Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Jul Tue 29, 2014 11:52 pm


All times are UTC [ DST ]



Post New Topic Post Reply  [ 37 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: Why did they use round tubes for color so long?
PostPosted: Aug Fri 10, 2007 3:22 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 1948
Location: Laughlintown, PA
Just curious about why, long after b&w tubes went rectangular the color tubes were still round?


Top
 Profile  
 
 Post subject:
PostPosted: Aug Fri 10, 2007 3:59 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3218
Location: Poplar Bluff, MO USA
Well I'll make a few guesses, the early color gun assembly's were pretty big and required a larger neck on the tube, possibly it had to do with the attachment in the tube of the shadow mask and how to keep it stable, and without the corners on a rectangular tube the pincushion effect is not as big of a problem. The first rectangular tube that I remember being available was the 23EGP22, there was an earlier thread about all the problems and growing pains that went along with this tube. Toward the end of manufacture of round screen tube sets some think the companies were just trying to get rid of warehouses full of round tubes.

_________________
The older I grow the more I distrust the familiar doctrine that age brings wisdom.
KAØSCR


Top
 Profile  
 
 Post subject:
PostPosted: Aug Fri 10, 2007 3:59 pm 
Member

Joined: Jun Thu 15, 2006 1:21 am
Posts: 4021
Location: NE Ohio
Because of costs. RCA would have liked the round tube to hang around for quite a few more years so that they could have recovered more of their developement costs. Motorola changed all of that with a business relationship with National Video, a CRT manufacturer. They aiso had a vision. The 23EGP22 was a joint project and used a B&W bottle for the glass envelope. B'F.Goodrich was a national account and I was sent out to do the set up on a sample 23CK38 console for the BFG buyer (first set in Akron) and gee what's that bright purple glow in the neck of the tube. They had a lot of early failures but forced the industry into where it should have been. They had one production run where we had to change over half of the CRT's that the one store received. Hated to see Motorola leave the TV business though. They treated the buyer right and they are a great company. As an aside I had one manufacturer tell me that they did not beleive that any manufacturer made money with color TV.

_________________
Bruce


Last edited by Bruce Hagen on Aug Fri 10, 2007 7:56 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject:
PostPosted: Aug Fri 10, 2007 4:12 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 7784
Location: San Jose, CA USA
I always assumed it was because the mechanical stresses on a round tube are easier to manage. Any change in shape that would occur when fastening pieces together or letting things cool might adversely affect the alignment of the shadow mask to the phosphor dots. It took time for the industry to master the art of making non-round color tubes.

_________________
Tom K6VL


Top
 Profile  
 
 Post subject:
PostPosted: Aug Fri 10, 2007 5:15 pm 
Member

Joined: Jun Thu 15, 2006 1:21 am
Posts: 4021
Location: NE Ohio
Tom, Randy:

What you are saying is true but the public wanted the trimmer cabinets plus the transmitted picture was rectangular and Motorola had a vision and saw an opportunity. The early tubes did have convergence and purity difficulties but if it wasn't for Motorola we'd of been watching round tubes yet today. Well, maybe only into the '90's. :lol:

_________________
Bruce


Top
 Profile  
 
 Post subject:
PostPosted: Aug Fri 10, 2007 7:35 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 1948
Location: Laughlintown, PA
Clearly a big DUH! is indicated by me here...trying to recoup the initial investment - perfect answer! I guess (I hope!) I just didn't think of it long enough.

Tm


Top
 Profile  
 
 Post subject:
PostPosted: Aug Fri 10, 2007 8:40 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3218
Location: Poplar Bluff, MO USA
Bruce, I totally agree with you, silly me for not thinking of it being the biggest part of the equation. As someone once said "Always follow the Money".....

