Playchoice 10 - jailbars

[famiav]

  Hello I'm back on this forum after several years because you may be able to help me 😊 I know this forum talks about the FAMICOM but the Playchoice 10 is similar on many points 😉

I have a Playchoice 10 arcade which works very well which therefore has the famous PPU RGB. The image is very beautiful except... jailbars!

I had succeeded thanks to this forum to eradicate jailbars on my Famicom but since it'is a different PPU on PC10, I wanted to know if you would have a solution to my problem...

Thank you very much in advance for your answers!

(PS : I'm french, I use Google Translate...)

[famiac]

It's not possible to eliminate them completely, but this page shows the best way to reduce their intensity:
http://vaot.mydns.jp/fc/rwfcrgb.htm

one thing that hasn't been attempted is putting series resistors on the address/data lines going to the PPU. I plan to try it... someday.

[Stephen]

Yea, I would recommend 100Ω inline resistors on the data lines first; probably less intrusive as a first try. That being said, I have not worked on RGB PPUs before.

[famiac]

I wouldn't recommend yet, as the idea hasn't been tested. The person testing it stands to do a lot of work for little payoff.

[famiav]

thank you for your first answers.  actually, I'm afraid of killing the PPU by trying changes that haven't been approved.  the only thing I did was ground the PC10 PPU with copper tape, but that didn't change anything. 

@famiac, I'll try the first step of your first link in Japanese and see what happens... I have two PC10 motherboards (one with a PPU, the other way), I can put the PPU on both  cards.  I can use a card for testing as long as it doesn't damage the only PPU I have!

 
@Famiac, do you think I can experiment with one of my PCBs without damaging the PPU?

[famiac]

there are really only two steps that substantially reduced the jailbars on my 2C03B-modded famicom. They should apply to your playchoice PCB as well.

1- connecting a 4.7uF capacitor between the "notch" at the top of the PPU and the +5V supply pin


2- separating the RGB output pins from the PCB and amplifying the signal as close to the PPU as possible


Either the THS7314 or the THS7316 will work fine as an amp. You can use an "SOIC-8 to DIP-8" adapter board like this one to make soldering easier.


The most "risky" part is cutting the RGB traces going to the PPU on your playchoice PCB. Routing the output might also be tricky... I wrote some instructions that should make it clearer.

Amp install instructions:

If you have a dual monitor system, you need to disconnect pins 1,2 ; 3,4 ; 10,11 of the CD4066 chip (marked 2E) from the PCB.
Connect the output of your RGB amp to pins 1, 4, and 11 of the CD4066
then, you can connect pins 2, 3, and 10 to pins 1, A, and 2 of the edge connector. Those pins correspond to Red, Green, and Blue.
Finally, you need to remove R47, R57, and R67.

If you have a single-monitor Playchoice 10 PCB, then you can connect the output of your amp directly to the edge connector.
Red-Green-Blue should correspond to pins 9, 10, and 12.
You also need to remove transistors Q13, Q16, and Q19.

hopefully this makes the steps clear.