Famicom av mod instructions?

[leonk]

I got a famicom in today for repair. Customer used AC/DC wall wart with reverse polarity. I do a lot of USA top loader AV mods so have lots of those amps on hand. So I lifted pin21 on PPU and connected amp. I was getting only B&W image.

I recall someone saying in another old post that this happens with a bad crystal. Famicom and NES use same freq of crystal so I replaced it with one from my parts bin. I got nice clean video with no jail bars.

Which makes me come to my question: if the PPU between NES and famicom puts out the same NTSC signal then why not use the same amp? Hundreds of people have successfully used the nesdev forum top loader amp schematics (which look different from the ones found here) with 0 jail bars.

I'm not as experienced with famicom as I am with NES and was just wondering.

[number47]

You can use whatever amp you like.

[number47]

Just finished my mod according to this sketch. The board is HVC-CPU-GPM-02D. I can see slight bars only in SMB sky.

[zmaster18]

I don't know if this was confirmed here, but I can say that Famicoms with the PPU that has a metal plate/heatsink on top gives out lots of jailbars, even if you isolate pin 21 and put the caps on the underside of the board. I've done 3 Famicoms with this type of PPU and they all had this problem. Every other one I have done had good quality video with just faint jailbars on light colored backgrounds only.

[jpx72]

My experience preffers the GPMs (with metal shielding on cartridge connector). I was able to de-jailbar every GPM so far really nicely.

[leonk]

Last year I modded 2 Famicom systems to add AV support.  One of them was a Hong Kong special where it was modified to be PAL back in the day.  Given these systems are now in North America, I undid a lot of the PAL conversion back to standard NTSC.

I was surprised to find that the stock famicom had jailbars, while the Hong Kong special was 100% jailbar free.  The only difference is the power side.  The modified version used a 3rd party power board with a lot less components.  I believe the only way to rid of jailbars forever is to create a new PCB with redesigned power and audio amp.  This is similar to what Tim W did for the NESRGB Famicom kit.

[Farid]

What is the best replacement for 2SA937?
Can I use A733?
What is the most recent and best schematic for AV mod?

[famifan]

What is the best replacement for 2SA937?
Can I use A733?

any general purpose PNP transistor will work like a charm. there's no specific requirements from that part of scheme.

thus, a733 is perfectly fine.

why are you asking?

at least, the jailbars don't depend on transistor model anyway.

[Great Hierophant]

I have been trying to make sense of this page : http://vaot.mydns.jp/fc/noise4.htm for advanced jailbar removal on an HVC-CPU-07.  It seems to be telling me to do three things.  First, to lift the pin of either the CPU or the base pin of the Q3 transistor out of its hole.  I would prefer to do the latter rather than cut or risk destroying a PPU pin. 

Second, add extra capacitors, 2.2uF, on the underside of the board wherever you can find an area where there is are a pair of conveniently located solder points between the voltage and ground planes.  I think he scrapes up some of the planes to solder the capacitors, but I don't believe that will be necessary. 

Third, he adds a 330uF/16v Conductive Polymer Aluminum Solid capacitor between the ground pin of the PPU and a nearby spot on the voltage plane.  I believe the ground plane goes to the negative lead of the capacitor, which is marked by a purple semicircle on top of the capacitor. 

Is there anything else to be noted?  Do I have this right?

[80sFREAK]

THIS. For those, who want to try pseudo stereo.

[VegaVegas]

Did anyone have ANY success reducing jailbars on HVC-CPU-07 board with RP2A03E + RP2C02E?? At this point I have tried everything, soldering OS-CON 330uF 16V between PPU 5V and GND, installing 4x 220uF capacitors between PPU 5V and GND, installing many ceramic 2.2uF caps in all possible places and I had NO improvement whatsoever... First of all, yes I have lifted pin #21 PPU and base of Q1 transistor and connected them directly and even after that I don't think the picture improved in any way. Those jailbars are so noticeable and I think the only solution is to live with them, I have spent hours and hours to make it look better but it's so stubborn the picture just refuses to look clean...

[Pap]

hello, im new to the forums.
as i travel from time to time to japan i have frequent ocasion to buy original famicoms, naturally i wanted to start av moding i followed the guide on jpx72's blog site but i have some questions, sorry if the answer is here but reading thru 22 pages of posts is quite challenging:)
1. i cant seem to find 33uf ceramic capacitor, the owner of my local electronic shops says they dont make ceramics ones of that value, so my question: is there a mistake of suggesting ceramic one or a mistake in value?
2. the same issue for 1uf ceramic capacitor, maybe mistake in value on the blog?
3. can i desolder and remove the RF output cinch completely? do i have to bridge something on the rf board to do that? or should i not touch it and just put a pair or another cinch ports next to it? for video and audio