Videokarma.org

Go Back   Videokarma.org TV - Video - Vintage Television & Radio Forums > Early Color Television

We appreciate your help

in keeping this site going.
Reply
 
Thread Tools Display Modes
  #136  
Old 06-21-2011, 06:44 PM
Pete Deksnis's Avatar
Pete Deksnis Pete Deksnis is offline
15GP22 demo @ ETF 2007
 
Join Date: Jan 2005
Location: Big Rapids, MI
Posts: 738
Quote:
Originally Posted by miniman82 View Post
So earlier on they were using different basing if I understand this right, which would place my tube later on in the development timeline and peg tubes with different pin counts as earlier ones?
Something like that. I liken these exercises to riding an old mountain railroad for the first time: plenty of hidden curves ahead; somebody was there before us to build the thing, but it's all new now...

Pete
Reply With Quote
  #137  
Old 06-21-2011, 08:38 PM
John Folsom's Avatar
John Folsom John Folsom is offline
VideoKarma Member
 
Join Date: May 2004
Location: Melbourne Florida
Posts: 938
Nick, The earlier tubes had a 14 pin stem and base. I would speculate that this was because they had a 14 pin stem and base in the inventory. Later on, it became obvious that additional electrical isolation was needed between the convergence pin at [edit] 7-9KV and the other pins, so a 20 pin stem and base were developed, allowing 3 blank pin locations on either side of the convergence electorde.

I just checked my Sparton metal bell CRT, and it is a 20 pin 6 bolt CRT just like yours, with a type number of C73547, just like yours. My bell rim number is D255, and I believe Pete said you rim number is D205 (?). This all seems to make sense. My Sparton set is a early 1953 NTSC set, as best I can tell.
__________________
John Folsom

Last edited by John Folsom; 06-22-2011 at 11:03 AM.
Reply With Quote
  #138  
Old 06-21-2011, 09:14 PM
miniman82's Avatar
miniman82 miniman82 is offline
First Light: 1952-2011
 
Join Date: Jun 2009
Location: Great Mills, MD
Posts: 4,073
Update: took the tube out of the box, and it's definitely D225. Only 30 made between ours, if the assumtion of a production serial code is correct.

Attached Images
File Type: jpg IMGP4671.jpg (46.0 KB, 204 views)
__________________
Evolution...
Reply With Quote
  #139  
Old 06-21-2011, 09:25 PM
John Folsom's Avatar
John Folsom John Folsom is offline
VideoKarma Member
 
Join Date: May 2004
Location: Melbourne Florida
Posts: 938
Thanks, Nick. Well it is all very interesting.
__________________
John Folsom
Reply With Quote
  #140  
Old 06-21-2011, 10:00 PM
miniman82's Avatar
miniman82 miniman82 is offline
First Light: 1952-2011
 
Join Date: Jun 2009
Location: Great Mills, MD
Posts: 4,073
Quote:
Originally Posted by John Folsom View Post
Later on, it became obvious that additional electrical isolation was needed between the convergence pin at 3-4KV and the other pins, so a 20 pin stem and base were developed, allowing 3 blank pin locations on either side of the convergence electorde.
Makes perfect sense.

Hey, speaking of convergence...

This thing has a long string of megohm resistors coming off the HV rectifier, with the convergence pot right in the middle and more resistors after it. It looks electrically just like the way it was done on the CT-100, except by that time they actually had a 50meg resistor to use in the circuit. What do your proto sets have for convergence?
__________________
Evolution...
Reply With Quote
Audiokarma
  #141  
Old 06-21-2011, 10:48 PM
Steve McVoy's Avatar
Steve McVoy Steve McVoy is offline
VideoKarma Member
 
Join Date: Oct 2002
Location: Columbus, Ohio
Posts: 1,128
Your set doesn't appear to have a convergence transformer like the CT-100, so the question becomes how did they accomplish dynamic convergence, or maybe the question is "did they use dynamic convergence". I would be curious to know if there are other connections (capacitors to be specific) to the convergence grid of the CRT?
Reply With Quote
  #142  
Old 06-21-2011, 11:32 PM
John Folsom's Avatar
John Folsom John Folsom is offline
VideoKarma Member
 
Join Date: May 2004
Location: Melbourne Florida
Posts: 938
Nick, Here is a photo of the bottom side of he CBS prototype. It appears to use large high-voltage resistors, but it has been many years since I was under the chassis, so the details are vague. I have never had the HV cage cover off the Sparton, but as it appears to be a close cousin to the production Sparton set shown in Sames, I expect it will also have 50 megohm (or similar) high voltage resistors. Both of these sets are, shall we say, more mature than your set. :-)
Attached Images
File Type: jpg RX89_BACK_BIG.jpg (146.8 KB, 125 views)
__________________
John Folsom
Reply With Quote
  #143  
Old 06-21-2011, 11:48 PM
Penthode's Avatar
Penthode Penthode is offline
VideoKarma Member
 
Join Date: Jun 2009
Location: Syracuse, NY
Posts: 659
If this prototype dates from 1950-51, how far along was it's development?

