AV mod made "easy"? - updated, more questions

Started by SlumberingWeird, June 05, 2020, 10:26:40 am

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SlumberingWeird

June 05, 2020, 10:26:40 am Last Edit: June 12, 2020, 04:03:28 am by SlumberingWeird
Hello!

I recently stumbled upon this mod on YouTube:
https://youtu.be/ky8rFPbzGMU

It seems pretty good! I was looking into it, I have a console coming from Japan, I own a soldering kit, and I can easily get the parts; but I have a fair few questions regarding the build, so I'll start at the beginning and hope someone can answer them.

1) If I were to solder AV cables directly to the board/resistor/capacitor, would I need to ground a third cable, or simply keep the audio and video with only one audio channel? It looks to me like the only thing being grounded is the jack, as the second audio channel is a duplicate as opposed to actual surround. I don't mind the cables being permanent as the controllers already are, and would rather bypass the jack as it feels like an unnecessary extra component.

2) Does the wattage of the resistor matter at all? The highest one I can find is either 3W or 5W, and I read elsewhere that the system's power adaptor is 8W and I'll be using a SEGA Mega Drive adaptor which clocks in at 12W maximum output.

3) If I were to get a different version of the board (I'll update later if I do), where would the Audio and Video out points be? I asked the creator of the mod and they did say it should work with other board revisions assuming one can find the correct points to solder to.(This one might not be necessary, as I've heard the GPM-2 revision is the most commonly found one and I'm hoping that's the one I've bought, but you can never be certain and sellers never list it.)

4) Mainly for curiosity, is that seriously it??? Three caps and a resistor seems awfully simple for an output mod compared to other schematics I've seen. I really hope it works, as it's my first modding job and I would much prefer something simple.

If anybody could answer any of these I would be incredibly grateful, and it would help loads :D I didn't order the RF or power cords with the system, and having PAL TVs is a nightmare enough so I figured AV was just the best option as I definitely have spare cables lying around.

Thank you in advance!! ;D

FAMICOM_87

1) just use 2 wires for audio jack and 2 wires for video ,that all
2) the wattage does not meter, use the tiniest one resistor like 1/8 W is enough
3) the Audio is always in pin 46 from the cartage slot on any revision, but the video is not, you have to trace it down from pin 21 on the PPU
4) yes it is very simple , there is a slightly complicated scheme with one additional transistor, but is can work on any famicom NES or famicone even NOACs here
https://drive.google.com/file/d/1EQRmeMO1W0WFJ3EWKj9Z5l3DMet4eLTV/view?usp=sharing

FAMICOM_87

Quote from: SlumberingWeird on June 05, 2020, 10:26:40 amI didn't order the RF or power cords with the system, and having PAL TVs is a nightmare enough so I figured AV was just the best option as I definitely have spare cables lying around.
You are out of luck if your TV only supports PAL! TV has to be NTSC or multi-region !

SlumberingWeird

Quote from: FAMICOM_87 on June 05, 2020, 12:09:59 pm1) just use 2 wires for audio jack and 2 wires for video ,that all
2) the wattage does not meter, use the tiniest one resistor like 1/8 W is enough
3) the Audio is always in pin 46 from the cartage slot on any revision, but the video is not, you have to trace it down from pin 21 on the PPU
4) yes it is very simple , there is a slightly complicated scheme with one additional transistor, but is can work on any famicom NES or famicone even NOACs here
https://drive.google.com/file/d/1EQRmeMO1W0WFJ3EWKj9Z5l3DMet4eLTV/view?usp=sharing

This helped a lot, thank you!! I'm a complete novice, so I've no idea what a PPU even is, where a 5V line would be, or how to wire any of it up in parallel, but I'm sure with a bit of asking about I could figure it out. I'll at least be able to find pin 46 from the slot, that's easy enough and is very handy to know.

I'll probably update this thread with the PCB number I get if it's not GPU-1 or GPU-2 (As far as I'm aware they're pretty similar) and ask for a little more help then.

And no worries about the PAL TV, all the TVs in the house are fairly modern and do support a 60 hertz signal, so it isn't the end of the world if the mod fails, but my NES uses AV cables as well and I'd rather not pay more money for the RF cable when I already have at least two sets of spare AV cables.

