Video EMI / Noise on Famicom

[Niku-Sama]

ok i dont have it here yet but its on the way.

i recently won an auction on ebay for a Famicom, $13.06 (cost more to ship the thing) no ac adaptor or rf unit which is no biggie as i have them already from a previous famicom adventure that when i got home i decided i did not want to open.

any way the listing for the auction says this


This item is Secondhand.
Condition of Console: some tiny scratches/No AC adapter
Condition of Box: No Box
Condition of Instruction: some tiny scratches
Other: a game cannot be displayed properly on a TV scree/Noise


so it works but its got some EMI from something. could be from the PSU they were testing with or the RF unit but either way it works but aparently has some static issues so when it gets here what should i try first if it turns out to be something other than an RF unit or AC adaptor?


some hints on model. it has a shiny bottom, but round buttons with a blue cartridge slot. this is an odd one aswell, player 1 controller looks flawless where player 2 controller looks beat to hell, obviously been serviced before.
it just shipped today but its shipping EMS so it wont take long before it arrives, i missed my other auctions so i had a few bucks left over so i figured why not EMS? every other time i have shipped EMS its taken 3 days, so fast that the tracking cant keep up.

[ApolloBoy]

The RF unit might be out of alignment from the sound of it. Honestly I'd have it AV modded and you won't have to worry about static ever again

[Niku-Sama]

I was considering that, could do stereo and take advantage of the better sounding games too. Was a cheap enough console. Either way I want to pin the problem down before I mod it.

Do if not a bad rfu then maybe a re cap is in order?

[Niku-Sama]

ok i got my famicom today and woah boy its got a problem.

it seems to be isolated to outputing the video and audio because you can tell its on and trying but its very staticy and rolling. i pulled the mobo and other pcb (what exactly do i call it?) out and most everything seems fine.....

some info:
HVC-CPU-05 revision
in a smooth bottom case
NES RF unit tried on channels 3 and 4, 15 and 95 / 96 both cable and antenna on a sony trinitron 19inch
the sony works with foregin units, my twin famicom works on this set
aftermarket PSU, bought in japan at super potato as a famicom replacment a few years ago, has always worked for other systems
it is a shiny bottom famicom however it seems to me it was one that was serviced once before, it should have square buttons and an older mobo revision considering the serial number

its pretty clean on the mobo, it seems that capacitor labled C8, its a brownish yellow cap that looks like a pill may have leaked, theres some stuff on the PCB underneath it...which is odd considering the make up of the part, the rest of the caps seem fine, no evidence of leaking

[Pikkon]

If anything I would av mod it,that would completely bypass the rf.

[Niku-Sama]

I'm thinking about it. If I do I'm going to replace the whole power / t.v. board with one I make. I just want to get rf working so I have one to use until I finish the pcb design for such a thing.

I figure av mod with stereo out and a little added protection and EMI filtering on the power input plus adjustable levels on sound channels

[Niku-Sama]

alright i have poked and proded enough to get it to the point where i can tell everything is working well enough to see thats its only audio and video output being the problem.

heres what i want to do, its different than other mods that i have seen but i want to replace the power / RF output board with one thats better designed and geared tward Composite and stereo with (maybe) room for a S-Video mod in the future.
its alot of work and i'm sure i'll need a bit of help from various forums on what amps and filtering methods to use but its doable and frankly cleaner than the other mods i have seen.

the biggest reason for doing it is it would be cleaner, instead of running wires to a 3rd home made perf board you'd run them through most of the existing connections, maybe run some jumper wires on the underside and contain it all on the power board and thats the other reason i want to do this, if i can get it all onto the power board then i will be able to tap directly into incoming power to run the amps to clean up the audio and video signals, but of course i would run the power comming into the board through a better EMI filter. i managed to get my scope working with some funky home made probes for a moment and it was noisier going into the main board than i expected, even with a new 3rd party unit.

but first things first, does any one know where i can get a translated wiring diagram and/or pin out location sheet for the famicom main board?