NESRGB4 Support

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owen2a03
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Joined: Fri Sep 30, 2022 1:19 am

NESRGB4 Support

Post by owen2a03 »

I've seen several questions about issues with it here so I figured I'd ask here.

I had recently installed the NESRGB in my AV Famicom, but I've noticed a rise in issues with select games that utilize the technique of differently-colored horizontal tiles.
I went over my solder points (that I can access with everything assembled) but I saw no changes.
My capture devices are packed away now but I took some pictures to try to show this with the hopes that anyone may know what this issue may be coming from...

https://i.imgur.com/YMZJelw.jpeg
GI Joe was the first game I played and noticed. There is now darker coloration under the white bars which are meant to be darker red-brown

https://i.imgur.com/KvhD72p.jpeg
Noah's Ark gets yellow coloration at the top of the gray-ed palette for the water

https://i.imgur.com/4ctg8ov.jpeg
Rampart is the worst of all. It gets a really bad white discoloration at the top of the scroll and freaks out the bottom of the scroll when in motion

I am using composite for the time being as I wait for SNES HDRV cables to come in stock, but the s-video on my retrotink shows the same issues as my TV.

I've become very concerned about this, and if the PPU might've even gotten fried... Any help or ideas would be greatly appreciated!!
Last edited by owen2a03 on Tue Oct 11, 2022 2:40 pm, edited 1 time in total.
viletim
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Location: Sydney, Australia
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Re: Color/scrolling effects issue with NESRGB!

Post by viletim »

owen2a03,

You've found a bug in the NESRGB version 4. I can reproduce the bug and can confirm that the RGB attenuator is indeed broken. I made a mistake in the code, so it it gives the signal a boost instead of attenuating it. You see yellow water Noah's Ark because the red and green channels are being boosted.

The only solution I have is to disable the attenuator in hardware. It's not ideal, but better that the current behavior. You can disable the RGB attenuator by (very carefully) removing three surface mount resistors on the NESRGB board.

Image
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owen2a03
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Re: Color/scrolling effects issue with NESRGB!

Post by owen2a03 »

Thank you for the reply Tim!

I've removed them and it's working out much better now.
Image

I was panicking and fearing I might've done something horribly wrong! the assistance is big load off my mind. Hopefully there'll be a better fix for it... but I am satisfied.
Thank you again for the quick reply!
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Josh128
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Re: Color/scrolling effects issue with NESRGB!

Post by Josh128 »

Fantastic! Thanks for this Tim!

I have another question for you-- recently, my NESRGB seems to "almost" lose sync on mostly dark scenes, such as title screen on Zelda 2, certain password screens, etc. Its like the top of the screen wants to "warp" a bit, but quickly returns to normal when getting more color population on the screen. Almost like the sync is about to let go.

I have no idea whether this is specific to my TV, a 36" Trinitron Wega, my NESRGB unit, or my NES itself (perhaps drying caps?). All I know is that no other system has this issue on this TV, so Im assuming the TV is not the issue.
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owen2a03
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Re: NESRGB4 Support

Post by owen2a03 »

Not to detracted from Josh's post, but now another (this time self inflicting..) issue arose for me.

I had soldered up the connections for the controller port to the palette selection pads on the rgb board, and at some point it seems the wires to the pads must have shorted with components on the famicom board (namely, the long pins of the transistor Q3 next to the crystal) where they ran across..
After powering on, all of the eight LEDs go on with very dim lights, even after desoldering the wires entirely, and carts do not boot.
I imagine I've fried something on the board.. and I hope I can get some confirmation of what I've done, even if it means the rgb board is toast..

I've reinserted the ppu to the socket on the main board and soldered back the original video and it does work, so there's definitely nothing wrong with the system.

Thank you for any suggestions or confirmation..
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