Famicom AV mod - NEW!
UPDATE: I have prepared a better AV mod instructions, for removing the jailbars from video output. Not much changed really, I only added isolation of pin #21 to the old one. JPx72@26.1.2014:
Before you start making this mod, read this topic!
For questions and answers please reffer to this topic on FamicomWorld forum:
For experienced users, here is the needed schematic:
Covered all revisions: HVC-CPU-01 to 08, and HVC-CPU-GPM-02.
For everyone else, here is my NEW solution:NEWS: THIS SOLUTION WORKS BEST ON MODEL HVC-CPU-GPM-02 , OTHER REVISIONS STILL HAVE JAILBARS AFTER THIS, BUT IT'S THE BEST YOU CAN DO! If you want old solution - go HERE
Remove transistor 2SA937 (marked Q1 on board)
Step 2:ISOLATE PIN #21 OF THE PPU!
This guy is showing us where the noise is originating.
Step 3:I recommend building this on the components side (where the chips are) of the main famicom board
Bend pin marked "B" ("base" of the transistor) like shown on the picture
and put it near the PPU with the pins facing up.
Solder pin "B" to pin 21 of the PPU (video).
Next, solder pin "C" ("collector") to pin 20 of the PPU (GND).
Next, solder 150R resistor to pin 22 of the PPU (+5V).
DO NOT remove pins 20 or 22 from the main board, just solder directly to
them. The only pin that needs to be lifted is PIN 21!
You can check some photos of my work here,
(If you accidentaly break one of the "legs"/pins of your transistor Q1 don't worry, you can use any other PNP transistor!)
If you are lost in this step, just follow this schematic:
It is vital to keep all wires as short as possible.
Solder a ceramic capacitor 1uF between pins 20 and 22 of PPU.
Also solder a ceramic capacitor 1uF between pin 40 of the CPU and the near GNDlike you can see on THIS picture.
For even more reducing the bright vertical bars ("jailbars") on screen
STOP- at this point you should have very decent video output, if not, consider next steps -STOP
Step 5:This step is OPTIONAL (although highly recommended by 80sFREAK for reducing the jailbars)
(photo by 80sFREAK)
You can take sound from the "SOU" marked solder-spot on the Rev.01-08, or simply from pin 46 of the cartridge connector (all rev.). You should add a 220uF electrolytic capacitor like this:
Pin 46 of cartridge connector:
I have also prepared for you some pictures of different Famicom board revisions.
I don't have all the pictures, so will be happy if you can add more to my library: