Digital Spy

Search Digital Spy
 

DS Forums

 
 

Colourising a black & white CRT TV.


Reply
Thread Tools Search this Thread
Old 27-07-2013, 23:31
Richardcoulter
Forum Member
 
Join Date: Jun 2002
Posts: 5,493

In the 1970's I once asked a TV repairman if it would be possible to convert a monochrome TV into a colour set.

After pondering for a bit, he said that the monetary cost and time of replacing various parts would not make it worthwhile and that one would be better off simply buying a colour set.

I realise that this is now purely an academic question, but do those on here who know much more about the subject than myself think he was right?

Did this position change over the years prior to the introduction of non CRT sets?

Thanks.
Richardcoulter is offline   Reply With Quote
Please sign in or register to remove this advertisement.
Old 28-07-2013, 03:20
Chris Frost
Forum Member
 
Join Date: Jun 2003
Location: Cheshire
Posts: 4,618
To do that you'd need to change the CRT tube from a monochrome to one with three colour phosphors, and change the drive electronics so that the set could receive and process a colour signal. That would constitute a major rebuild and the replacement of components (the CRT tube mainly) that make up the bulk of the cost of the set. So he was right from a practical point of view.
Chris Frost is offline   Reply With Quote
Old 28-07-2013, 10:08
Nigel Goodwin
Forum Member
 
Join Date: Apr 2006
Location: North Derbyshire
Posts: 38,098
In the 1970's I once asked a TV repairman if it would be possible to convert a monochrome TV into a colour set.

After pondering for a bit, he said that the monetary cost and time of replacing various parts would not make it worthwhile and that one would be better off simply buying a colour set.

I realise that this is now purely an academic question, but do those on here who know much more about the subject than myself think he was right?

Did this position change over the years prior to the introduction of non CRT sets?
No, nothing has changed (or could possibly change), the only puzzling part of this story is that the engineer 'pondered for a bit'.

It's not a case of 'replacing various parts', it's a case of removing all the insides of the TV, and replacing them with the insides from a colour TV.

The only sections that would be reusable would be the tuner, IF, and audio output stages (essentially the 'radio' parts of a TV, which have little to do with the picture).
Nigel Goodwin is offline   Reply With Quote
Old 28-07-2013, 16:50
Richardcoulter
Forum Member
 
Join Date: Jun 2002
Posts: 5,493
Thanks for sharing your expertise with me guys, I now know the answer to my question of long ago
Richardcoulter is offline   Reply With Quote
Old 28-07-2013, 19:00
Kodaz
Forum Member
 
Join Date: Jul 2008
Posts: 933
The only sections that would be reusable would be the tuner, IF, and audio output stages (essentially the 'radio' parts of a TV, which have little to do with the picture).
And even then you'd still have to modify the circuitry to extract and output the colour information as well.

However... believe it or not, there *was* once a way to convert a black-and-white TV to colour. A system called the Col-R-Tel was sold in the US in the 1950s.

It basically *converted* the NTSC colour signal into a field-sequential colour one, output it to the black-and-white set and colourised the picture by filtering it through a rotating (mechanical) colour wheel that filtered successive frames with red, green and then blue. IIRC it only worked with some sets, as it tied into their electronic circuitry.

While the US *had* rejected an earlier semi-mechanical sequential colour system in favour of NTSC (as the broadcast standard), this adapter wasn't compatible that earlier system. It was essentially an adaptor for NTSC.

How would it compare to a true colour CRT set? The wheel would have had to be much bigger than the TV screen itself (although TVs in the 1950s would have been very small by modern standards), there would have been some colour artifacts on moving images, the picture would be slightly degraded- and inferior to that of a colour CRT, and the wheel probably made some noise as well.

I'm not aware of such a thing having been sold in the UK (or any PAL country), probably because colour transmissions didn't start here until much later and things would have moved on by then.

