Porthole Designs - Videokarma.org TV - Video

Konrad Schiecke · #1 08-19-2008, 12:58 PM

I am completing restoration on my first porthole set,a 7" Tele-Tone. I assume that the vertical does not fill the screen and is only scanned vertically to maintain the transmitted aspect ratio of 1:33 to 1,correct?. The porthole opening was only a cosmetic issue with manufacturers except for Zenith which allowed the vertical to be scanned to the top and bottom with the push of the button, correct?
Appreciate any comments from porthole tv collectors.
Konrad

Phil Nelson · #2 08-19-2008, 01:58 PM

With all round CRTs, you have a choice. If you expand the vertical and horizontal to fill the round CRT and maintain the correct aspects, you lose the corners of the picture. If you reduce them to show the entire picture, you are not using the entire CRT (there will be black bars at top and sides).

Many round-CRT sets, like my Hallicrafters 505 and National TV-7W, put a rectangular mask in front the CRT, so the displayed portion is rectangular, even though the CRT is round.

If your set shows the entire CRT without a rectangular mask, then I guess it's a matter of your preference. You can usually adjust the width and height to make it work either way.

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Konrad Schiecke · #3 08-20-2008, 12:45 PM

Hi Phil, Thanks for your comments.I have 12 sets, mostly 7" ,with round tubes that mask the CRT to a 3X4 aspect ratio. What I was looking for was an insite to what manufacturers did when they shipped a new porthole set. Most manufacturers vertical circuits cannot supply a linear scan to fill a 7" CRT.
I believe that the porthole Bezel was a styling issue. But then again in todays word when you rent a tape which is wide screen (1.85 to 1) or scope(2.35 to 1) a lot of people get mad when they see a black top and bottom on there 3X4 aspect ratio sets. So whats the answer to how porthole sets were shipped ? I did not start my tv design career till about 10 years after the porthole sets came and went. My parents set was not a porthole but a 16" rectangular Sentinel console. So for those folks that had porthole sets when they were growing up what do your memories tell you?
Konrad
.

Tony V · #4 08-20-2008, 06:26 PM

It would seem to me if the tv has the capability to adjust the picture to fill the screen and be proportionate then it would be best to do so. The reason i say this is to keep the crt from having phosphor burn around the edges.
-Tony

Sandy G · #5 08-20-2008, 06:49 PM

I would agree w/Tony...both times ! Seriously, looks like the image would be a tad distorted to make a 3X4 image fit a circle, anyway...

***Eric H*** · #6 08-20-2008, 09:33 PM

I've always operated on the assumption that if they built it as a porthole then they intended it to fill the screen otherwise they might as well have masked it.
This also gave them an edge in the number of square inches they could claim.

bgadow · #7 08-20-2008, 09:46 PM

I recall seeing an ad for a Zenith porthole that had a switch on the front that automatically changed the size; I'm not sure how common the feature was. Then there was the Westinghouse that had a mechanically adjustable mask-I'm not sure if there was a switch for the size to go with it or if you just adjusted the height. Every porthole advertisement I've seen showed a full-view round picture.

*Bill Cahill* · #8 08-21-2008, 03:00 PM

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ChrisW6ATV · #9 08-22-2008, 12:42 AM

Quote:

Originally Posted by bgadow

I recall seeing an ad for a Zenith porthole that had a switch on the front that automatically changed the size; I'm not sure how common the feature was. Then there was the Westinghouse that had a mechanically adjustable mask-I'm not sure if there was a switch for the size to go with it or if you just adjusted the height. Every porthole advertisement I've seen showed a full-view round picture.

My 12" Zenith and 10" Stromberg-Carlson both have a switch to change from proper aspect ratio to a filled round screen. I know the Zenith's (unmarked) switch worked properly when I had done repairs on it years ago, but now I need to do a complete restoration on the set before powering it up again.

Sandy G · #10 08-22-2008, 01:17 AM

I STILL want me a "Claridge" model Zenith, sometime...It is just SO "1950" looking. I don't mean the decade of the Fifties, I mean the YEAR "1950"...It's kinda like the 20th century started over again in 1950, got rid of all the horse 'n' buggy nonsense, & became the 20TH CENTURY...Does any of this make sense to anyone besides me, or am I just fundamentally weird ?!?

*Bill Cahill* · #11 08-22-2008, 09:14 AM

Quote:

Originally Posted by Sandy G

I STILL want me a "Claridge" model Zenith, sometime...It is just SO "1950" looking. I don't mean the decade of the Fifties, I mean the YEAR "1950"...It's kinda like the 20th century started over again in 1950, got rid of all the horse 'n' buggy nonsense, & became the 20TH CENTURY...Does any of this make sense to anyone besides me, or am I just fundamentally weird ?!?

Well, I guess that depends. In a sense, we all are "fundamentally weird".
Now, my 1950 RCA Victor 6T74 actually does look like a 1950 tv with a design towards the Regency period, as intended by RCA, hence, the name of the cabinet style, Regency.
Magnavox, on the other hand, seemed to have Four case styles they called Regency.

Being that my Stromberg Carlson is a double D mask, Id doesn't have that switch.. That switch was put only on round screen sets in case the owner wanted a square picture, instead of round.
See the ads.
I didn't know SC even made any completely round screen sets.
I'm getting a round picture tube SC, but, it has the usual double D mask.
I once had a 24" SC, but, here, again, it was double D.
Bill Cahill

Tube TV · #12 08-23-2008, 06:04 AM

Im going to take a stab at this .

I would say that most of the porthole sets would have had the picture filling the whole CRT face . If not some early TV buyers might have thought it to be defective compared to a masked set .
Also , the sync pulse lines at the top and bottom of the screen might have been annoying .
I still don't have any porthole sets , but if I did I would run them full screen also .

John Marinello · #13 08-23-2008, 09:32 AM

I didn't know SC even made any completely round screen sets.
Bill Cahill[/QUOTE]

They sure did!

*Bill Cahill* · #14 08-23-2008, 09:33 AM

Now, I will try again.
I have original ads for Zenith round screen tv's. The ad clearly shows all the tv's with a full round picture. Zenith, and, several other companies thought a totally round picture would be more pleasing.
Later, Zenith offered the electronic switch as well to appease customers wanting a square picture because they thought a round picture would lose some of the video. Actually, both did.
Bill Cahill

Ampico-kid · #15 08-23-2008, 02:43 PM

Hi;
I just thought I'd chime in on this one.

Here's a picture of the "normal" test pattern screen image taken from the service manual of my 1951 Zenith Porthole set. I'd say the picture is anything but normal. The images are flat on top and flat on the bottom, and stretched in the middle.

Zenith does have a switch that allows the viewer to change the picture dimensions to a more well proportioned image, but doing so leaves a 2 to 3 inch dead area on the top and bottom of the screen.

Just thought I'd throw in my two cents.

Thanks.
Bob.