UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Television Standards Converters, Modulators etc

Notices

Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

Closed Thread
 
Thread Tools
Old 25th Aug 2006, 5:14 pm   #1
Kat Manton
Octode
 
Kat Manton's Avatar
 
Join Date: Jul 2005
Location: West Yorkshire, UK.
Posts: 1,710
Default FothTV (405-line from a PC) - KISS Circuit

Hi,

I've been pondering the complexity of the MkII RGB combiner, trying to come up with something simpler and consequently easier and quicker to lash up.

This is the end result, it uses the smallest number of parts I think it's possible to get away with while still "working".

This just crudely adds composite sync to the green video signal, ignoring red and blue. I've tried it with monochrome and colour DVDs and it works pretty well, considering. Field-sync is just one broad pulse which my fussy Pye monitor doesn't like, I get line-pairing as happens with the XORed syncs from the "MkII". But I do get a locked 405-line picture. Well, sort of...

I'm not sure what a VHF modulator will make of it, though; I've still not built one.

But, here it is - it could be worth trying this first, then work up to better circuits later

Code:
         | | 47uF
GREEN ___| |_________________________
         | |                         |
       - | | +                       |
                             680R    |
HSYNC ___________       ___/\  /\  __O___ GREEN + CSYNC
                 \    _/     \/  \/
                  \   /|
                  =====  
                    | 2N3904
           1k0      |
VSYNC ___/\  /\  ___|
           \/  \/
(I'm not claiming originality; I found a few circuits for feeding "Sync on Green" monitors while trawling the 'net for ideas, this is a rip-off of one of them...)

So... you need this, a suitable PC and a modulator...

I should add that this requires both syncs to be negative-going, so you need "-hsync -vsync" in the modeline.

Regards, Kat
__________________
Voider of Warranties.

Last edited by Kat Manton; 25th Aug 2006 at 5:23 pm. Reason: Added note about modeline
Kat Manton is offline  
Old 25th Aug 2006, 5:28 pm   #2
jim_beacon
Heptode
 
jim_beacon's Avatar
 
Join Date: Mar 2003
Location: Bishop's Waltham, Hants, UK.
Posts: 939
Default Re: FothTV (405-line from a PC) - KISS Circuit

Hi Kat,

I've been toying with this kind of idea for a while (also prompted by a web search). Is there any reason why the RGB signals can't be mixed with resistors? It would then at least approximate a monchrome signal (OK, so it may up the parts count by 6).

Jim.
__________________
Jim Beacon G1JBG
www.g1jbg.co.uk
jim_beacon is offline  
Old 25th Aug 2006, 5:32 pm   #3
Kat Manton
Octode
 
Kat Manton's Avatar
 
Join Date: Jul 2005
Location: West Yorkshire, UK.
Posts: 1,710
Default Re: FothTV (405-line from a PC) - KISS Circuit

Hi Jim,

Nope, no reason at all; now I've proven this one works; guess what I'm lashing up right this minute?

Regards, Kat
__________________
Voider of Warranties.
Kat Manton is offline  
Old 30th Aug 2006, 7:10 am   #4
oldeurope
Heptode
 
oldeurope's Avatar
 
Join Date: Dec 2003
Location: Solingen, Germany
Posts: 727
Default Re: FothTV (405-line from a PC) - KISS Circuit

Quote:
Originally Posted by jim_beacon View Post
Hi Kat,

I've been toying with this kind of idea for a while (also prompted by a web search). Is there any reason why the RGB signals can't be mixed with resistors? It would then at least approximate a monchrome signal (OK, so it may up the parts count by 6).

Jim.
Hi Jim, you need only three additional resistors.
Place a 180R at red , 680R at blue and 47R at green.
Connect them at the 47uF.

Darius
__________________
RADIO & TV SERVICE

oldeurope's blogs
oldeurope is offline  
Closed Thread

Thread Tools



All times are GMT. The time now is 7:56 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at http://www.vintage-radio.net.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright ©2002 - 2017, Paul Stenning.