P

The PPU is the video chip in the Famicom designed by Nintendo, possibly inspired from Namco's Galaxian arcade system (which inspired Nintendo arcade systems like Donkey Kong) and common video chips like the TMS9918. It's sprite- and tile-based and is what gives games the characteristic Famicom look.

Even if your TVs support 60 Hz framerate and NTSC colour encoding, chances that they support NTSC via RF are low. Or did you already test RF?

SlumberingWeird

Quote from: P on June 05, 2020, 11:38:06 pmThe PPU is the video chip in the Famicom designed by Nintendo, possibly inspired from Namco's Galaxian arcade system (which inspired Nintendo arcade systems like Donkey Kong) and common video chips like the TMS9918. It's sprite- and tile-based and is what gives games the characteristic Famicom look.

Even if your TVs support 60 Hz framerate and NTSC colour encoding, chances that they support NTSC via RF are low. Or did you already test RF?

That makes sense I guess, thanks.

I have tried it with PAL RF, I've an old PS2, but I don't own any NTSC systems above a couple DS consoles. I guess I'll see what happens if the mod fails.

SlumberingWeird

June 12, 2020, 04:02:13 am #6 Last Edit: June 12, 2020, 06:54:51 am by SlumberingWeird
UPDATES:

I've got myself a CPU-007 board revision. I've no idea where any of the solder points might be, or if I'll need extra parts or wires to get to or between them.

I can see five square points labelled as GND, VIDEO, CLK, VCC, and SOU, would these be the correct points? I can probably guess which is ground, video out, and audio out, being GND, VIDEO, and SOU, but I'd rather not proceed without proper confirmation. I've no idea where a "46 from the cartridge slot" is either, and my only guess at it doesn't look like it connects to anything. I should also add that I'd prefer not to cut Pin 21 as that disables the RF, and even if I don't use it I would prefer the console to still have all its functions.

If somebody could please help that would be great! (Diagrams a plus, I'm really quite clueless here  :-[ )

FAMICOM_87

give me a photo of your famicom board from soldering side and I will draw you where and what you have to solder  ;)

SlumberingWeird

Quote from: FAMICOM_87 on June 12, 2020, 10:25:31 amgive me a photo of your famicom board from soldering side and I will draw you where and what you have to solder  ;)

Thank you! This is it here, it's a Twitter link because that was easier

https://twitter.com/SlumberingWeird/status/1271536371337965573?s=20

Thanks again!

FAMICOM_87

June 12, 2020, 02:39:45 pm #9 Last Edit: June 12, 2020, 02:49:32 pm by FAMICOM_87
Here you are :) 47uF cap is optional for reducing the vertical lines (jailbars)
the caps can be higher voltages as well for example 10V if you can not find any 6.3V
The resistors are 100 ohms and 150 ohms can be 1/8 Watts or 1/4 Watts
the transistor can be any PNP
for example https://www.addicore.com/2N3906-PNP-Amplifier-Transistor-p/152.htm
Be careful for the pin out - Base, Emitter, Collector  ! diffident models have diffident pin outs !
good luck :)

SlumberingWeird

June 12, 2020, 03:00:24 pm #10 Last Edit: June 12, 2020, 03:07:52 pm by SlumberingWeird
Quote from: FAMICOM_87 on June 12, 2020, 02:39:45 pmHere you are :) 47uF cap is optional for reducing the vertical lines (jailbars)
the caps can be higher voltages as well for example 10V if you can not find any 6.3V
The resistors are 100 ohms and 150 ohms can be 1/8 Watts or 1/4 Watts
the transistor can be any PNP
for example https://www.addicore.com/2N3906-PNP-Amplifier-Transistor-p/152.htm
Be careful for the pin out - Base, Emitter, Collector  ! diffident models have diffident pin outs !
good luck :)

Thank you so so much!! I think I'll try it without the 47uF first, but I can always change that if it's bad. I'll order the parts and get on it, and will give a small update on how well it goes!

The smallest capacitors I can find are 16v, would those work?

Thanks again!

FAMICOM_87

Yes of course, any voltage above 5 V will work for the Caps on the board :)
you can search for any other general purpose PNP transistor (even you can use the same model on the board) if can not find that from my example. Yes you can add this 47uF temporary to see if there any improvement for you and if you are not satisfied remove it :)