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PostPosted: Sat Feb 17, 2018 12:37 pm 
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Hi, all! Long-time lurker, first-time poster here. I wasn't sure if this needed to go in here or the Newbie Help forum, so I apologize if it's in the wrong place. I also checked about three years' worth of old posts with no results, so here I am! :beer:

I recently took the plunge and went all-in on RGB. SNES and Genesis are sexy in RGB, and I purchased an AV Famicom to mod. Aside from an issue desoldering the PPU (which I replaced with an intact one from a broken NES at the store I work at) and a few traces on the Fami board that a friend had to repair because I got a bit happy with my desoldering iron, I had no issues installing the mod, or so I thought.

Basically, I can't get any kind of RGB output with a known-working SCART cable. My OSSC just does not see a signal from the thing, so I'm in need of some help.

If I try to run it over a SNES composite cable with the board installed I get a picture that looks like the normal game but it's white. Not a brightness-level white, like a monochrome white with no black in the picture. Unfortunately I'm not in a place where I can take a picture of how it looks, but If I take the PPU out of the RGB board and put it back into the Fami board it works just fine over composite.

-- Jumper J8 is open because I'd like to use TTL cables instead of 75ohm (so I can use the same cables as my 2-chip SNES)
-- J3 and J5 are properly shorted for Power and NTSC.
-- I'm using CS# as my video out, because again I'd like to use the same cables as my SNES. I did try outputting through V with no luck.
-- 3 and GND are jumped because I'd like to use the default palette.
-- I didn't cut the video trace on the bottom so I could switch between RGB and Composite as needed.
-- I did already check the voltage regulator just in case I had one of the faulty ones, it's fine.
-- I used a multimeter to check continuity of the ppu to the output pins, they checked out fine. Same with the wires from the rgb board to the video out pins on the Fami board.

Here are pictures of the board and my wiring.

Thanks to all who took time to read this. Help is much appreciated! :D


Last edited by DaRabidDuckie on Sat Feb 24, 2018 6:20 pm, edited 1 time in total.

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PostPosted: Sat Feb 17, 2018 12:53 pm 
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DaRabidDuckie wrote:
If I try to run it over a SNES composite cable with the board installed I get a picture that looks like the normal game but it's white. Not a brightness-level white, like a monochrome white with no black in the picture. Unfortunately I'm not in a place where I can take a picture of how it looks, but If I take the PPU out of the RGB board and put it back into the Fami board it works just fine over composite
That's consistent with how the RGBNES works: it replaces the PPU's composite video output with a signal to distinguish between sprites and background.

I'm not certain about anything else, unfortunately.


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PostPosted: Sat Feb 17, 2018 8:16 pm 
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lidnariq wrote:
That's consistent with how the RGBNES works: it replaces the PPU's composite video output with a signal to distinguish between sprites and background.


Well, that actually does gives me some hope that something in this is working, thanks! ^_^


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PostPosted: Sat Feb 17, 2018 8:50 pm 
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Quick questions:

* Is it really always solid white? Is there ever any sound? If there is sound, do black sprites never appear?
* Are the revisions of the CPU and PPU the same? I see you now have a 2C02G PPU; is it a 2A03G CPU? (2A03E or 2A03H probably ok, not certain; 2A03letterless probably a problem)
* Do you have an oscilloscope? Voltmeter?


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PostPosted: Sat Feb 17, 2018 9:00 pm 
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lidnariq wrote:
Quick questions:

* Is it really always solid white? Is there ever any sound? If there is sound, do black sprites never appear?
* Are the revisions of the CPU and PPU the same? I see you now have a 2C02G PPU; is it a 2A03G CPU? (2A03E or 2A03H probably ok, not certain; 2A03letterless probably a problem)
* Do you have an oscilloscope? Voltmeter?

Thanks for the reply!

* There was sound, yes. I didn't actually try playing the game when I was last testing at the shop, though. I just saw a very white version the title screen of Mega Man 3, heard music, and turned it off. I can check further Monday the next time I'm at work.
* The CPU is 2A03H.
* I don't have an oscilloscope, but I do have a voltmeter. I'm used to checking continuity and basic voltage readings (I work on arcade sticks and USB devices a lot) but I don't know much about it past that.


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PostPosted: Sat Feb 24, 2018 6:19 pm 
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Finally got it all figured out. Someone at the shmups forums directed me to a post from Tim Worthington where he mentioned that all pins from the PPU in the NESRGB go straight through the adapter board to the Famicom board except for 2-9 and 14-17. Using that I figured out that pin 37 had a loose connection. I resoldered it and took care of that issue.

I'd also had the board incorrectly wired to the nintendo AV port. I wanted to set the board to output TTL and I mistakenly connected CS# to pin 9 (composite) instead of Pin 3 (CSYNC) on the AV port.

After resolving those two issues, the thing works beautifully!

Image


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