UK Colour 405 line to RGB adapter wanted.

[audion_1908]

Hi all,

Is it possible to use a 625 line PAL composite to RGB adapter on UK 405 line colour? maybe something like this: http://www.howtoconvert.co.uk/howcomp2rgb.htm

As I want to use a 405 line monochrome Bush TV43 for colour and 3D by using a system like the Col-R-Tel adapter sold in the 1950s in the USA that allowed colour viewing on a monochrome TV, but using a spinning colour disk on a head mounted 3D-Imager, like the Vectrex 3D-Imager in 1982:
http://old.madtronix.com/html/3d_imager.html

What is the differences between UK colour 405 line and 625 line PAL?

Thanks.

[Andy Doz]

There was no UK 405 colour services, other than experimental. It was based on NTSC.
To recover this colour info with a colour wheel is going to be a difficult task.

[Andy Green]

Not impossible, there was an article in Wireless World in the 70s that I used to have that described a PAL to colour wheel converter, it would however require a lot of work and a good knowledge of video circuit design. There is a version Aurora standards converter that converted 525line NTSC to CBS sequential colour. Maybe build a replica of CBS set and use one of these?

[emeritus]

You can find information about the 1954 experiments with 405 line NTSC here: http://www.earlytelevision.org/british_ntsc_color.html

It includes a Marconi booklet containing the technical specs of two alternaitve Marconi proposals that were demonstrated to the public in a closed circuit demo prior to the BBC's experimental broadcast transmissions.

The site also has an account of the restoration of a Pye colour receiver for the experimental UK 405 NTSC standard.

[audion_1908]

It looks like I will have to do a lot of reading.
I have a raspberry pi that I want to use as the video source, it that can do composite ntsc and pal but not 405 lines at the moment, but I could get an Aurora standards converter.

it looks like my choice is
British Experimental Field Sequential Color System
or British Experimental 405 line NTSC Color System
or British Experimental 405 line PAL Color System
but it has to look ok on my Bush tv43, I will look up the bbc trials of 405 line ntsc color with monochrome 405 line tvs.
I can get the circuit for the US 525 line NTSC Col-R-Tel adapter that I may be able to modify for 405 lines. I dont mind making some mods to my bush tv43, but they would have to be easy to reverse.
are there any pal or ntsc decoder chips that will work on 405 lines and output RGB and sync like the NTSC Col-R-Tel adapter?

I think Kat has done some quite spectacular stuff with a bog standard TV card and Linux. Here's a start https://www.vintage-radio.net/forum/...ghlight=mythtv

[julie_m]

Last I checked, the Raspberry Pi couldn't do the exotic modelines needed for 405 line TV. You need a graphics card with fully Open Source drivers -- forget anything that uses binary blobs.

[Kat Manton]

Actually, I was using the nVidia binary driver; I've never used the open-source one as, if I recall correctly, it lacked support for decoding MPEG-2 in hardware. Unless any further progress has been made, forget the open-source driver.

But yes, if you want a source of 405-line RGB video, a PC with an nVidia graphics card (tested: FX 5200 and GeForce 4) and DVB-T card; with Linux, the binary graphics driver from nVidia, and MythTV installed and a custom X modeline will get you that. And several other obsolete standards, including RGB output of CBS field-sequential, which I'd argue would be a better choice if you're planning on experimenting with a mono CRT plus colour-wheel system, due to the high field rate.

[audion_1908]

I want to use the Raspberry Pi as I want to put it inside my Bush TV43. I was thinking of maybe using an external USB graphics card, but I don't think they are full graphics cards? Can they do 405 lines with MythTV?

I will have a look at USB TV out cards. Can a UK or US one do 405 lines?

[Kat Manton]

I have no idea if a USB card would work, I've never owned one. Incidentally, I used the VGA RGB output as it proved impossible (or at least non-trivial) to program the scaler used for the TV out for anything other than 525 and 625.

If you try anything other than the older AGP/PCI nVidia cards I've already worked out modelines for, you'll have to see if there's an open-source driver for it, then examine the source to find out how the dot-clock frequency is programmed. Then you can determine the specific frequencies the dot-clock can be set to. Knowing this (and other limitations of the card, e.g., the line length has to be a multiple of 8), it's then possible to work out X modelines which produce correct timing (and usually a somewhat odd resolution, but that doesn't matter when using MythTV.)

(You can specify any dot-clock frequency you like in the config file; however, the driver will set the actual dot-clock to the closest frequency the card's capable of. This isn't a problem when using a computer monitor; it is when trying to generate an obsolete TV standard with correct timing.)

[jhalphen]

Hi Audion_1908

Have a look at this section of the ETF web site:

"Building your own homemade color converters":

http://www.earlytelevision.org/homem...onverters.html

Happy reading!

Best Regards

jhalphen
Paris/France

[audion_1908]

It looks like the US Experimental Field Sequential Colour System is 405 line

[Kat Manton]

Yes. 405-line, with 29.160kHz line rate and 144Hz field rate. In other words, the only thing it has in common with the UK standard is the number of lines. (You can see my 2006 experiment, where I managed to generate RGB video with approximately the right timing as a 'proof-of-concept' here.)

[FERNSEH]

The Motorola MC1377 PAL/NTSC encoder IC can be adapted for 405 line NTSC.
The application notes describe how to make a colour bars generator for NTSC525 and PAL 625. With some changes to some component values the chip will operate as a 405NTSC encoder for the colour bars generator.

DFWB.

[audion_1908]

I am working hard on getting the Bush tv43 working first, then I am going to have some fun with it!

[Nicklyons2]

The 405 line colour system is, sadly, an almost forgotten backwater of British TV history. A colleague in the early 1970's worked on one of Bush's experimental 21" round tubed sets made for this standard, (oh to get hold of this now!). Leeds Polytech (Now Metro University) used to run engineering training courses for the IBA and had, in their armoury of equipment to practice on, a very early Rank Cintel machine which had a 405 line NTSC encoder.

For further info on this era try: "BBC Engineering Monograph No.18" May 1958, which outlines the basic spec and results of tests, G.C. Gouriet "An Introduction to Colour TV" 1955 pub. The Television Society/Norman Price, & Peter Swift, G. Boris Townsend "Colour Television:NTSC system principles & practices" 1961 pub. (I think) Iliffe. I've got a photocopy of the Monograph (around 40 pages) if you can't find it elsewhere,
Cheers, Nick

[Nickthedentist]

Originally Posted by Nicklyons2

oh to get hold of this now!

There are some survivors, see here: https://www.vintage-radio.net/forum/...ad.php?t=68780

[Nicklyons2]

What can I say - they're just fabulous - 'proper' TVs; and thanks for pointing me to them,
Nick

[audion_1908]

You can see how my 405 line Bush TV is going at https://www.vintage-radio.net/forum/...ad.php?t=92727

[audion_1908]

Would feeding a uk 405 line black and white tv colour signal degrade the picture? if such a video source could be cooked up, MythTV?