B&w console front glass
 

Does anyone know why the safety glass on the front of an old b&w tv is so dark, is it to shield from radiation ? It overall darkens the brightness of the picture it's like it defeats a nice bright picture output. :smoke:

Maybe it needs cleaning.

It's tinted from factory.

Some are dirty from dust others are tinted on purpose.

Purpose tinted safety glass is to prevent glare from room lighting. Glare reflected off the CRT face is attenuates twice as much (coming in through the tinted safety glass and leaving through it) as the CRT image light... But what about the light reflected directly off the outside of the safety glass it's self you ask.... usually the safety glass is tilted down so reflections off the safety are aimed at the floor and not up at the viewer and or the glass is frosted to reduce reflectivity.

The glass is tinted to make the blacks blacker and improve the contrast.
The unlit phosphor is not very dark, so room light makes it show brighter than ideal.

I remember one B&W manufacturer (Hoffman?) which had a yellowish tint to its safety glass kind of like those "night vision" glasses they sell on late night TV shows.

What was behind this unusual tint? Was it really easier on the eyes?

Hoffman (Qu)Easyvision was just marketing Tom Sawyering the public to think the cheap green war surplus glass manufacturing was saving on was somehow a feature....It didn't offer any real improvement or detriment just was something different.

There are some posts around here somewhere that say the urban legend is that Hoffman got a deal on some war surplus tinted glass.

The tinted sets were marketed as "Easy Vision."

Well I'm just going to get a clear sheet of glass cut to size and call it done.

I don't think I would just get ordinary glass. The safety glass is there to protect you from flying glass should the CRT implode. Supposedly, the electron gun can come at you at a high rate of speed if the CRT implodes in a certain manner.

Hoffman notwithstanding, all the manufacturers had to pay extra for that tint so it must have done a good job. In the color era, when brightness was paramount, the higher end tubes had tinted faceplates and even frosted.

I think the separate safety glass is more to break the impact and prevent implosion than to protect you if it does implode. This means that high strength glass is still desired over ordinary window glass.

Tempered glass would be preferable. If you find an old coffee table top, you could probably find somebody to cut it to size. I suppose the easiest route would be to get a piece of 3/8" thick plexiglass, or however thick the original glass is. Matter of fact, in lieu of tempered glass, a sheet of thick plexiglass with a sheet of 1/8" regular plate glass in front of it would protect the tube from impacts and protect the plexiglass from getting scratched.

Also I don't think Hoffman Easyvision sets were actually green phosphor. Just yellow safety glass.

When we were kids, we used to watch TV in the dark because the picture was so improved for that very reason. Of course, mom used to yell at us because "it will hurt your eyes!"..

Sylvania, somewhere about 1980 or so, came out with the Superset. These TVs had a very dark tinted faceplate and had a spectacular picture. These TVs had a beautiful black level. Unfortunately, in order to correct for low brightness, these tubes were driven hard and died early.

Side story: back in the early 70s, my dad used to buy RCA all-new Hi-Lite 23" and 25" tubes for CRT replacements, but also stocked a low end rebuilt tube named "Maverick".

The Mavericks were the economy line and dad used to give customers the option of price. The Maverick's were bright, sharp, and reliable and had excellent purity, but they had the oddest light colored phosphor - sort of a greenish white. I mean, when the TV was off it looked weird. Back then, I couldn't understand why they picture was odd. No matter what I did with the contrast or brightness, I couldn't get a normal picture. Of course, it was the light colored phosphor. It didn't occur to me at that time that the darkest image on the screen couldn't get darker than the unlit light color phosphor.

John

Can't resist! :D

https://coub.com/view/4q8to

:lmao: classic Monty Python.


I own a late 40s Hoffman (qu)Easy Vision set and can confirm it is a normal P4 phosphor CRT with a separate plate of greenish yellow safety glass in front of it.


A decent part of the darkening of 70s color CRTS was black matrix technology. In 1969 or 70 Zenith released the first black matrix "Chromacolor" CRT (within 2-3 years marketing had muddied the meaning of the trade name Chromacolor to make you think it had something to do with the chassis). The black matrix concept was to lay down a grid of black light absorbing material on the inside of the screen such that it would cover the space between the phosphor dots and give multiple benefits....it would absorb room light darkening balcks and improving contrast it also achieved benefits in focus and convergence as well as brightness...the black non light emitting border meant the shadow mask hole guard band could be inverted such that the beam would light the entire surface of each dot. Older tubes had nothing between each phosphor dot so to prevent purity errors (one color gun hitting wrong color phosphor) the shadow mask would block the electron beam such that it only hit and lit the center of the phosphor dot only partially lighting the dot (which would be dimmer than black matrix lighting the entire phosphor dot). Initially the Black Matrix technology was Zenith only but it gradually spread throughout the industry in the 70s.

Some color phosphor mixes (sulfide IIRC) were greenish by formulation, others had a greenish tinted safety glass... Zenith in the early to late 60s painted their screen bezels a light green and often ordered the safety glass tinted the same color to match...It is probable a number of rebuilders used that tint since almost half of TVs were Zeniths (Zenith and RCA evenly split an 85% market share back then).

In the early 60s GE mixed their phosphor so their monochrome CRTs would appear sky blue when powered off...I have a 1962 new car model year issue of look magazine that has a GE add describing this. In the 80s Mitsubishi did this on color TVs too.

Another advantage of "negative guard band" (illuminating the whole dot) was the total elimination of white field purity problems. In the old tubes, even if the individual red, green, and blue fields were pure, errors in beam landing meant the beam could land on a more or less efficient part of the phosphor dot. If this was different for each primary color, the resulting white would be slightly off-color in some part of the screen. The 21AXP22 in my CTC-5 shows this problem.

Zenith had to go to court to defend its advertising of the advantages of black matrix tubes - they were sued by other manufacturers claiming that Zenith's statements were unfounded, but Zenith prevailed.

Much later, RCA introduced tinted phosphors. Each color of phosphor was tinted its own primary color so that reflection of the other colors was reduced. When you examined the face with a magnifier and the set off, you could see that each dot (or line, for in-line tubes) was tinted.

Interesting about.RCAs tinted.pbosphors...I've.seen CRTs with that before but never knew why that was done.

GE also offered a "blue" crt in the 80's on high-line color sets. I have a brochure somewhere that I should scan; they called it Neovision. I seem to recall it was a hard sell because it looked so different. I think their TV commercial made light of that fact.

I had also noticed the color of phosphor stripes on some unpowered sets. Something else I learned today!

Here in Germany they wanted to make us believe, that tinted glass raise
the contrast when sunlight will shine on the screen.
But it was closeby only said in 1959!
Before and after there were only a few sets with tinted glass!

The truth is, that you have to light up the CRT stronger for better
viewing thru the tinted glass.
My experience with tinted glass TVs goes in the direction, that they
have more weak tubes than sets without tinted glass!

Regards,
SIXMILLION DOLLARMAN

That was true in the first few years here in the States. Sylvania had a big problem right after they introduced the Superset which had a very dark safety glass (looked almost black). That TV did have spectacular blacks though.

By the early 80s, the short life problem went away. My father in law still has the RCA CTC169 ColorTrak 2000 that I sold him in 1992. He uses it every day. That tube is as strong as the day he got it.

John