Possible issue with my (RF) Famicom console.

[Kirito]

I just recently bought an original Famicom from Japan, and upon loading up Super Mario Bros I noticed the verticle lines, which I gather are "jailbars".
I'm only familiar with the US toaster NES, so I've never seen the jailbars before, but I have done some searching and found mostly information about the US top loader has jailbars due to some odd design flaw or something like that, but haven't found much on the Famicom for some reason, possibly because they usually get av modded, etc I assume.

My question would be, is that just normal for the Famicom to have those jailbars, and does it just suffer from the same type of design flaw as the US top loader?

Just curious as I've been a bit worried that I might have bought a bad Famicom console, so I just wanted to find out if that's normal.

I took a pictureof the bars that I'm seeing when I play a game.

http://i.imgur.com/brSPta5.jpg


Thanks for any info, it's greatly appreciated.

[rainwarrior]

Yes, I think that's a common problem.

[Drew Sebastino]

Do you know exactly what causes the problem? I think I've heard it has something to do with cheaper video hardware parts than the original system.

[Memblers]

Based on others' experience with modding the system, it looks like it's mostly noise picked up from PCB routes that are near the PPU's video out pin/route. The fix is lifting the video out pin from the PPU and running a wire from it. If you reattach the signal to the same PCB route at a different point on the board, you'll also need to cut the PCB trace in a couple places.

[tepples]

Would it help to replace the main bypass capacitor and the bypass capacitor nearest the PPU? Or are jailbars not related to dirty power?

[lidnariq]

Based on the number of people who have successfully fixed it by rebuilding the video amplifier (instead of recap'ing their famicom), it's apparently usually capacitive coupling rather than the power rails.

[Memblers]

I've seen several people also say that adding a capacitor (1uF or bigger) between pins 20 and 22 of the PPU is helpful, but apparently it's not as effective as lifting the video out pin (of course, you can do both).

[Kirito]

My Famicom is unmodded (since I had no issue getting Channel 95 to work and for me the picture looks good I haven't thought about modding it at the moment), but all I can really find was a short video on youtube https://youtu.be/kjk6vjnf1BE that mentions it's some design flaw with early Famis and NES top-loaders, so I guess all that may be what's causing it is maybe noise from one of the traces close to the pin

I've never seen that before, and I'm using a Model 1 Genesis adapter to power it (9V DC 1.2A output so I know it has pretty much the correct power input), and using the RF box from my old toaster style nes.

Kinda freaked me out when I first turned it on and saw those jailbars, thought I had gotten a faulty famicom, but I guess it sounds like that it must just be normal for the pure "stock" console to do that then.

[wyatt8740]

I've got a famicom and previously had a top loading NES as well.

I found that the noise seemed to be coming from the ram chip just above the PPU's pin 21 on the board (using the extremely scientific method of putting my finger between the pins of the PPU and ram chip to act as a capacitor). No way to totally get rid of it without retracing some of the board, I think (lifting the ram out, cutting traces, finding where the traces went to), but I have reduced them significantly by lifting pin 21 off of the board and cutting the trace on the board that leads from it to the transistor. If you want to keep RF, run a wire from the lifted pin to the Q1 amplifying transistor. Otherwise, you can follow the same steps as the NES top loader AV mod for composite out.

Remember, this does not get rid of them. It just makes them less visible in most games.

Got another famicom motherboard in the mail the other day, and the jailbars are more visible on RF than with pin 21 lifted on my AV modded one.

The toaster (front loading NES) has jailbars but they are very very faint. You can see them playing some games like RC Pro Am or even Mario 3 if you look closely at the sky. I never noticed before I got a top loader and knew what to look for to find jailbars.

[Kirito]

I think I've somewhat gotten used to them now, when I got into the Famicoms I hadn't realized how the board was designed, and I'd mostly read about the
US top-loader and its problems, but hadn't seen much about the Famicom.

They probably show up so well because I do play on a Plasma TV and not a CRT, but, aside from the jail-bars, which now that I know they are normal do not really bother me, the RF picture quality is actually about what I remember on the toaster NES I had as a kid, other than the whole using a CRT back then as opposed to a Plasma now.

At first glance I'd feared that I had gotten a broken console and it just wasn't labeled as such when I bought it, but learning what Ive learned since then I feel much better about it. I may consider modding it a bit in the future to try and reduce the jail-bars some, while keeping the RF (since the RF quality seems just fine, to my eyes anyway) but I'm not confident enough in my ability to really mess with it, so I may just leave it original and just enjoy it the way it was made (or I may have to find a good A/V modder in the future and consider having it A/V modded with a 3.5mm jack in place of the RF jack).

[Ziggy587]

I've never seen that before, and I'm using a Model 1 Genesis adapter to power it (9V DC 1.2A output so I know it has pretty much the correct power input), and using the RF box from my old toaster style nes.

Is that an official Sega brand power adapter?

I never had a (noticeable) jailbar problem with my Famicom. I once tried using a different power adapter (some cheap no-name junk) and not only did I get noticeable jailbars, I got a slight hum in the audio too. So from my own personal experience, the power adapter you use definitely matters.

I may consider modding it a bit in the future to try and reduce the jail-bars some, while keeping the RF (since the RF quality seems just fine, to my eyes anyway) but I'm not confident enough in my ability to really mess with it, so I may just leave it original and just enjoy it the way it was made (or I may have to find a good A/V modder in the future and consider having it A/V modded with a 3.5mm jack in place of the RF jack).

I don't wanna push you to modify the console if you're not confident enough to do it, but I just thought I'd mention... When I modified my Famicom for composite video, I didn't notice nearly as much of a difference in video quality as I did with audio. The video might as well looked the same, but the audio was a massive improvement. It's much more clear, you don't realize how muffled the RF audio is until you hear the difference.

[Great Hierophant]

For Famicoms with the HVC-CPU-GPM-02 boards, essentially the late Famicom boards, this page has a few ideas on how to reduce the jailbars :

http://vaot.mydns.jp/fc/noise5.htm

What I can make out from that page is that lifting pin 21 from the PPU is necessary for significant improvement. You also need to lift the base pin of the video amplifier transistor as well if you are going to use that.

There are two other things I believe he is trying to say. First, replace 11 0.1uF capacitors with 1.5uF capacitors at the locations marked on the board at the bottom of the page.

For the HVC-CPU-07, it is a lot more difficult to determine what he did :

http://vaot.mydns.jp/fc/noise4.htm

Obviously he lifted PPU pin 21 and the base pin of the video amplifier transistor. Then he appeared to add a bunch of 2.2uF surface mounted ceramic capacitors around the solder side of the PCB.