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 Post subject: nes rgb mod shaky video
PostPosted: Fri Dec 25, 2020 9:55 pm 



Joined: 22 Dec 2020
Posts: 2
Hello i own an ikegami TM20-80R rgb monitor

I recently bought a rgb modded nes off ebay.

And just recently got around to testing it.

So i have a video problem. Im using two scart cables one plugged into the nes and one plugged via bnc into the back of my ikegami monitor.

I have a problem where the video becomes unstable and shakes or shifts back and forth.

I just wondered if anyone had any ideas what could cause this? Could it be my rgb cable?

I dont think it is the monitor as it works with a different rgb cable hooked up to a sega genesis.

Any help would be appreciated.


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 Post subject: Re: nes rgb mod shaky video
PostPosted: Mon Jan 11, 2021 8:49 pm 


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Joined: 21 Jun 2019
Posts: 73
Location: Atlanta, GA
I don't use modded consoles but for lack of responses, I'll weigh in. First, bad RGB mods are eBay stuff of legend. Would help if you can try the NES on another RGB monitor, or open up the console and take pictures of the mod to confirm it was done correctly. I would not be able to judge.

Second, if you have the Tim W. NESRGB kit installed, this is a known and solvable issue due to off-spec NES sync timings: https://etim.net.au/nesrgb/background_fault/de-jitter.html
Site links this video with jittering example. I assume it matches what you see: https://www.youtube.com/watch?v=EEt7XFfreQM

Mentions you may need an Altera USB Blaster clone programmer, with emphasis on clone, since the real thing costs $300. I found an old thread that deals with real and fake clones and so forth:
https://www.eevblog.com/forum/fpga/altera-usb-programmer/?PHPSESSID=lljetb101ohqel34mju8hbnnn3

What I'd like is someone more knowledgeable to comment on this:
Quote:
Version 2.3 - 4/3/2020 - Removed the de-jitter feature entirely. This is an experimental firmware, not loaded on production boards.


Does the latest NESRGB kit have no solution to jittering then? Just means you need an RGB monitor more accepting of off-spec video signals?

While much less likely the issue, I get jittering on my PS2 when the Multi Out connector is loose. May as well take 10 seconds to see that everything is connected securely and RGBS cables plug into the correct RGBS BNCs. The plating on the NES RGBS connectors could be damaged but also very unlikely. I've used a bad JP21 cable that put horizontal bars on the picture or darkened the screen, but can expect capacitors to fail on a 25 year old cable. I wouldn't expect the cable itself to cause jittering, which would be to say it's messing the sync signal up.


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