Famicom AV Modification / Mod

[milkmanv1]

Ok guys, I bought my first famicom off ebay, AV modded of course, not too long ago, and It just got here today. I plug her in and...the picture seemed really dark, with REALLY weird colors, for some games it almost looked like the 3d effect you'd find in 3d world runner, or that one racing game. So anyway, not only that, but theres no sound! I thought it was my AV splitter box, so I tried it in my TV directly, nothing. Now's where it gets really weird, It works on EVERY TV BUT MINE! I have a 32 inch HD tv, I dont know what that has to do with it but it works on my flatscreen HD Sony computer moniter... (i think the moniters like 20 inches or so) as well as my sister's CR TV I took some pictures for you guys, and I have a picture to compare tower of druaga (regular screen cap) and how it plays on my system on my TV....

Heres the ugly tower of druaga



Ugly Taru-ruto kun in fantastic world title



Normal tower of druaga



Now the camera made it seem alot better then it really is, but once again theres NO sound and a weirddd picture.

[Thrillo]

I ran into the same problem with a heavily modded NES I had, or maybe it was a Famicom I can't remember for sure. The TV I was testing it on reacted the same way yours did and I tried everything to get it to work properly (tons of resoldering) until I happened to test it on another input and it worked fine. It was probably due to the capacitance of that particular A/V input or something like that.

[133MHz]

Interesting reading material (Japanese):

http://www002.upp.so-net.ne.jp/jsrc/densi/fcav2.html

From what I understood thanks to Google Translate, the guy actually observed the video signal from the Famicom on an oscilloscope and carefully designed a circuit that generates an accurate composite video signal, therefore providing the most high quality video output you can get from the red-white machine.

The circuit is a little more complicated than the one we're used to here, but the increase in complexity gets you a more accurate and thus higher quality video signal. This might solve the problems that some people have with the picture being too dark or too washed out on some TV sets, since the simpler version of the circuit does not generate a 100% accurate composite video signal, which could make some TVs upset.

P.S: Manuel, if you've got some time to spare, please give it a quick reading and give us some of your insights (mostly regarding the accuracy of what I understood ).

[b1aCkDeA7h]

That's the mod I did, its a bit bright so I may add a resistor into the mix. First though, I need to check the RF module and see what's causing this strange buzz or hum.

[b1aCkDeA7h]

Turns out the mic is shot in the second controller. Lets try cleaning that and as for the worst case scenario, replacing the second controller.

Gotta love it when it turns out to be a very simple problem rather than a more complicated and potentially painful suspect (main filter capacitor, voltage regulator).

[paletti]

Found out that I connected the audio signal to the wrong point on the board, audio + video is working fine now  New instructions can be found at  http://www.signsofshift.com/gfx/famicom.jpg

Hi guys the older link doesn't work anymore so I'd thought I'd update it, good luck with the modz!
http://img534.imageshack.us/i/img0004sp.jpg/

[an-cat-max]

whatever happened to the tutorial in the workshop section?

[UglyJoe]

It had some inaccuracies so we didn't bring it over to the new design.  A better article is planned.

[an-cat-max]

ahhh cool! thanks very much, very new to the forum but i love it already

[b1aCkDeA7h]

It had some inaccuracies so we didn't bring it over to the new design.  A better article is planned.

That's good to know, especially with the different boards and such.

[sparky]

Quick question: If you tap the video directly from the motherboard without the built amplifier do you get any picture or will the signal be too low to operate?

I recently picked up a Famicom but haven't had time to buy the components for the circuit so I just tapped the video directly into a phono jack to see if the system was working but I only received a brief discolored and out of sync image then the screen went blank and stayed in the television input screen.

Is it normal not to receive any video without the amp in between or must it be there to get any type of picture? I will be buying the components this weekend but my impatient self just had to give it a try.

Thanks

[133MHz]

Quick question: If you tap the video directly from the motherboard without the built amplifier do you get any picture or will the signal be too low to operate?

The picture will be really dark and most likely out of sync, but depending on the TV it should be recognizable.

I recently picked up a Famicom but haven't had time to buy the components for the circuit so I just tapped the video directly into a phono jack to see if the system was working but I only received a brief discolored and out of sync image then the screen went blank and stayed in the television input screen.

It seems that your TV is blanking the video because the signal doesn't meet proper voltage standards. An older TV, especially one that doesn't mute or blank the video when there's no valid signal present should be able to display the Famicom's unamplified video signal. Newer TVs just give up on anything that's too faint or noisy.

[sparky]

Interesting! I guess I should just wait until I have the proper components to work on the amplifier and see what results I get from there. Thank you for the reply, I appreciate the help.

[sparky]

Okay, having some problems here. Built the amplifier and got a steady, bright picture. The problem was there still was no sound wired up and it was a mess of wires. I mounted the mono jacks on the side of the Famicom and put all the wires in place.

I don't remember exactly how I had the wiring done previously coming off the motherboard but I tried my best to remember. At this point I only get sound now but no picture! Very strange but I assume it's a grounding issue. Any ideas why I get sound but no picture?

It's like my previous post again where I see a faint image and it disappears. I'm going to spend more time on this tomorrow and see what it leads to.

Thanks

[ericj]

Could someone post the schematics or tutorial that used to be on the site? Thanks!