Hi there,

first, sorry I'm not writing in Polish, but as many of you know, my Polish is piece of shit :)

I have a problem. I made an UltraVideo mod (which is enhanced SuperVideo mod).
http://www.atari8.co.uk/downloads/Ultra … %201.0.pdf

Well, the picture works. But the colour is very noisy, it looks like on untuned old TV.
The S-Video cable is OK, my monitor (LG M1721A) is also OK (works fine with C64 connected trough S-Video).
What I found is there is difference between Ultra- and SuperVideo modifications.
On UltraVideo, the resistor R205 has to be replaced by a diode. On SuperVideo, there should be 75ohm resistor.

But. When I unsolder it (leave the space blank without diode/resistor), the picture goes B/W and is perfectly clean.
When I put here the diode (Ultra), it becomes colourful and awfuly noisy. When there is a resistor (Super) instead of diode, there is a little bit less noise, but still, awful picture.

See the pics.

Again, I did everything from the PDF. Removed modulator, changed resistors, diode, capacitator, checked everything, there is no cold-connection. Cable is OK, connector too. I don't know and this is my last chance.

The computer is 800XE with 320kB and QMEG.

Thank you very much.

Factor6

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2

in my case shorting one of pins (or rather pads) to ground of unsoldered modulator helps to cure the issue
seems like reference level for chrominance is missing, and causing this phenomena

przechodze na tumiwisizm

3 Ostatnio edytowany przez drygol (2013-01-03 14:48:46)

Mam podobny problem , jak tylko dokladam chrominancje to obraz sie strasznie kaszani.
Candle , pamietasz moze ktory pad groundowales i czy bylo to robione dioda czy moze zwykla zwora ?

EDIT: Ok ogarnelem ;)