Comparison of display images of 6 vintage TVs:

I have restored 6 vintage Televisions and I thought it would
be interesting to compare the display quality of each of them.

All the below images were "over the air" reception using my
Blonder Tongue agile modulator.

1951 Zenith Porthole 24H21, 19" 19AP4 CRT:

The CRT is a little weak. Takes several minutes for the CRT to fully
light up and display an image.




1950 Zenith Porthole 24G26, 16" 16EP4 CRT:

This is my first restoration and definitely my favorite.
The CRT is not as weak as the above 19AP4.
It is not "aluminized".
Image is best viewed without direct sunlight entering the room.
Does not take as long after powering on for it
to display a viewable image.




1950 Raytheon Porthole 16AX23, 16" 16AP4 CRT:

The CRT was stone dead when I obtained this TV.
I had to rejuvenate it using my Sencore CR-70.
The brightness of this CRT is greater than the
two Zenith Portholes and definitely more viewable
in brightly lit rooms than both the Zenith Portholes.
I suspect a little more work and I can make
more improvements in its image display.




1949 Emerson 639, 7" 7JP4 CRT:

Pretty strong 7JP4 and the image display is much better
than the picture is depicting. It is definitely
my #2 top performer.




1949 GE Model 805 "Locomotive", 10" 10BP4 CRT:

My Sencore CR-70 showed that the Cutoff for the 10BP4 was not good at all.
Cutoff is supposed to give an indication of well the image
contrast is going to be. But, this TV is by far the top
performer of all 6 of these TVs.




1948 Philco 48-2500 Projection TV, 4" TP-400 CRT and Optics:

Very interesting TV. I find this TV really intriguing.
Image size is large but the image quality to be honest
really sucks - the worst of the 6. Not sure if its some
circuit issue, if there is an issue with the quality/adjustment
of the optical mirrors/lens, or if this is simply the way it
was in 1948.

Carl

Interesting, Carl.
Thanks for sharing.

Terrific eye candy, thanks for sharing!

You must be an "Amos 'n Andy" fan!

Those Porthole TVs do catch my attention - love Portholes.
Yeah, I can watch Amos 'n Andy videos over and over.
I've got a complete collection on DVD.

Carl

I'm not surprised the 10" GE is the best and the Philco projection set is the worst. That's what I would have expected given that most 10" sets have pretty sharp pictures, and I have never seen a projection set that had a good picture. I think the manufacturers sacrificed some quality to get the larger viewable picture on those. I have owned a number of them over the years but never kept one for more than a few years, and I also restored others for friends, but none of them were great performers. Out of all projection sets of that vintage, the RCA models usually work the best, but I couldn't stand to watch one for very long.

I would have expected the 7" set to be second worst, right above the projection set simply because these were entry level sets and not intended to be the top of the line in picture quality. Some do work surprisingly well though.

I think that the three porthole sets should all be relatively similar in operation, and all should be better than the 7" and nearly as good as the 10".

Have you ever checked resolution using a test pattern with wedges made up of lines, just as a comparison between the sets? It would be more accurate than simply looking at the received images.

Nice Carl! It makes me want more--vintage TV sets that is
Being on my second one I find myself comparing already.

The contrast is exceptional on my GE 805 TV - blacks are blacker, whites
are whiter. Just cannot achieve as good an image on the three Porthole TVs.
I hope over time to someday be able to obtain better CRTs for the Portholes.
It would be cool to have at least one of them to play as well as the GE 805.

The 7JP4 also has an exceptional display. You are not the only one
who has commented that the 7JP4's don't perform well. I guess I
got lucky with this one.

The Philco 48-2500 Projection TV has captured my interest. Would love
to have a benchmark as to how well it performed when new.

Carl

In the Philco 48-2500 thread where this first came up, the discussion started on the topic of "sharpness" and "focus." This thread brings up a few other image attributes that are very important to the perception of image quality:

- Brightness/Contrast: In the late 1940s, there were significant improvements in this area that make a big difference between earlier tubes and those coming after 1949 or so. CRT aluminization results in a much brighter picture, since it helps reflect any light emitted in the rear direction back out the front of the tube. Tinted glass was another important innovation. When tinted glass is used, the contrast significantly improves because of a darker black level. While tinting of course dims the bright part of the picture as well, it doubly dims the dark part of the picture, since room light must travel through the glass twice (first on the way to the phosphor, where it is scattered, and then once more on the way out). If you compare the picture on an aluminized CRT with tinted glass to one without either of those innovations, there is quite a difference in brightness and contrast. Sharpness, however, is the same. Even with a set turned off, you can tell immediately if you're looking at a more modern vs older CRT. Those that have a greenish off-white color are the old type, and will not produce a particularly bright, high contrast picture in a lighted room (they are best viewed with the lights low). Sets with a dark green or dark grey screen are the more modern type which will give a better picture.

