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
  #1  
Old 02-24-2017, 04:28 PM
benman94's Avatar
benman94 benman94 is offline
Resident Lunatic
 
Join Date: Jun 2011
Location: Detroit, MI
Posts: 1,190
Motorola low level diode color demodulation

The 19 inch Motorolas (chassis TS-902 from 1954) and the earliest 21 inchers they built (chassis TS-905 from late 1956) use a weird double-diode color demodulation scheme that I can't recall seeing in any other schematic. Basically two double diodes are used to demodulate along the -(R-Y) and -(B-Y) axes, and then three triodes are used, one to amplify and invert the -(R-Y) signal, another to amplify and invert the -(B-Y) signal, and a third to amplify G-Y, which is derived from R-Y and B-Y. The difference signals (R-Y, B-Y, and G-Y) are then applied to the appropriate grids of the 19VP22 or 21AXP22, and mixing with the luma (Y) occurs within the CRT itself.

Was this a design that was unique to Motorola? I know difference demodulation became the dominant form of color demod for a while, but did anybody else use the oddball diode circuit?

Last edited by benman94; 02-24-2017 at 05:09 PM.
Reply With Quote
  #2  
Old 02-24-2017, 04:52 PM
Electronic M's Avatar
Electronic M Electronic M is offline
M is for Memory
 
Join Date: Jan 2011
Location: Pewaukee/Delafield Wi
Posts: 14,758
IIRC the GE portacolor used a similar demod circuit.
__________________
Tom C.

Zenith: The quality stays in EVEN after the name falls off!
What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
Reply With Quote
  #3  
Old 02-24-2017, 05:05 PM
benman94's Avatar
benman94 benman94 is offline
Resident Lunatic
 
Join Date: Jun 2011
Location: Detroit, MI
Posts: 1,190
Quote:
Originally Posted by Electronic M View Post
IIRC the GE portacolor used a similar demod circuit.
You're right Tom, the GE Portacolor does use the same basic circuit, only with solid state diodes instead of the vacuum diodes in a 6BV8 or a 6AL5. Thanks.
Reply With Quote
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 06:16 AM.



Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
©Copyright 2012 VideoKarma.org, All rights reserved.