(Disclaimer: I'm no expert on the subject- I read all this online... isn't the Internet wonderful? )
Kodaz is offline   Reply With Quote
Old 28-07-2013, 19:29
Nigel Goodwin
Forum Member
 
Join Date: Apr 2006
Location: North Derbyshire
Posts: 38,098
And even then you'd still have to modify the circuitry to extract and output the colour information as well.
No, there's nothing to 'modify' - at least not on older B&W sets, the later ones 'might' have a 4.43361875MHz notch filter to prevent the possibility of patterning on the screen, but that would be so simple to remove it wouldn't really count as 'modifying'

The colour decoder itself separates the luma and chroma, it's not part of the IF/detector - and is dead simple filtering anyway.
Nigel Goodwin is offline   Reply With Quote
Old 28-07-2013, 19:55
Kodaz
Forum Member
 
Join Date: Jul 2008
Posts: 933
No, there's nothing to 'modify' - at least not on older B&W sets, the later ones 'might' have a 4.43361875MHz notch filter to prevent the possibility of patterning on the screen, but that would be so simple to remove it wouldn't really count as 'modifying'

The colour decoder itself separates the luma and chroma, it's not part of the IF/detector - and is dead simple filtering anyway.
Well, I'll take your word for that as I'm not an expert, but when I said "modified" I had in mind that- at best- one would still require additional colour decoding circuitry (that I would have assumed the B/W sets ignore or- as you state- discard) and patch that in- which I assume is what you're suggesting.

If this is more likely than my imagined worst-case scenario, (which would have been that it would require extensive modification of the existing circuitry), fair enough, but you'd still need the colour decoding hardware, right?
Kodaz is offline   Reply With Quote
Old 28-07-2013, 20:18
Nigel Goodwin
Forum Member
 
Join Date: Apr 2006
Location: North Derbyshire
Posts: 38,098
Well, I'll take your word for that as I'm not an expert, but when I said "modified" I had in mind that- at best- one would still require additional colour decoding circuitry (that I would have assumed the B/W sets ignore or- as you state- discard) and patch that in- which I assume is what you're suggesting.

If this is more likely than my imagined worst-case scenario, (which would have been that it would require extensive modification of the existing circuitry), fair enough, but you'd still need the colour decoding hardware, right?
Yes, obviously - you would need a new PSU, colour decoder, RGB video amplifier stages, new line and frame output stages, and new EHT circuitry (usually line output derived).

Pretty well everything in the TV, apart from the 'radio' part as I mentioned previously.

It was seriously not a viable idea, not by any stretch of the imagination.

Think of it as similar to you having a moped, and wanting to convert it to a Ferrari
Nigel Goodwin is offline   Reply With Quote
Old 28-07-2013, 22:13
Gordie1
Forum Member
 
Join Date: Nov 2007
Location: North East
Posts: 5,059
In the 1970's I once asked a TV repairman if it would be possible to convert a monochrome TV into a colour set.

After pondering for a bit, he said that the monetary cost and time of replacing various parts would not make it worthwhile and that one would be better off simply buying a colour set.

I realise that this is now purely an academic question, but do those on here who know much more about the subject than myself think he was right?

Did this position change over the years prior to the introduction of non CRT sets?

Thanks.
Back in the day, there used to be salesmen travelling door to door offering a filter that went over your B&W TV that allegedly transformed it into colour.

I never seen one of these screens my self, but i heard people mentioning them when they knocked.

i might have to google it.
Gordie1 is online now   Reply With Quote
Old 28-07-2013, 23:18
Kodaz
Forum Member
 
Join Date: Jul 2008
Posts: 933
Back in the day, there used to be salesmen travelling door to door offering a filter that went over your B&W TV that allegedly transformed it into colour.

I never seen one of these screens my self, but i heard people mentioning them when they knocked.

i might have to google it.
Although the system I described used coloured filters, it wasn't quite *that* simplistic or cheap! The filters were part of a tri-colour wheel whose rotation was synced to the frame rate, and additional colour decoding and conversion electronics for the TV would also have been required.

The "filter" you describe sounds more like it was a silly (and ludicrously ineffective) colour overlay sheet (i.e. clear plastic film with one or more tinted areas). If so, it could only have been sold by blatantly misleading people (i.e. a borderline con!), since no-one in their right mind would have bothered otherwise!
Kodaz is offline   Reply With Quote
Old 29-07-2013, 00:28
Gordie1
Forum Member
 
Join Date: Nov 2007
Location: North East
Posts: 5,059
Although the system I described used coloured filters, it wasn't quite *that* simplistic or cheap! The filters were part of a tri-colour wheel whose rotation was synced to the frame rate, and additional colour decoding and conversion electronics for the TV would also have been required.

