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Old 15th Feb 2019, 3:45 pm   #41
merlinmaxwell
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Default Re: Types of CRT used in colour TV's.

My granddad had a renta colour TV (mid 70's) and the colour went wonky, he took the back off and twiddled all the colourful knobs to try and fix it. Yes, it was the convergence panel and I was called in to adjust it near enough so the repair man didn't know. Ever tried to converge a delta tube without a crosshatch generator, you pray for subtitles and film captions!
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Old 15th Feb 2019, 4:33 pm   #42
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Default Re: Types of CRT used in colour TV's.

I did think that another company used the trinitron design, I think I heard it mentioned in a video, but wasn't sure how many did, and who did

I'd be interested to know the different types of tubes that didn't make it to the market, if anyone knows of anywhere that has information?

I'll search beam index's up and get reading, I'll have a look at the Indextron, too.

Thanks
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Old 15th Feb 2019, 4:40 pm   #43
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Default Re: Types of CRT used in colour TV's.

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Originally Posted by merlinmaxwell View Post
My granddad had a renta colour TV (mid 70's) and the colour went wonky, he took the back off and twiddled all the colourful knobs to try and fix it. Yes, it was the convergence panel and I was called in to adjust it near enough so the repair man didn't know. Ever tried to converge a delta tube without a crosshatch generator, you pray for subtitles and film captions!
How does the colour go wonky, do they just come out of alignment?

What would've happened if you hadn't improved it enough so the repair man didn't know that he'd fiddled with the convergence?

Why would you want captions after? Can it mess the sound up, too?

(Sorry for all the questions, i'm just curious)

Thanks
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Old 15th Feb 2019, 5:00 pm   #44
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Default Re: Types of CRT used in colour TV's.

It was strictly forbidden to remove the back of a rental set since it was the property of the rental company. I'm not sure what the penalty would have been but suspect it would have meant the customer would be liable to pay the full cost of the set, and probably be blacklisted from renting again. It would have been in the terms and conditions of the rental agreement.

I was always fascinated when the "telly man" had to call round, and often asked him a lot of questions about what was wrong and what he was doing. Not all the engineers were obliging with information though. It was seeing the engineers at work that sparked my interest and started me on that path myself, though I never worked for a rental company.

The "colour going wonky" could have been a lot of different fault conditions, either affecting a single colour or the whole decoder. People would see the coloured controls inside on the convergence panel and assume these adjusted the colours. I know that was my impression before I learned what they really did,
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Old 15th Feb 2019, 7:50 pm   #45
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Default Re: Types of CRT used in colour TV's.

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I did think that another company used the trinitron design, I think I heard it mentioned in a video, but wasn't sure how many did, and who did
Mitsubishi, as mentioned a few posts upthread, with their "Diamondtron" - which was rather good, I had a few hundred Diamondtron VGA monitors under my curatorship a couple of decades back, bought as a batch when some production-problem or other meant we couldn't get enough Trinitrons for the project.

The "Beam-indexing" tube - sometimes called a "Zebra tube" by Sylvania - did actually make it into production in some large early-1960s ATC- and RADAR-type displays - I remember one which only had two colours - one for the symbols of the aircraft and one for the text with call, flight-level etc.
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Old 15th Feb 2019, 8:40 pm   #46
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Default Re: Types of CRT used in colour TV's.

Hi.

A good technical description of the Mullard/Philips 20AX system is in the attached file. The 20AX in line gun system was Philips replacement to their delta gun CRTs. The later simplified 30AX system was a development of 20AX.

Regards,
Symon
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File Type: pdf Mullard Philips 20AX System.pdf (844.8 KB, 26 views)
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Old 15th Feb 2019, 9:25 pm   #47
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Default Re: Types of CRT used in colour TV's.

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Originally Posted by Clydeuk View Post
It was strictly forbidden to remove the back of a rental set since it was the property of the rental company. I'm not sure what the penalty would have been but suspect it would have meant the customer would be liable to pay the full cost of the set, and probably be blacklisted from renting again. It would have been in the terms and conditions of the rental agreement.

I was always fascinated when the "telly man" had to call round, and often asked him a lot of questions about what was wrong and what he was doing. Not all the engineers were obliging with information though. It was seeing the engineers at work that sparked my interest and started me on that path myself, though I never worked for a rental company.

The "colour going wonky" could have been a lot of different fault conditions, either affecting a single colour or the whole decoder. People would see the coloured controls inside on the convergence panel and assume these adjusted the colours. I know that was my impression before I learned what they really did,
Oh right, I never knew that. It makes a lot of sense though. What if it were opened by a qualified engineer from the same company?

I’d be just as interested too, it’s a shame that everything is just replaced when broken, i’d much rather it got fixed. Its this forum that sparked my interest, so i guess its fairly similar - me reading about the fixes of tech on here.