Has anyone identified whether this is a set still running on the dot sequential principle or whether the design had progressed to the constant luminance principle with interleaved chroma?

Is there any schematic information with this set? It would be very interesting to reverse engineer this set to find out what the design comprises of.

Note: seems I missed an earlier part of this thread. I see from Ed's post that progress had moved to CPA and possibly later to the early '53 NTSC development closer to the final standard.

It will be interesting to see what the reverse engineering reveals.

Last edited by Penthode; 06-21-2011 at 11:58 PM.
Reply With Quote
  #144  
Old 06-22-2011, 10:57 AM
miniman82's Avatar
miniman82 miniman82 is offline
First Light: 1952-2011
 
Join Date: Jun 2009
Location: Great Mills, MD
Posts: 4,073
Quote:
Originally Posted by Steve McVoy View Post
Your set doesn't appear to have a convergence transformer like the CT-100, so the question becomes how did they accomplish dynamic convergence, or maybe the question is "did they use dynamic convergence". I would be curious to know if there are other connections (capacitors to be specific) to the convergence grid of the CRT?

That's exactly what I'm wondering. The other end of the resistor string has a wire that goes under the chassis, with connections to many different parts. So perhaps it does have dynamic, but it's done in a different way?


Thanks for the picture, John. I can see the 50meg resistors on that set, so you're right- it is more 'advanced' than mine.
__________________
Evolution...
Reply With Quote
  #145  
Old 06-22-2011, 12:00 PM
John Folsom's Avatar
John Folsom John Folsom is offline
VideoKarma Member
 
Join Date: May 2004
Location: Melbourne Florida
Posts: 938
Nick, Attached is a scan of the schematic from the June 1951 RCA symposium on tricolor picture tube development. While this features a RF HV supply and differs considerably from your sets configuration, it does show both vertical and horizontal dynamic convergence transformers. It would seem quite odd if your set did not incorporate some type of dynamic convergence.
Attached Images
File Type: jpg RCA PROTO JUNE 1951.jpg (112.7 KB, 83 views)
__________________
John Folsom
Reply With Quote
Audiokarma
  #146  
Old 06-22-2011, 12:53 PM
Steve McVoy's Avatar
Steve McVoy Steve McVoy is offline
VideoKarma Member
 
Join Date: Oct 2002
Location: Columbus, Ohio
Posts: 1,128
Nick, if you follow the wiper of the convergence pot, where does it go? This is where the convergence stuff would be.
Reply With Quote
  #147  
Old 06-22-2011, 03:26 PM
miniman82's Avatar
miniman82 miniman82 is offline
First Light: 1952-2011
 
Join Date: Jun 2009
Location: Great Mills, MD
Posts: 4,073
Quote:
Originally Posted by Steve McVoy View Post
Nick, if you follow the wiper of the convergence pot, where does it go? This is where the convergence stuff would be.
To the CRT, nowhere else.
__________________
Evolution...
Reply With Quote
  #148  
Old 06-22-2011, 03:29 PM
Steve McVoy's Avatar
Steve McVoy Steve McVoy is offline
VideoKarma Member
 
Join Date: Oct 2002
Location: Columbus, Ohio
Posts: 1,128
I think that means that the set has no dynamic convergence, which is strange. But a full schematic will tell for sure.
If you look at the schematic that John posted you'll see a 10kv capacitor from the convergence pot to the circuitry that provides the waveforms for convergence.
Reply With Quote
  #149  
Old 06-22-2011, 03:35 PM
miniman82's Avatar
miniman82 miniman82 is offline
First Light: 1952-2011
 
Join Date: Jun 2009
Location: Great Mills, MD
Posts: 4,073
There is a doorknob cap mounted under the chassis, but I have no idea what it's connected to.
__________________
Evolution...
Reply With Quote
  #150  
Old 06-22-2011, 07:04 PM
Dave A's Avatar
Dave A Dave A is offline
VideoKarma Member
 
Join Date: Aug 2003
Location: SE Pennsylvania
Posts: 1,225
For John's request and for comparison, my 6-bolt, 14 pin prototype tube is paper tagged;

Developmental type - C73293C
Serial - L3046R

Rim stamped - D229

And it has acquired a swooping crack right across the faceplate but not edge to edge. No idea how that happened. Have not looked at it in 5 years. Gotta be careful now.
__________________
“Once you eliminate the impossible...whatever remains, no matter how improbable, must be the truth." Sherlock Holmes.
Reply With Quote
Audiokarma
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 09:19 PM.



Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
©Copyright 2012 VideoKarma.org, All rights reserved.