Other 405 line colour receivers such as the GEC TT4 have a very prototype look about them. The Pye which are discussing is quite different, it's got the appearance of a series production set. A fair amount of investment must have gone in to making it. Perhaps they had the North American market in mind?
The colour sub-cattier frequency was finalised as 2,657,812.5 Hz. That's the line frequency fH X 525 divided by 2
Apart from three special valves which were imported from America, two 6BY6 and a 6BD4 the others are the common Mullard types.
Two parallel PL36 and two parallel PY81s are used for the extra power requirement from the line output stage. Three DY86 diodes are employed for the EHT. The circuit arrangement is not a voltage doubler. The line output transformer has a 17KV winding. This along with the 6KV pulse present at the anodes of the two PL36 produces the 23KV for the CRT. The focus voltage comes from the 6KV source. The HT supply for the line output stage comes from a voltage doubler employing two flat selenium rectifiers. These have been replaced with silicon diodes.
About 1960 Ekco made an impressive looking 405 line colour set. The only known example has been converted to 625PAL. The set looks like a enlarged model T330.
I often hear rumours of other 405 line colour TVs. We should track them down.
Till Eulenspiegel.
See page 17 for the USA NTSC specification and page 27 for the modifications required for a 405 system.
http://www.earlytelevision.org/pdf/Marc ... slides.pdf
Frank
Frank
That tube base looks familiar ...
It's from my homebrew monitor with DG7-32 CRT http://andydoz.blogspot.com/2014/09/simple-tv-using-dg7-32-scope-tube.html
I got the base from eBay seller "Michael's elctronics emporium" if memory serves.
The colour CRT base on the 21AXP22 has fourteen pins, the same number as later tubes such as the A63-11X.
Till Eulenspiegel.
The system used in these experiments was a variation of the NTSC system.
It's a pity that the APTS couldn't get the aspect ratio right! It looks as if it has been cropped to 16:9 and then shown at 4:3.
It would be interesting to know what is going wrong here. If you present YouTube with 4:3 material they do appear to present it more of less correctly but the BBC appear to be making a similar mess of 4:3 in recent times:
http://www.vintage-radio.net/forum/show ... p?t=122305
Peter
It's a pity that the APTS couldn't get the aspect ratio right! It looks as if it has been cropped to 16:9 and then shown at 4:3.
It would be interesting to know what is going wrong here. If you present YouTube with 4:3 material they do appear to present it more of less correctly but the BBC appear to be making a similar mess of 4:3 in recent times:
http://www.vintage-radio.net/forum/show ... p?t=122305
Peter
If you present YouTube with 4:3 material they do appear to present it more of less correctly but the BBC appear to be making a similar mess of 4:3 in recent times:
http://www.vintage-radio.net/forum/show ... p?t=122305Peter
"You are not logged in or you do not have permission to access this page" ??
10 posts required and be logged in to access that part of the site.
Frank
Frank
Okay; not a member, so...
Sorry, I won't reproduce the full thread. My initial post was:
Have just been watching a program about the Two Ronnies including lots of clips from their shows. These almost all date from the pre-widescreen era so the BBC fills the 16:9 with a full height image with static filler strips where you might expect to see black areas but do they present the vintage material with correct 4:3 format? No, for some strange reason they display it as 5:4 format making everyone look a little skinny!
Why?
Peter
After some slightly wandering discussion I posted:
I too have seen the BBC transmit 16:9 displaying a 4:3 image correctly with black bars so they can do it.
I just cannot understand why they choose to display 4:3 material as 5:4.
Perhaps it is pure ignorance or perhaps it is deliberate distortion of older material a bit like the nasty habit of adding noise or fake film scratches or strange colour casts.
Peter
The power consumption must've been phenomenal with a 50mm neck and all valves and I thought the B&O 3400 was high on power at 360w. How much power did these sets use?
Not as much as you think as the tube has a 70 degree scanning angle compared with the B&O's 110 degrees. The average power consumption for this kind of set was 350 watts.
That compares well with the the good old G6, weighing in at a healthy 500W! - No need for central heating in that room. 
