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Re: CRT is brighter to one side [Hitachi CTP213]
Quote:
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 |
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12th Feb 2019, 2:10 am | #13 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
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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. |
12th Feb 2019, 2:14 am | #14 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,724
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Re: CRT is brighter to one side [Hitachi CTP213]
It's shown in the film in post #227
The principles are much the same for PIL tube manufacture.
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12th Feb 2019, 2:20 am | #15 | |
Octode
Join Date: Jun 2018
Location: Essex, UK.
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Re: CRT is brighter to one side [Hitachi CTP213]
Quote:
Thanks |
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12th Feb 2019, 2:21 am | #16 |
Octode
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,307
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Re: CRT is brighter to one side [Hitachi CTP213]
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12th Feb 2019, 2:25 am | #17 |
Octode
Join Date: Jun 2018
Location: Essex, UK.
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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?) |
12th Feb 2019, 2:28 am | #18 | |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
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Re: CRT is brighter to one side [Hitachi CTP213]
Quote:
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. |
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12th Feb 2019, 2:45 am | #19 |
Octode
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,307
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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 |
12th Feb 2019, 7:33 am | #20 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
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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
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-- Graham. G3ZVT Last edited by Graham G3ZVT; 12th Feb 2019 at 7:41 am. |