_________________
The older I grow the more I distrust the familiar doctrine that age brings wisdom.
KAØSCR


Top
 Profile  
 
 Post subject:
PostPosted: Aug Fri 10, 2007 9:03 pm 
Member

Joined: Jun Thu 15, 2006 1:21 am
Posts: 4021
Location: NE Ohio
Hi Randy:

RE: "follow the money" - stupid me, I didn't. I was told by those in the know, so to speak, to buy all the National Video stock that I could afford. Couldn't afford much so I didn't buy any. It was around $1, $2 and went up to over $100 - I think that might have been $200 as I really don't remember for sure. Anyway I missed my big chance. :(

_________________
Bruce


Top
 Profile  
 
 Post subject:
PostPosted: Aug Sat 11, 2007 2:24 am 
Moderator

Joined: Jan Thu 01, 1970 1:00 am
Posts: 8119
Location: Latham NY
This brings up my memory of buying my first color TV around1973, it was a Motorola works in a drawer set. I guess it was a 23" set, it was like having movies at home at the time. I had a huge antenna with a rotator on the roof (I worked for Radio Shack then) and that set got a great picture. It replaced my old RCA round 21" set that I got for nothing(had an open peaking coil) and I think it lasted about 10 yrs, not bad.


Top
 Profile  
 
 Post subject:
PostPosted: Aug Sat 11, 2007 4:38 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 553
Location: Columbus, OH
Remember that color TV sales were minimal until the late 60s, so there was not much reason for manufacturers (RCA sold the vast majority of sets) to come out with a rectangular tube.


Top
 Profile  
 
 Post subject:
PostPosted: Aug Sat 11, 2007 7:15 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3218
Location: Poplar Bluff, MO USA
The vast majority of new Magnavox Color sets that I delivered in the early 70's were the customers first color set. It was a really big and expensive deal. Most of the sets were financed for 2 to 3 years.
I usually brought the contract out for the customer to sign when I delivered the set. IIRC our 23" consoles started around 570.00 or so and went up from there, probably averaged about $750 for a nice console with remote control which added $100.00 to the price. A lot of money in 1970....

_________________
The older I grow the more I distrust the familiar doctrine that age brings wisdom.
KAØSCR


Top
 Profile  
 
 Post subject:
PostPosted: Aug Sun 12, 2007 8:41 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 718
Location: Littleton, CO USA
A number of things needed to come together for a total changeover to rectangular tubes.

1. The glass manufacturers had to provide a supply of rectangular blanks.
2. The CRT electron gun suppliers had to get up to volume
3. TV Assembly plants had to change over CRT handling and chassis testing facilities.
4. Round Tube Color TVs were selling well so there was no urgency.
5. All the other parts suppliers needed to gear up to provide the necessary quantities.
6. All the other deflection and mounting parts suppliers had to get up to speed.
7. Most manufacturers were still making RCA look-alikes.
8. Service personnel were still learning color.
9. Dealer service departments needed to buy more parts and another test fixture.
10. Cabinets had to be redesigned and provided in quantity.
11. Factories did not want to run two types of TVs at the same time.
12. Early rectangular tube yields were not up to expectations.

As with most technical products, it is a considerable distance from the research lab to the shipping dock. The engineers were not satisfied with all of the technical solutions. CRTs could overheat from too much high voltage and necks would crack. The heater currents were lowered to reduce heat. This required more efficient electron guns. High voltage regulation was improved. Every new part pushed back on a supplier that had to make a major component change. Often there were not enough parts to supply every manufacturer so those that shared development and/or tooling costs got priority.

There was no CAD or FlexTronics. The engineers who designed the product had to get it through the factory and out the door so they were conservative. It was not a conspiracy to withhold the rectangular color sets from the market. Rather, it was everyone coming together that enabled it to happen when it did.


Top
 Profile  
 
 Post subject:
PostPosted: Aug Mon 13, 2007 2:15 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 240
Location: Somerset, NJ USA
One major problem was pincushioning correction. Remember, in a round tube, the distance from the guns to the sides of the tube is equal all around the diameter of the tube face. In a rectangular tube, beam landing problems/convergence would be greater in the corners. Correction in a monochrome tube is simple....a couple of magnets mounted to the yoke. In a color tube, the problems are magnified. I remember some trade magazines of the early 60's, discussing this topic in great detail. It took quite a bit of engineering before a practical rectangular tube/chassis was made available. The 23EGP22 was a horrible tube which, thankfully, did not last very long. Magnavox (Magicbox), Admiral and Motorola were a few of the companies that used the 23EG. Zenith and RCA did not. They jumped right over to the 25" line of tubes.


