What's currently the best AV mod for the Famicom?

Hmmm, it sounds like simply lifting pin 21 away from the board solves the problem, you don't even need to add any extra components.

 

Just finished my mod!

Confirming that a 100uf capacitor between pins 20 and 22 was yet another phenomenal jailbar decrease. Looks perfect to me now.

My Recipe:
- GPM-02 model
- Built on separate circuit board
- Kyuusaku schematic (on Page 1)
- Pin 21 isolated (lifted)
- 100uf capacitor between PPU pins 20 and 22
- Mono audio from pin 46, run through 220uf capacitor (this may be sub-optimal...but it seems to work fine)


See full-res here:
http://i.imgur.com/znZ4jZC.jpg

Might not be the prettiest (or most competent), but for a "learn how to electronic" project, I'm pretty happy with it

 

It's the biggest change, but a capacitor between pins 20 and 22 gets you the rest of the way there. Maybe 70% Pin 21, 30% Pins 20/22.
I tried a 1uf cap at first, but it didn't seem to make a difference. A 100uf cap was night and day as soon as I touched its contacts to the board.

 

Also, Fireaza, I used a TRRS connector as well, but I couldn't put it on the back panel of a GPM-02 model without major surgery.
So...I placed the connector internally, and strung the video cables out the Player 2 cord hole (forgoing the grommet).

 

Looks good:encouragement:

 

Eh, I've already got some 100uF caps ordered, so I might as well install one

Really? Pikkon seemed to have no trouble installing one in his, did you use a 3.5mm jack or something bigger?

 

Does your fami look like this.
http://jpx72.detailne.sk/collection_files/consoles_files/nintendo/famicom1/pcb_front_full_2.jpg

If so that's why you couldn't get the trrs jack in there.

 

Damn! That's what mine looks like!

 

Yep, GPM-02. The RCA-style RF jack is actually "molded" as part of the shielding, rather than mounted on the PCB.

 

I noticed that, I figured it could be de-soldered or cut away from the shield.

 

You're welcome to try
I got lazy and have other projects to work on

 

Alright, all the components have arrived! Just a few remaining questions:
1) Should the transistor be removed from the board as the diagram Pikkon posted seems to imply, or should it be removed, and re-soldered on the other side of the board like in the tutorial Mangaman posted? Or maybe that diagram is implying that the transistor should be left where it is and you solder the wires to it's solder points, I'm not sure.
2) Would it be a good idea to stick a 1uF cap on the audio as was suggested in my PC Engine thread?
3) For the ground and 5v, I'm thinking I'll get those from the cartridge connector. Here's a diagram I found:

So, this means that ground is on pin 01 and 5v is on pin 31 correct?

 

Okay, I've done the mod, but it's not working. I get audio (though with a lot of static) but the picture is nothing but rolling static. I'm not sure if I haven't installed the components properly, or if there's something else. Here's some photos of the soldering:


As you can see, I used Kynar wire, might this not be up to the job? In case it comes up, for pin 21, what I did was disconnect the leg from the board, ran a short wire from the leg on one side of the board around to the E leg of the 2SA937 transistor on the other side of the board. Not sure it it means anything, but I'm not getting any continuity on the 220uF capacitor, while I am on the 100uF one. Strange thing is, even unused 220uFs have the same behavior.

 

Pin 21 of the ppu should connect to the base of the pnp transistor.

This pic should help.

 

Yep, that's what I've done (pin 21 goes to leg B correct? At least, according to the diagram on page 1), here's clarification:

Red circles are the three legs of the transistor. I might have it backwards though, the leg under the notch is leg E correct?

 

Did you follow this for the transistor.

http://jpx72.detailne.sk/modd_files/fc/avmod.htm

 

No, I was hoping I could get away with leaving the transistor where it is and not risk snapping off the leg you need to bend. Is that not possible? I'll try their instructions and see if anything changes!

*EDIT* I realized I'd forgotten to include the capacitor on the audio line, which would probably be part of the reason for my noisy audio. So I soldered it on just now. Went to test if this improved the audio, and not only is the audio fine now, but the picture is too! Putting the metal shielding in place must have been the cause, since I didn't have it installed before. Who knew it was so important?

*EDIT* Or maybe it's not. Wiggling the plug seem to makes the video alternate between working and not, seems like the jack is touching something.

 

Put some electrical tape under the jack so it doesn't interfere with anything.

 

The weird thing is, it seems to work when the jack is angled downwards (i.e when it's far more likely to be touching something). Either way, I think I have narrowed the source of the problem down to the cable, as when I plug my headphones in, I get clear audio, no matter how much I jiggle the plug around. If I fiddle with the cable, I can get it to work, but it seems like replacing it will be the solution. Thanks for trying though!

Anyway, I've noticed I'm still getting faint jail-bars in the video, I've lifted pin 21, put the 100uF cap across those 2 pins, what more can I do? Put some copper tape under the PPU? Or does unshielded Kynar wire simply not cut it?

 

Well you could remove the some of the resisters and coils,that's what I did to mine then added some electrical tape under the jack so it would not be touching anything.

As for the jail bars what kind of tv are you using.