- CRT size and beam spot diameter: Image sharpness is gauged in terms of how many "lines of resolution" can be produced (not scan lines, but vertical lines). This effectively takes the image size out of the way resolution is measured. If the electron beam spot were very small, a small CRT would be able to produce the same resolution as a large CRT. For a large CRT, for example 19 inch, a spot size of about 0.5 mm is small enough to resolve the maximum resolution that can be transmitted on a normal TV signal. For smaller CRTs, the spot size needs to shrink proportionally to maintain the same resolution. For example, for a 3 inch CRT, the spot size needs to be around 0.08 mm. It's not clear to me that this small of a spot size is actually achieved in small CRTs. It may be a matter of more than just the actual diameter of the electron beam -- scattering and "halo" effects in the phosphor also may play a role. Also, if the CRT is running at extremely high brightness, as it must in a projection set to make a bright enough picture after optical enlargement, the effective spot size may be larger than could be achieved at a lower brightness.

I believe the second point above may be one of the things limiting sharpness and focus on projection sets.

Thanks for sharing. That was interesting. I would have picked the projection to be the worst before seeing the images.

Before I recapped the Philco Projection TV, I thought the image would be
less sharp and clear as a glass tube but not that bad. Still wondering
what was the benchmark when these TVs were new. Like to hear from an
old timer who remembers when these sets were relatively new.

Also, the two Zenith Portholes utilize Zeniths "Blaxide" CRT stated in
one of their ads:
Zenith's amazing Blaxide "Black" Tube and the new "Super-Range" Chassis
bring you pictures of startling clarity and detail ... free from eyestraining
glare or blur even in daylight or fully lighted rooms!

The CRTs in the two Zenith Portholes are weak and 60+ years old. Like to
hear from an old timer who remembers when these sets were relatively new
for his opinion on how good the image was.

Carl

That name "Blaxide" sounds like marketing, for a "black side" CRT, in other words, a metal one. All of those fancy terms for various features in early electronics ("Golden Throat", anyone?) are amusing and interesting now. When the same thing still went on in the 1980s, though, I found it annoying or distracting. (What was "legato linear" in my Sony stereo amplifier?)

Thank you for posting the nice pictures, Carl.

The "blaxide" tubes had the faceplates etched, or frosted, to prevent specular reflection.
Only seen this done on metal tubes.

We had a Zenith porthole in the living room when I was a kid, my parents bought it new when they got their first house in the fall of 1950 so it was almost certainly a '51 model. It stayed around for several years and required frequent service. I remember that it had flyback failure which filled the room with a bad smell, lots of tube failures, and was overall not a great TV. My parents were on a first name basis with the local TV repairman, and I had to watch every move he made when he came to work on the set every few months. We always had the drapes closed in the living room when the TV was on because otherwise the picture looked washed out but it was sharp and clear if the room was dark. Around 1955 we got an Admiral 17" metal table model with an aluminized tube and it made the Zenith look very bad by comparison.

That is good information.
I love hearing remembrances about these old TVs.
Thanks for sharing.

Carl

From your pics to me it looks like the GE and Emerson were snapped in somewhat darker room conditions than the Portholes and Raytheon? Just saying that in those pics in particular, of course the screen is going to look a little extra washed-out just from the added room light especially with old light-colored screens from back then. I prefer to shut the curtains, kill the lights and dial the screen in for those conditions. Plus with too-bright a room, you can't always crank up the brightness all you want without starting to get retrace lines on a lot of sets.

Yayyy I have that exact Porthole console (your second one there) that I put in my mom's house in her bedroom. I even like watching my modern big screen TV in dark conditions, so is definitely a good idea with my two Portholes and Hoffman 600 sets. My table Porthole is brighter since a rebuilt 12lp4 was swapped in by someone in '63. My content preferences are The Honeymooners, The Stooges, I Love Lucy and Dick Van Dyke. : ))

The Raytheon looks like it has better focus / resolution than the portholes , maybe its just the pictures.

All nice sets
Mike

I've wondered about the Raytheon.
Maybe its CRT is stronger or maybe its circuitry.

Carl

I'm going to update my comparison of my 6 TVs.
I removed the DC Restore tube in the Philco 48-2500
projection TV and now rank it as my most viewable TV.
Removing this tube dramatically improved the video image.
There was a Philco Service Bulletin recommending to
remove this tube with the documentation for the Code 125
upgrade.

Certainly this TV does not have the clarity as the GE 805 but its
huge screen and great audio makes this TV very enjoyable.
Some of my focus issues is that I am not using the front surface
side of the Trapezoidal mirror as mine was quite cloudy.
Instead, I'm using the back side. I think getting the correct
mirror will improve the video further.

The video to me is best viewed about 10+ feet from the screen.
I can understand now its appeal when it was a relevant TV
back in 1948 - the screen size in a large room makes this
a very viewable TV. I have this TV at the door in my Garage
and my workbench is on the opposite wall 20+ feet away
and viewing from that distance is outstanding.

I think its really neat that the TV automatically powers on
when you lift up the screen.



Carl

Carl--I'm hoping you post a pic of the projection set when you get that mirror replaced. Hard to believe it's from'48!