Forgot to mention, B&O made a 'roundie' colour set as well in 1963, 625-lines of course and probably PAL:
Been to see this wonderful set today at Davids shop the build quality of this set is amazing considering it was an experimental set 60 years ago . Judging by the valve & component line up it would warm the room it was in took some photos will up load them soon
The Pye 405 colour set has two heater chains so that's 0.6amp drawn from the mains. 144watts! I'll count the valves later today, we do know that there is eight in the line output cage. Two PL36, two PY81, three DY86 and one 6BD4 stabiliser tube.
From the Radiomuseum: http://www.radiomuseum.org/tubes/tube_6bd4a.html This tube is similar to the ED500/PD500.
The EHT shunt stabiliser tube and CRT heaters are supplied from a mains transformer.
Under conditions of zero beam current in the CRT the shunt stabiliser will dissipate over 20watts. The anode can glow dull red.
There is a good deal of crystal diodes in this set, in fact there are no EB91 double diodes anywhere on the chassis.
Till Eulenspiegel.
The Pye engineers obviously had their reasons but I would have thought it would have been simpler for them to use valves from the USA that had been designed for the extra scanning/EHT power required for a CTV tube.
If it is possible to get it working I am sure you are the one to sort it out, I would have given up before starting.
Frank
Frank
Hi Frank,
I believe it was policy in those times to use as many UK sourced parts as possible. In the Pye the CRT and it's scanning components were supplied by an US maker which was most likely to have been RCA, quite simply no UK manufacture made these components at that time. The CRT mask was also supplied by an US firm. Philips in Holland might have started making colour CRTs in 1961/62, perhaps earlier?
Some elements of the Pye receiver's circuit originated from the 1955 model VT17. The tuner and IF amplifiers , also the line oscillator and frame timebase.
The experimental Bush colour set employed a pair of PL300 valves for the line output. The set was designed as a 625 line receiver from outset. Confirmation required for that fact.
Murphy made a 405 line colour receiver. Also Ekco before the company was taken over by Pye.
An article about the GEC TT4 can be found in the Practical Television magazine.
Till Eulenspiegel.
I believe it was policy in those times to use as many UK sourced parts as possible.
Till Eulenspiegel.
Import taxes were probably prohibitively high.
I can understand the RF/IF sections using tested UK designs but refined to reduce phase distortion and adequate band width. The UK and USA RF/IF sections needed different criteria, I don't mean frequency/bandwidth but the USA sets needed to have good sensitivity with good intermodulation characteristics, i.e. the set had to perform well in deep fringe as well as large conurbations that had many stations filling up the VHF bands. UK sets generally required just good sensitivity as the transmitters were few and far between and even then some TV's were not as sensitive as others.
I had not heard of the PL300, I have been out of the trade so long I have lost most of the knowledge.
Frank
Frank
The PL300 was developed in France by Fivre in 1961. Mullard marketed the valve in the UK. That's why I believe the Bush colour set which uses the PL300 is a 625 receiver. By that time we all knew the game was up for 405 and any further development of a colour TV system using the old line standard. The future was 625.
The PL300: http://www.radiomuseum.org/tubes/tube_pl300.html
Till Eulenspiegel.
Hi, from RR. What sort of EHT system did these old 405 colour sets have? did they have a multiplier using DY86's or something similar or did they have a full overwinding like some later colour sets? Did any of them have a LOPT in a can of oil like on the old Murphy "oily beasts"? What sort of EHT voltage did they use? RR.
Hi RR, The Pye 405 line colour set we are discussing employs three DY86 diodes in what is not strictly a double circuit. The EHT over winding on the transformer provides 17KV which is augmented from the 6KV pulse present at the anodes of the two PL36 output valves to produce 23KV. It's the same arrangement is used in the RCA 21CT55. The 21CT55 was developed from the CT100, the first RCA colour TV.
EHT boosters were used on much earlier sets. For example the post war HMV model 1804. When it came to replacing the original Emiscope 3/4 CRT, the TA10 was the replacement. This tube required more EHT, the mains transformer supplied only 4KV. The answer was an EHT booster which used the 1-5KV pulse present at the anode of the line output valve to augment the existing 4KV. You got 5 to 5.5KV.
I'm certain that the DY86 valves are really not up to the job. Maybe something more like this: http://www.radiomuseum.org/tubes/tube_3a3.html Used in American colour TVs.
The DY86: http://www.radiomuseum.org/tubes/tube_dy86.html
The DY802 could be considered.
Till Eulenspiegel.