The "filter" you describe sounds more like it was a silly (and ludicrously ineffective) colour overlay sheet (i.e. clear plastic film with one or more tinted areas). If so, it could only have been sold by blatantly misleading people (i.e. a borderline con!), since no-one in their right mind would have bothered otherwise!
Hence why i never seen one myself i suppose.
Gordie1 is online now   Reply With Quote
Old 29-07-2013, 09:35
Nigel Goodwin
Forum Member
 
Join Date: Apr 2006
Location: North Derbyshire
Posts: 38,098
Back in the day, there used to be salesmen travelling door to door offering a filter that went over your B&W TV that allegedly transformed it into colour.

I never seen one of these screens my self, but i heard people mentioning them when they knocked.
I saw one once

I went to a customers house, where I knew they only had 405 TV - as I walked in I was initially shocked to see a 'colour' picture.

Once over that initial 'shock' it was obviously just a piece of coloured film over the screen - brown at the bottom, green in the middle, and blue at the top.
Nigel Goodwin is offline   Reply With Quote
Old 29-07-2013, 19:00
AidanLunn
Forum Member
 
Join Date: Apr 2010
Posts: 4,405
In the 1970's I once asked a TV repairman if it would be possible to convert a monochrome TV into a colour set.

After pondering for a bit, he said that the monetary cost and time of replacing various parts would not make it worthwhile and that one would be better off simply buying a colour set.

I realise that this is now purely an academic question, but do those on here who know much more about the subject than myself think he was right?

Did this position change over the years prior to the introduction of non CRT sets?

Thanks.
As this is the 1970s, depends what you meant by a black and white TV?

Converting B&W 625 to colour would have been far easier compared to a 405-line set, though still so difficult as to be impractical!
AidanLunn is offline   Reply With Quote
Old 29-07-2013, 19:18
PrinceGaz
Forum Member
 
Join Date: Mar 2006
Location: Newcastle
Posts: 8,012
As this is the 1970s, depends what you meant by a black and white TV?

Converting B&W 625 to colour would have been far easier compared to a 405-line set, though still so difficult as to be impractical!
Yes, as has been said, only the actual radio part would still be useable, and that is the cheapest part of the circuitry.

The CRT, the high-voltage driver circuitry, and filtering circuit feeding it, as well as the power-supply, would all need replacing. By the time you're finished, there's not much of the original television left.

There is one quite specific exception to the above about colourising a B&W TV, which is if you were using it to display certain specific early arcade games (around late 1970s era), most notably "Space Invaders": the monochrome display was made colour by applying physical colour-filters over the upper and lower parts of the screen (at a push you could probably use a felt-tip pen to achieve a similar result). Other games used different colours over different areas, but Space Invaders was by far the best known. Not what the OP intended, but probably the most widespread example of a "colour" B&W display.
PrinceGaz is offline   Reply With Quote
Old 29-07-2013, 20:00
Gordie1
Forum Member
 
Join Date: Nov 2007
Location: North East
Posts: 5,059
I saw one once

I went to a customers house, where I knew they only had 405 TV - as I walked in I was initially shocked to see a 'colour' picture.

Once over that initial 'shock' it was obviously just a piece of coloured film over the screen - brown at the bottom, green in the middle, and blue at the top.
Christ, so people actually did buy them then, LOL
Gordie1 is online now   Reply With Quote
Old 29-07-2013, 20:01
Nigel Goodwin
Forum Member
 
Join Date: Apr 2006
Location: North Derbyshire
Posts: 38,098
Converting B&W 625 to colour would have been far easier compared to a 405-line set, though still so difficult as to be impractical!
I was assuming 625 line all along

Not that much different to 405 lines really, except 405 lines would require the tuner and IF replacing as well, leaving only the sound output stage usable

But pretty minor 'extras' to a 625 line set.
Nigel Goodwin is offline   Reply With Quote
Old 29-07-2013, 20:02
Nigel Goodwin
Forum Member
 
