Difference in Phosphor colour

[slidertogrid]

I have been sorting through the sets in my collection recently and getting them wired to a signal source so I can give them a run without having to heave them onto the bench. As I get older it seems someone is turning the gravity up each year!
I have two Philips 20" sets one single standard and the other dual standard. They both have very good tubes the bottom set has a Brimar tube which appears to be a replacement new tube rather than a regun. The top set has the original Red label Mullard.
There is a marked difference in the colour of the pictures the Brimar tube is very black and white whereas the Mullard has the usual blue tinge to the picture. The difference in more apparent than it looks in the photograph. I think it is the Brimar that is unusual. I have seen differences before but never this apparent, probably emphasised by the fact that the two sets are together.
I will have to check the label on the Brimar I wonder if it was a special tube made for monitors or the like?

[Amtec123]

Maybe stating the obvious but could it be that one tube is illuminant 'C' and the other is illuminant 'D'.

[Maarten]

The lower phosphor looks like a monitor grade phosphor that was called 'paper white' in computer monitors.

[Heatercathodeshort]

The Mazda tubes tended to have a bluish tinge that was liked by viewers. The later Mullard tubes tended to follow. The early Brimar/STC tubes from the 50s tended to have a slightly yellow looking phosphor when switched off but displayed a strong black and white picture.
The 210/300 series Philips did not use a Brimar tube originally. It would have been supplied with a Mullard A50-120WR. What is the number on the Brimar tube? I don't think they were producing their own domestic tubes as late as 1968. I have seen many later Brimar labelled tubes that are obviously Mullard particularly the bonded twin panel types from the early 60s. John.

[Maarten]

If a tube was produced by Mullard or another Philips subsidiary, it would carry factory stamps, not unlike those seen on receiving valves but larger. By 1968 those would likely be on the cone somewhere.

[slidertogrid]

Thanks for the info, that is interesting. I didn't realise there were such different screen Phosphors used in domestic tubes. I realised that screen colours had changed over the years but not that different colours were used at the same time. I didn't take a lot of notice of the Brimar label when I had the back off as at that time I hadn't noticed the unusual Phosphor colour. I will put the set back on the bench and have a better look at the label.

Both tubes look very good with good focus right into the corners despite both sets not having been run for some time. The 20" tube in the white A640 was more like what they are usually like after a long period of disuse with a bit of defocussing being worse at the edges when I first started using it, but after a prolonged run on 7.5 Volts it has come up a treat and looks very good now. ( He says keeping his fingers crossed! )

[Radio Wrangler]

The white light that our eyes are evolved to work in is thermal white noise, like that from a black body radiator at several thousand Kelvins temperature.

Individual phosphor chemical compounds give line spectrum light emissions. White is faked by using several line-emitting types of phosphor, where the intensities of the lines work with the selectivity of the colour filters in our eyes to give the impression of white. So even in monochrome things like B&W CRTs, fluorescent tubes, etc. the phosphor coating is mixed to produce a 'white' with the appearance of any desired colour cast or colour temperature. So the difference in whites is easily fiddled by mixing different proportions of the constituent phosphors. Trying the get the right red, the right green and the right blue for a colour CRT is much more difficult. I seem to remember it was the red which was usually the problem.

White isn't a natural colour for an LED, so the ones now common use a UV/Blue high efficiency LED and use a phosphor to make the other two components. Again, the apparent colour temperature can be fiddled with.

David

[Hartley118]

I recall back in around 1950 going with my parents to TV dealers to ‘help’ choosing our first TV. There were serried ranks of the various brands of B&W sets, and an abiding memory is of the surprisingly different hues of ‘white’. The eventual choice was a Pye FV1: its purple filter adds another variable on top of screen phosphor colour.

Martin

[regentone001]

years ago I had 2 Regentone Ten-17s when put side by side one had a distinct blue tint the other was pink. Both, as far as I know, had AW43 88 tubes which were original to the sets

[Amtec123]

Illuminant 'D' phosphor tubes were fitted in b&w TV studio monitors. Production, lighting, and sound galleries had a mixture of both colour and b&w monitors. When I started back in the early days of colour only the transmission and preview monitors were colour, all the others were b&w. These included the 4 or 5 camera's, VTR, telecine, slide scanner, and any external sources. When displaying a monochrome source the b&w monitors matched closely the colour monitors, assuming the colour ones had been correctly 'grey scaled'.