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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions. |
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25th Aug 2006, 6:14 pm | #1 |
Retired Dormant Member
Join Date: Jul 2005
Location: West Yorkshire, UK.
Posts: 1,700
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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 ___/\ /\ ___| \/ \/ 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 Last edited by Kat Manton; 25th Aug 2006 at 6:23 pm. Reason: Added note about modeline |
25th Aug 2006, 6:28 pm | #2 |
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Join Date: Mar 2003
Location: Bishop's Waltham, Hants, UK.
Posts: 939
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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. |
25th Aug 2006, 6:32 pm | #3 |
Retired Dormant Member
Join Date: Jul 2005
Location: West Yorkshire, UK.
Posts: 1,700
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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 |
30th Aug 2006, 8:10 am | #4 | |
Retired Dormant Member
Join Date: Dec 2003
Location: Solingen, Germany
Posts: 727
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Re: FothTV (405-line from a PC) - KISS Circuit
Quote:
Place a 180R at red , 680R at blue and 47R at green. Connect them at the 47uF. Darius |
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