I think I would’ve thought the same, to be honest.
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Old 15th Feb 2019, 9:29 pm   #48
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Default Re: Types of CRT used in colour TV's.

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Why would you want captions after?
Anything white and made of lines helps in adjusting convergence. Subtitles did for the bottom of the picture and lasted a lot longer than credits, no VCR to rewind an play again. And only three channels to chose from.
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Old 15th Feb 2019, 9:36 pm   #49
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Default Re: Types of CRT used in colour TV's.

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Originally Posted by Philips210 View Post
A good technical description of the Mullard/Philips 20AX system is in the attached file. The 20AX in line gun system was Philips replacement to their delta gun CRTs. The later simplified 30AX system was a development of 20AX.
Thanks for that link! I just had a quick look and noticed the thin looking CRT. Were all of the IL tubes that thin, I have seen quite a few CRTs this thin but i have no idea makes and models of them.

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Old 15th Feb 2019, 9:56 pm   #50
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Default Re: Types of CRT used in colour TV's.

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Originally Posted by merlinmaxwell View Post
Anything white and made of lines helps in adjusting convergence. Subtitles did for the bottom of the picture and lasted a lot longer than credits, no VCR to rewind an play again. And only three channels to chose from.
I did think it would be for the white to adjust colour. Is the cross hatch just used to allign the colour all over the screen veryically and horizontally?

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Old 15th Feb 2019, 10:00 pm   #51
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Default Re: Types of CRT used in colour TV's.

Hi.

The Philips 20AX and 30AX used 110 degree deflection so were slim compared to any other CRTs that used 90 degree deflection.

The first generation delta gun CRTs were 90 degree and in the early 1970s, 110 degree deltas became available.
In the main, 90 degree deflection is for small screen sizes up to 20". For the larger sizes ie 22" and above, 110 degree deflection is the norm. An exception is a 20" version of both 20AX and 30AX CRTs.

Of course. 110 degree deflection in monochrome CRTs was around long before colour CRTs adopted this approach.

Regards
Symon.
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Old 15th Feb 2019, 10:08 pm   #52
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Default Re: Types of CRT used in colour TV's.

Quote:
Originally Posted by Clydeuk View Post
It was strictly forbidden to remove the back of a rental set since it was the property of the rental company. I'm not sure what the penalty would have been but suspect it would have meant the customer would be liable to pay the full cost of the set, and probably be blacklisted from renting again. It would have been in the terms and conditions of the rental agreement.
I had a little chuckle!

We had an elderly lady who would remove the speaker grille from her G8 and twiddle all the pots to their fully CCW extreme, replace the grille, then call us out for a poor picture. She did this maybe once a month, and would deny that anybody had tampered with it although it was obvious.

We didn't mind mind too much, the tea and biscuits were good and she probably was lonely.

TV Rental has a sort of charity work feel to it back in the '70s and 80s when I was involved, parts and labour were pre-paid in the customers rental, in fact we called the customers "subscribers".

After one company-wide shake up, we got a delegation of new management visit the depots, and lecture about only being in business to make a profit.

Shocking!

<Edit> Oh I just remembered, I even put a note behind the grille that said "DON'T TOUCH" but even that did't dissuade her entirely.
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Old 15th Feb 2019, 10:11 pm   #53
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Default Re: Types of CRT used in colour TV's.

This is a very interesting thread with lots of interesting information!
It seems there are some posts missing from the start though as the first post starts with a quote and there are no pictures of what is being discussed but there is a reference to how good "the tube " is?
Has it been split from another thread for some reason? If so can anyone direct me to the original thread please? As it is this thread seems to start a bit disjointed....


Rich.
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Old 15th Feb 2019, 10:20 pm   #54
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Default Re: Types of CRT used in colour TV's.

Quote:
Originally Posted by rambo1152 View Post
We had an elderly lady who would remove the speaker grille from her G8 and twiddle all the pots to their fully CCW extreme, replace the grille, then call us out for a poor picture. She did this maybe once a month, and would deny that anybody had tampered with it although it was obvious.
I had a similar problem with Varicap Thorn 3500s we had out on rental some customers couldn't resist opening the little door on the back of the set and fiddling with the multi turn tuning pots then call you out because BBC1 was on the ITV button and vice versa
The sets had good AFC and didn't drift off tune so why they played around I have no idea. it was always the same customers and it was always blamed on the Grandchildren...
Thorn had obviously anticipated this and provided a convenient hole in the door and escutcheon that a suitable screw could be inserted to lock the door. No more muddled channels!
Getting back to CRTs when I was training the firm had a lot of Hybrid Pye sets out on rent and while the 22" delta gun tubes were on the whole still giving good pictures the 26" A67 tubes fitted to the CT203 were starting to look poor. I later found out that a lot of tubes labelled as Mullard were in fact American imports, possibly Sylvania?
Guess who got the job of hauling these monsters out and fitting Cheapo "Sparkoblatt" reguns?

