Famicom av mod instructions?

[kyuusaku]

Thanks kyuusaku, can't argue with that, but:

-create filters which reduce the horizontal resolution
-create filters which result in the loss of color information
-amplify the signal and brighten the image
-attenuate the signal and darken the image

-this is what we're trying to do and as you can see we are not good at it. If you want to be of help, propose a schematics to built those. I think everyone involved would be really gratefull if you do that. Really. Please.

I posted what I believe is the best circuit 1 page pack. It's a single PNP, 2 resistors and 1 cap. Since I posted that I believe it's better to switch the position of the output resistor and capacitor.

[jpx72]

So this is it: (attachment)

zmaster18 - try to build this one. Use the S9015 transistor (PNP).

[zmaster18]

Ok, so I played around with the circuit, and got video that is 90% accurate. I'm satisfied with it.

Now, my next question: I used a Nintendo AV connector from a Gamecube. I want to mount it right where the TV/Game switch is. How do I go about removing parts of the RF Modulator? I don't need to have it working, since it doesn't work anyways. My Famicom is HVC-CPU-007.

[jpx72]

kyuusaku I have built your simple schematics and can confirm that it works better than any other experiment. But the vertical bars are still a problem (even if using fully shielded cables and everything is built right on the PCB of the famicom so really close together to minimise interference). But by adding the 500microF capacitor between PPU's GND and VCC pins the problem disappears.
(I have also updated my page with that schematics, I hope you won't mind http://www.jpx72.detailne.sk/modd_files/fc/avmod.htm)

[armando2002]

I just completed jpx72's AV mod with success! I'd like to suggest that someone add the wattage and voltage requirements for the various capacitors, resistors, etc. as I had to buy several sets to get them to work. Eventually I used 1/2 watt for the resistors and 25V for the main capacitor and it worked just great. Thanks!

[Da Bear]

I also made this mod and it's working great! I didn't put a capacitor over the PPU since it didn't make any difference.

[jpx72]

Thanks, but it was kyuusaku that made that schematic, I only put it together with some explanatory pictures...
So give him credit as deserved, and meanwhile - great work guys and thanks for the feedback!

[Da Bear]

Okey, so I have done a slight modification to this mod.

First I used a 2N3906 PNP transistor as kyuusaku suggested earlier in this thread. The mod worked great with this, but not good enough (slighty blurred image and 'jailbars')

So, I desoldered the 2SA937 from the Famicom(Q1 next to PPU) and replaced my 2N... with the 2SA...
Next I cut the trace from PPU pin #21 and Q1. I cut it in both ends.

Result:
# Crisp and clear image, no blur whatsoever.
# No more jailbars! Yey! If you know they are there, you can see them - barely. Almost completely gone! No need for capacitor  over the PPU!

Try it! No need for RGB mod

[jpx72]

Well that's good for you!
Maybe cutting #21 and desoldering that transistor does help because I tried this mod without desoldering the 2SA937 (Q1) from the board, I used this transistor directly, I just cut the emitor and continued with the rest of the schematics from there (collector is already on GND and #21 is on base) but without luck in better image.
It all depends on the whole thing built, the quality of soldering etc. And of course on the mainboard model. By the way, which board do You have?

[Da Bear]

I have a 02F board.
First I just cut the trace without removing the 2SA937, but that alone didn't do anything to reduce the jailbars. It was after I removed 2SA... the 'jailbars' was heavily reduced.
The reason for this is as I understand, that the trace from #21 to Q1 picks up interference from the databus right below.
And it's possible that the 2SA937 isn't so sensitive to interference as the 2N3906 and it's equivalents.

Here are some images, I know some of you (including me) want see what we're talking about

First the location of Q1 seen from top, here I have already removed it but it's easy to locate.


Here you see wich trace to cut. Be careful so you don't cut any other trace as this will destroy your Famicom.
I scraped the trace in the middle and used a multimeter to make sure the trace was really disconnected.


Not the best image, but here I have replaced my 2N... with the Famicom's 2SA.


Be aware that doing this will permanently disable RF output from your Famicom!

[jpx72]

Great pictures, thanks for sharing! I will definitely try it!

[Da Bear]

Did some more testing today.
Tried several caps over the PPU without any luck reducing the vertical lines.

BUT! I had the machine laying upside down with the gut open towards me, and for some reason I tried lifting the wire running from #21 off the board, and the lines became almost completely invisible!
So, I extended my wire (the green one in the pictures) and placed it next to the board instead of running it straight over.
I also resoldered it to pin #21 making it point up more. Success!

In SMB1 I only see something that looks like lines when I'm in the swimming levels. In SMB3 you can see them if you really want to.

Right now, I can't think of anything more you can do besides using a shielded cable instead.
There is interference from both the PPU, CPU and connector traces that the wire can pick up. So avoid them as much as possible and secure the video wire with some heat glue.

[mamejay]

Excellent Da Bear.
I have done a few of these mods but will give it a try using your method.
One thing I noticed.  You cut the track from Pin21 but from what I can see once you remove the 2SA937 that track foes nowhere.  Do you need to cut this trace?
Looking at the top picture you can see that it goes nowhere.  i could be wrong.

I am finding that the picture is not as bright as it could be.  Is there any way of boosting the picture quality on this one?  On my 80cm TV it looks a bit dull.  On my 51cm TV it looks pretty good.

I will try this on the next console and compare the results.

[2A03]

I tried Da Bear's method on my top loader and it's definitely an improvement over kyuusaku's original circuit. The video quality is slightly better than with the 2N3906, though I'm still getting the vertical lines. However, the lines aren't as visible as they were with kyuusaku's circuit. Although instead of cutting the trace to pin 21, I lifted the pin so that it would be completely isolated from the motherboard.

[Da Bear]

Glad to know it's working!

It's probably not neccessary to cut the trace if you lift pin #21 from the board and run the wire on top of the board.
But if you don't lift #21 And don't cut the trace, it will pick upp interference from the traces that runs below thus giving vertical lines. Think of the remaining trace as an antenna.

A shielded cable running as far away from the board as possible is the last thing to do to eliminate contamination of the video signal.

Are you sure the brightness setting on the TV is correct? I have 3 TV sets that I have tested my FC on and it looks great on any of them.
1 Samsung 32" Wide CRT
1 Panasonic 32" Wide CRT
1 LG 50" Plasma

Sample picture taken on my Plasma:



Post Merge: October 01, 2011, 02:13:29 pm
Today I changed my green videosignal cable to a shielded cable. I grounded the cable shield at PPU #20 and at the collector of the transistor.
The result is 99% perfect picture. I think this is the best it can get without rewiring the PPU completely, and I'm not going to do that!

This is what I have done to my poor Famicom
* Buildt kyuusaku's video curcuit using the famicom 2SA937 transistor. It's located near the PPU and is marked as Q1.
* Desolder Q1 and cut the trace from PPU #21 to Q1. Cut it in both ends as close to #21 and Q1 as possible. (If you don't want to cut in your board, you need to lift pin #21 from the board isolating it.)
* Used a shielded cable that I grounded to PPU #20 and the collector of the transistor.
* I have placed the video circuit at the RF box (Next to it, not inside ) as there is the most space there. Just keep in mind that you need to run your shielded cable around the board and not straight over it to minimize contamination of the video signal.
* And to finish it of, I have secured my wiring and my circuit with hot glue.

I have done this on a 02F board and I'm gonna try it on some older ones to so stay tuned for that