Join Date: Apr 2006
Location: North Derbyshire
Posts: 38,098
Christ, so people actually did buy them then, LOL
I've only ever seen the one

Interesting the post above about Space Invaders, they did the same thing - I'd forgotten about that.
Nigel Goodwin is offline   Reply With Quote
Old 29-07-2013, 21:42
Gordie1
Forum Member
 
Join Date: Nov 2007
Location: North East
Posts: 5,059
I've only ever seen the one

Interesting the post above about Space Invaders, they did the same thing - I'd forgotten about that.
It does kinda work with old video games though, as they know beforehand where certain blocks will be, but over-layed on coronation street?, LOL
Gordie1 is online now   Reply With Quote
Old 29-07-2013, 21:53
AidanLunn
Forum Member
 
Join Date: Apr 2010
Posts: 4,405
I was assuming 625 line all along

Not that much different to 405 lines really, except 405 lines would require the tuner and IF replacing as well, leaving only the sound output stage usable

But pretty minor 'extras' to a 625 line set.
Plus probably even more mods to the line and frame output stages?

Ah, but this was the 70s - B&W TV could have meant two very different standards!
AidanLunn is offline   Reply With Quote
Old 30-07-2013, 09:17
Nigel Goodwin
Forum Member
 
Join Date: Apr 2006
Location: North Derbyshire
Posts: 38,098
Plus probably even more mods to the line and frame output stages?
Not really, it would need completely changing for colour anyway, so makes no difference - however, with a 625 line set you 'could' use the line and frame oscillators, but it would hardly be worth it.

But the whole question is pretty pointless, as I said initially you're basically ripping all the insides out, and fitting the insides from a colour TV in the same box.

To be fair, this is relatively common these days, fitting modern colour TV's inside antique TV cabinets - I recently did one for a museum display, fitting an LCD in an old Ecko cabinet

http://www.gulliversfun.co.uk/warrin...age-centre.htm
Nigel Goodwin is offline   Reply With Quote
Old 30-07-2013, 10:28
AidanLunn
Forum Member
 
Join Date: Apr 2010
Posts: 4,405
To be fair, this is relatively common these days, fitting modern colour TV's inside antique TV cabinets - I recently did one for a museum display, fitting an LCD in an old Ecko cabinet

http://www.gulliversfun.co.uk/warrin...age-centre.htm
I hope you didn't chuck away any of the chassis!

(Although restoring the thing to working condition would have gained my approval!)
AidanLunn is offline   Reply With Quote
Old 30-07-2013, 10:43
Nigel Goodwin
Forum Member
 
Join Date: Apr 2006
Location: North Derbyshire
Posts: 38,098
I hope you didn't chuck away any of the chassis!

(Although restoring the thing to working condition would have gained my approval!)
No, we stored the chassis (and even the fixing screws etc.), it's only a 'temporary' modification - and 'should' come back eventually. The Ecko cabinet came from one of the sets in our 'museum'.

As far as I know, the original set was in working condition when originally stored.
Nigel Goodwin is offline   Reply With Quote
Old 31-07-2013, 12:16
poppasmurf
Forum Member
 
Join Date: Aug 2004
Location: Arley, Worcs
Posts: 1,299
There was once an experiment on a BBC programme (I think it was Tomorrow's World but don't hold me to that) in the 1960's that showed 'colour' on a black and white programme. The effect was produced by the transmission of the programme being 'flashed' in a certain way, and it did work as I remember.

Maybe someone else can remember this experiment?
poppasmurf is offline   Reply With Quote
Old 31-07-2013, 16:20
anthony david
Forum Member
 
Join Date: Dec 2012
Posts: 659
There was once an experiment on a BBC programme (I think it was Tomorrow's World but don't hold me to that) in the 1960's that showed 'colour' on a black and white programme. The effect was produced by the transmission of the programme being 'flashed' in a certain way, and it did work as I remember.

Maybe someone else can remember this experiment?
I remember it and I remember seeing colours but they just psychedelic nonsense unrelated to what they should have been. The flashing was unpleasant as well.
anthony david is offline   Reply With Quote
 
Reply



Thread Tools Search this Thread
Search this Thread:

Advanced Search

 
Forum Jump


All times are GMT +1. The time now is 09:29.