NES loss of RF video

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Lee1978
Posts: 5
Joined: Mon Oct 12, 2020 4:44 am

NES loss of RF video

Post by Lee1978 » Tue Mar 02, 2021 10:51 am

Hi all, my issue is with a PAL NES and as per the title I’ve lost RF video, the sound still works and both video and sound work on the composite output. Does anyone have a circuit diagram or any pointers that might help at all?

lidnariq
Posts: 10457
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: NES loss of RF video

Post by lidnariq » Tue Mar 02, 2021 12:03 pm

We don't have a reverse-engineered PAL RF modulator, but we have a reverse-engineered NTSC one:
https://console5.com/wiki/File:NES-001- ... Switch.png
and we have the reverse-engineered French AV box (which is baseband only):
viewtopic.php?t=18861

You should be able to use those as a proxy for for what to expect. These RF modulators usually seem to FM-modulate the audio first onto baseband video, and then AM-modulate both together to the final broadcast band, so there is probably not much hardware between the baseband video buffer and the place where the audio is mixed in. So you shouldn't have to test many parts.

Lee1978
Posts: 5
Joined: Mon Oct 12, 2020 4:44 am

Re: NES loss of RF video

Post by Lee1978 » Tue Mar 02, 2021 12:22 pm

Thanks for the response and for the link. It's got really odd now though, the console has become picky about the games it likes. Previously when i said i'm able to play games through composite but could only get audio through RF, well the console no longer plays those games, now i have just a few games that work, these ones play perfectly on composite and will work correctly on RF if i turn the tuning pot full clockwise until i get a crappy picture then dial it back.
All this started when i tried making a cart with a new type of memory chip to what i typically use, with a different pin-out, its possible i connected it up wrong i suppose, could a badly wired chip cause a console to fail in this manor?

lidnariq
Posts: 10457
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: NES loss of RF video

Post by lidnariq » Tue Mar 02, 2021 1:49 pm

Depends on what's on the new board, but it's possible.

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