These tubes were terrible and apart from the sparking over when they were first fitted they usually needed a lot of setting up to get reasonably good convergence and purity.

One morning I had just finished fitting one and after setting the purity and static convergence I was surprised to find the dynamic convergence was excellent...

Just at that moment one of the senior engineers walked past "look at this " I commented to him "I only had to set the statics and it's spot on".

He walked over to the set and twiddled every pot on the convergence panel saying "You won't learn anything from that will you?"
From that I learnt alright... Keep my gob shut!

Last edited by slidertogrid; 15th Feb 2019 at 10:37 pm.
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Old 15th Feb 2019, 10:22 pm   #55
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Default Re: Types of CRT used in colour TV's.

Hi

Another good article, this time on the then newly developed PIL CRT can be found in the June 1973 issue of TELEVISION magazine available here https://www.americanradiohistory.com...UK-1973-06.pdf

Regards,
Symon
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Old 15th Feb 2019, 10:49 pm   #56
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Default Re: Types of CRT used in colour TV's.

Hi

Further good reading. Again in TELEVISION magazine, a series of articles by Eugene Trundle entitled "The Development of Colour Tubes" was in the June to October 1986 issues. These are also available from American Radio History website, eg the first part https://www.americanradiohistory.com...UK-1986-06.pdf

The October issue had an article on beam indexed tubes but for some reason appears to be missing in the ARH copy. I should have this issue to hand so can provide a scan of the article if anyone wants a copy.

Regards,
Symon
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Old 15th Feb 2019, 11:03 pm   #57
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Default Re: Types of CRT used in colour TV's.

Quote:
Originally Posted by Philips210 View Post
The Philips 20AX and 30AX used 110 degree deflection so were slim compared to any other CRTs that used 90 degree deflection.

The first generation delta gun CRTs were 90 degree and in the early 1970s, 110 degree deltas became available.
In the main, 90 degree deflection is for small screen sizes up to 20". For the larger sizes ie 22" and above, 110 degree deflection is the norm. An exception is a 20" version of both 20AX and 30AX CRTs.

Of course. 110 degree deflection in monochrome CRTs was around long before colour CRTs adopted this approach.
Doesnt a certain degree deflection give x-rays when set up in a certain way?

Do different degrees give a different picture quality, or give any improvements other than size difference?

Why didnt colour sets start with 110 degree deflection CRTs if they already existed?

Thanks
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Old 15th Feb 2019, 11:19 pm   #58
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Default Re: Types of CRT used in colour TV's.

Quote:
Originally Posted by rambo1152 View Post
We had an elderly lady who would remove the speaker grille from her G8 and twiddle all the pots to their fully CCW extreme, replace the grille, then call us out for a poor picture.
Hi

It was a mixed blessing having the convergence unit accessible from the front of the set.
The 520 series G8's front mounted convergence unit was though altogether much more reliable than the toasty rear mounted board as in the later G8s ie the 550 series. The hot running wirewound pots being mounted in an aluminium chassis in the 520 convergence unit helped to dissipate the heat hence better reliability.

Regards,
Symon.
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Old 15th Feb 2019, 11:23 pm   #59
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Default Re: Types of CRT used in colour TV's.

Quote:
Originally Posted by rambo1152 View Post

I had a little chuckle!

We had an elderly lady who would remove the speaker grille from her G8 and twiddle all the pots to their fully CCW extreme, replace the grille, then call us out for a poor picture. She did this maybe once a month, and would deny that anybody had tampered with it although it was obvious.

TV Rental has a sort of charity work feel to it back in the '70s and 80s when I was involved, parts and labour were pre-paid in the customers rental, in fact we called the customers "subscribers".

After one company-wide shake up, we got a delegation of new management visit the depots, and lecture about only being in business to make a profit.

Shocking!

<Edit> Oh I just remembered, I even put a note behind the grille that said "DON'T TOUCH" but even that did't dissuade her entirely.
I had to laugh at little at that, I can just imagine it - it probably happened all over the country to all sorts of people

Id loved to have been a TV repairman back in the 70s and 80s, doing something enjoyable almost everyday
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Old 15th Feb 2019, 11:26 pm   #60
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Default Re: Types of CRT used in colour TV's.

Quote:
Originally Posted by slidertogrid View Post
This is a very interesting thread with lots of interesting information!
It seems there are some posts missing from the start though as the first post starts with a quote and there are no pictures of what is being discussed but there is a reference to how good "the tube " is?
Has it been split from another thread for some reason? If so can anyone direct me to the original thread please? As it is this thread seems to start a bit disjointed.....
It is very interesting!

You’d be right about this thread being split.

Heres the original

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