Videokarma.org TV - Video - Vintage Television & Radio Forums

Videokarma.org TV - Video - Vintage Television & Radio Forums (http://www.videokarma.org/index.php)
-   Early Color Television (http://www.videokarma.org/forumdisplay.php?f=36)
-   -   Motorola low level diode color demodulation (http://www.videokarma.org/showthread.php?t=268589)

benman94 02-24-2017 04:28 PM

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?

Electronic M 02-24-2017 04:52 PM

IIRC the GE portacolor used a similar demod circuit.

benman94 02-24-2017 05:05 PM

Quote:

Originally Posted by Electronic M (Post 3179333)
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.


All times are GMT -5. The time now is 05:49 AM.

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