405 colour on my Pye CTV - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

FERNSEH · 7th Nov 2017, 11:26 am

I'm busy reassembling the scanning coils, as long as there are no interruptions in the shop all the CRT neck components will be refitted today.
Reference to the April 1956 Wireless World, page 185. The Mazda 6P1 frame output valve receives it's anode supply from the 400 HT rail.
Pye must have invested a lot of resources into developing this set because unlike other UK made CTVs it doesn't have that "prototype" look about it.

DFWB.

FERNSEH · 7th Nov 2017, 9:38 pm

In fact the frame output stage does already receive it’s HT via a 3.3Kohm resistor from the 360 volt supply. According to my notes the decoupled HT supplied to the transformer primary is 290 volts. I’ll take a chance and short out the 3.3K resistor and supply the frame output stage with the full HT. Let’s see what happens.

DFWB.

FERNSEH · 7th Nov 2017, 11:56 pm

Played safe and connected a 2.7Kohm resistor across the existing 3.3Kohm frame timebase HT supply resistor. Sure enough there is a slight improvement to the linearity but mainly at the top of the picture. Also, there is plenty height available now before the picture cramps at the top. See second attachment.
Also noted is that the HT voltage is only 320 volts, and that's the voltage measured a the anodes of the two PY81 booster diodes. I reckon I should hit the frame output stage with the full 320volt HT supply.

DFWB.

cheerfulcharlie · 8th Nov 2017, 12:38 am

Quote:

Originally Posted by 1100 man

Hi David,
Well that is interesting!! As far as I was aware, The BBC was considering the use of NTSC in the early '60's, but I didn't know that anyone in the UK was doing anything as far back as '56.
Is this a UK production set or a prototype? In the event, it would have been totally obsolete by the time colour actually started in (I believe) 1967!
It would be great to have some more details/ pictures etc. of the set or a link to an old thread if you've already done that. Circuit details would also be very interesting.
Good Heavens, colour in 1956: whatever next!!
All the best
Nick

The BBC actually did a colour link from the E2 Coronation to the Great Ormond Street children's hospital.

An ITV series 'Adventures of Sir Lancelot' in the 50s had some of the episodes made in colour and these vary in their presentation (although these may been corrected these days for the DVD) as because in both here and the US they were using the show to experiment with different film makes and grades that they could use on a CTV system.. they discovered that Technicolor was a big NO NO as the contrast ratio was just too vast for early equipment to cope with...consequently any film you saw on TV in those days that said it was 'Technicolor' was actually a TV spec Eastman mono/colour print.

FERNSEH · 8th Nov 2017, 10:28 pm

One of the three heater chains has gone open circuit. It's the chain that supplies the valve heaters of the receiver section. Will investigate and report back later.

DFWB.

emeritus · 10th Nov 2017, 10:17 pm

The extract from a BUSH TV leaflet from early 1952 (undated, but it refers on an unscanned page to a TV22 that was expected to be the cheapest TV exhibited in the forthcoming Manchester exhibition of April 1952) suggests that, at that time, UK TV manufacturers were concerned that people might be delaying buying new TVs in anticipation of colour, the BBC's colour TV transmissions then being expected to start in 4 year's time, ie circa 1956. Interesting that it refers to UK manufacturers knowing all about colour before the Americans! Could they be referring to Baird's experiments?

Re Pye, closed circuit colour TV is mentioned on the last page of an undated leaflet about their (black and white, Image Orthicon tubed, as used in their Type 2014 camera) underwater camera. I think it may date from circa 1952-54. The article in the link below refers to the prototype camera (made by Marconi) having been used by HMS Reclaim in 1951.

http://arl.g3w1.com/arl_underwater_viewing_systems.htm

This suggests that Pye's closed circuit colour TV system was a well established product by the time Pye's production underwater camera was produced.

peter_scott · 10th Nov 2017, 11:02 pm

I suspect that rather than Baird's two colour systems they were more likely to have in mind the field sequential systems with add-on colour filters offering fully compatible transmission for existing sets.
Leastwise the colour television system depicted for the public in a children's encyclopedia that I had in the 1950s clearly showed field sequential.

Peter

7th Nov 2017, 11:26 am	#21
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: 405 colour on my Pye CTV I'm busy reassembling the scanning coils, as long as there are no interruptions in the shop all the CRT neck components will be refitted today. Reference to the April 1956 Wireless World, page 185. The Mazda 6P1 frame output valve receives it's anode supply from the 400 HT rail. Pye must have invested a lot of resources into developing this set because unlike other UK made CTVs it doesn't have that "prototype" look about it. DFWB.

7th Nov 2017, 9:38 pm	#22
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: 405 colour on my Pye CTV In fact the frame output stage does already receive it’s HT via a 3.3Kohm resistor from the 360 volt supply. According to my notes the decoupled HT supplied to the transformer primary is 290 volts. I’ll take a chance and short out the 3.3K resistor and supply the frame output stage with the full HT. Let’s see what happens. DFWB.

7th Nov 2017, 11:56 pm	#23
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: 405 colour on my Pye CTV Played safe and connected a 2.7Kohm resistor across the existing 3.3Kohm frame timebase HT supply resistor. Sure enough there is a slight improvement to the linearity but mainly at the top of the picture. Also, there is plenty height available now before the picture cramps at the top. See second attachment. Also noted is that the HT voltage is only 320 volts, and that's the voltage measured a the anodes of the two PY81 booster diodes. I reckon I should hit the frame output stage with the full 320volt HT supply. DFWB. Attached Thumbnails Last edited by FERNSEH; 8th Nov 2017 at 12:26 am.

8th Nov 2017, 10:28 pm	#25
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: 405 colour on my Pye CTV One of the three heater chains has gone open circuit. It's the chain that supplies the valve heaters of the receiver section. Will investigate and report back later. DFWB.

10th Nov 2017, 11:02 pm	#27
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: 405 colour on my Pye CTV I suspect that rather than Baird's two colour systems they were more likely to have in mind the field sequential systems with add-on colour filters offering fully compatible transmission for existing sets. Leastwise the colour television system depicted for the public in a children's encyclopedia that I had in the 1950s clearly showed field sequential. Peter __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos Last edited by peter_scott; 10th Nov 2017 at 11:14 pm.