Famicom av mod instructions?

[Samfisher84]

Have tried to find some good guide for it but where?

[NintendoKing]

Code Select Expand

[img]http://www.famicomworld.com/forum/index.php?action=dlattach;topic=4688.0;attach=896;image[/img]

There you go as provided by another member on here, it seems a bit to big though.

Mod edit:
I was told that the original picture here was totally wrong. Use the following site instead:
http://jpx72.detailne.sk/modd_files/fc/avmod.htm

[Samfisher84]

awsome thanks

[NintendoKing]

Remember we are not responsible for your console no longer functioning after the mod; you take full responsibility if it doesnt work.

[FamicomRetroGamer]

Looks risky and if it's done wrongly the console ends up having malfunction which isn't good at all.

Good luck SF84 if you're going to do it.

[ericj]

There's only 4 solder points on the Famicom board itself. It's not really risky at all if you're careful and double-check your work. If it doesn't work right the first time, go back and check your work and make the appropriate fixes. It's a game console, not a pipe bomb. 

[jpx72]

I draw it just to make it look easier. Guess it didn't help  
It's very simple though, You can check the finished PCB on my web site:
http://jpx72.detailne.sk/modd_files/fc/avmod.htm

EDIT: On my webpage is the most recent and most perfectly working schematics provided by a member named kyuusaku. Feel free to try it!

[b1aCkDeA7h]

I draw it just to make it look easier. Guess it didn't help 
It's very simple though, You can check the finished PCB on my web site:
http://jpx72.detailne.sk/modd_files/fc/avmod.htm

That PCB you made is quite nice.

[NintendoKing]

That is really awesome looking, and very professional-like. I would be impressed by such a mod.

[jpx72]

I have done some testing (thanks to marqs from NFGGames.com) and I have changed my schematics to work properly with any famicom (the last one has brightness dropping issues on older PCBs). Also I love his idea of adding the capacitor to PPU - that's a signifficant improvement (reducing the brighter vertical bars)!!!
Check my webpage or look on the attached schematics only.

This schematics is universal (because different Famicom boards have different parts). Isolating the pin 21 of PPU from the PCB isn't necessary.

EDIT: If you experience very bright image, try to experiment with the 2,2k ohm resistor connected to +5V. Try to exchange it with lower ohm resistor, but not lower than 500 ohm!

As I am writing on my webpage, you can use the transistor on your Famicom PCB instead of adding a new one. But to make this schematics universal (and completelly detachable), I am sugesting to build this schematics outside od famicom and connect it directly to pin#21 on PPU.

PS: my old schematics suggested 10uF capacitor between pin21 and transistor. But this only worked on HVC-CPU-GPM-02. So I removed it from this one.

[lillin]

This= awesome
One question though
What other transistors would work with this?

[jpx72]

Any standard transistor, type: PNP, "Bipolar junction transistor (BJT)", hard to say if it's low/medium/high frequency, because there are various definitions, but around 150 MHz it's ok. Original famicom has type 2SA*****, what, according to wikipedia, is "high frequency PNP BJTs". But if you ask in local electronics shop, I'm sure they will help you. Ask for PNP transistor for 5V (and more).

[b1aCkDeA7h]

If I remember right, Radio Shack didn't have it so I just ordered a bag of maybe a hundred of them off of eBay.

[lillin]

Thanks

[kyuusaku]

Also I love his idea of adding the capacitor to PPU - that's a signifficant improvement (reducing the brighter vertical bars)!!!

Empirically the bars are interference from the address bus, you don't need to put a giant-cap on your PPU to lose it.

EDIT: If you experience very bright image, try to experiment with the 2,2k ohm resistor connected to +5V. Try to exchange it with lower ohm resistor, but not lower than 500 ohm!

Any time someone has to experiment in a non-RF circuit there's something wrong. These "AV mods" are common-collector amplifiers so they simply buffer the voltage on the video pin. Your 2.2k /  220 R combo is setting the level too high in parallel with the TV's 75 ohm load. You only need to connect the emitter to the supply though a 300 ohm, and the output cap to the emitter.

I don't know the purpose for the 560p shunt cap, it's creating a low-pass filter with a Fc of 2.58 MHz... Since video is 6 MHz it's doing a bit of harm. I'd think it'd make it blurry...

PS: my old schematics suggested 10uF capacitor between pin21 and transistor. But this only worked on HVC-CPU-GMP-02. So I removed it from this one.

The capacitor is only necessary/only works when using a NPN transistor since the PPU doesn't source current, it sinks it. Using a PNP sources current for the PPU directly.