Top
 Profile  
 
 Post subject:
PostPosted: Aug Mon 13, 2007 7:41 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 75
Location: Hollywood Hills, Ca.
It should be noted that Westinghouse briefly marketed a 22" rectangular color tv in the 1956-57 model year. The tube was designed by CBS-Hytron. The major drawback of the tube was edge convergence problems. Several models were offered and few survive today. A photo of this color receiver can be found on my site.

-Steve D.

_________________
Check out my vintage color tv site: http://www.wtv-zone.com/Stevetek/


Top
 Profile  
 
 Post subject:
PostPosted: Aug Mon 13, 2007 1:49 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 1421
Location: Naples, FL USA
That link does not work...

_________________
We improve things by making them worse...


Top
 Profile  
 
 Post subject:
PostPosted: Aug Mon 13, 2007 5:50 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 75
Location: Hollywood Hills, Ca.
HadYourPhil wrote:
That link does not work...


Hi Phil,

Thanks for pointing that out.
I corrected my URL. It should take you to my site. Scroll down to the "CTC-5" section for pix of 22" Westinghouse color and other mid '50's sets.

-Steve D.

_________________
Check out my vintage color tv site: http://www.wtv-zone.com/Stevetek/


Top
 Profile  
 
 Post subject:
PostPosted: Aug Mon 13, 2007 6:43 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 9509
Location: Chesapeake VA
Nice site Steve, I enjoyed the trip through the early days of color TV... Obvious you are quite proud of your CT100, I would be as well...


The 22" rectangular Westinghouse is interesting... Apparently Motorola wasn't the first to produce such a tube...

Tom


Top
 Profile  
 
 Post subject:
PostPosted: Aug Mon 13, 2007 10:35 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3487
Location: Federalsburg, MD
I have read, in period trade magazines, that there was a real shortage of rectangular tubes for a time in the 60s. In 1960 RCA was really the only one building color tv sets; in 5 years there were maybe 6 or 8, maybe more, plus all the store brands and smaller nameplates who sublet that work out. The industry had been stalled for a number of years as everyone who was ever going to buy a bw tv already had one. When color, at last, finally caught fire everyone wanted a piece of the action. Where RCA began the decade as the only producer of color picture tubes in the world (I presume?) by 1970 there were probably a dozen or more companies cranking them out. Of course, then there came a manufacturing glut and many losers...

Going along with Randy's story of people financing color tv sets, somewhere I have paperwork that came from a local Admiral dealer who used the local bank to finance his customers. It details what everyone owed, who was late on their payments, etc. Kinda interesting.


Top
 Profile  
 
 Post subject:
PostPosted: Dec Thu 09, 2010 4:12 pm 
New Member

Joined: Dec Thu 09, 2010 4:04 pm
Posts: 1
The geometry of the round kinescope resulted in equal expansion of the internal shadow mask and thus more precise control of red screen uniformity. Early rectangular tubes were not stable in terms of their color purity. The RCA CTC-17 receiver was the first model RCA produced with a 25” (actually sold as 225 sq. in. viewing area as I recall due to Federal Trade Commission regulations; it was only about 23” diagonally) rectangular kinescope. By the time the CTC-20 was introduced, they were back to the round kine’s (pronounced Kenny’s) because of the purity issue.

Kind regards to the community.


Top
 Profile  
 
 Post subject:
PostPosted: Dec Fri 10, 2010 12:02 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 369
Even modern rectangular crt's suffer from overheating
shadow masks.We have some Ikegami hi-def CRT monitors
still in use and if you hit those with peak white slightly
above 35 foot lambrets you can see the color purity
change right before your eyes.Punch up black for a couple
of minutes and purity goes back to normal.

Regards,
Swanson


Top
 Profile  
 
Post New Topic Post Reply  [ 37 posts ]  Moderators: Mr. Detrola, 7jp4-guy Go to page 1, 2  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 5 guests



Search for:
Jump to:  



















Privacy Policy :: Powered by phpBB