Questions about Jailbars

[Great Hierophant]

Akumajou Densetsu shows a small amount of jailbars on my Famicom AV.  They are really only noticeable in dark green colors, such as the tree tops in Stage 3.  Castlevania III: Dracula's Curse does not, even through a pin converter.  I would guess this is because the Japanese cartridge is producing some noise due to the expansion audio or the poorer build quality of Konami's cartridge PCBs compared to Nintendo's.  I also can notice jailbars with a Famicom AV and a PowerPak and Everdrive, but the jailbars are as about as prominent on an Everdrive as they are on the real Akumajou Densetsu cart.  You may see one capacitor on a Konami board whereas you would see three on a Nintendo board.  Do other Famicom cartridges not produced by Nintendo exhibit more noise in the video output? 

Dark green colors are often the best candidates for visible jailbars.  The game Lunar Pool is a good game to use because the billiard table uses green and takes up most of the screen.  I don't have a real cartridge of Lunar Pool or its Famicom version Lunar Ball. 


Do earlier Famicoms show more prominent jailbars than later Famicoms?  The later Famicoms were designed to meet stricter EMI standards.  They have more noise filtering capacitors and shielding, although the placement of the chips did not really change.  What about after an AV mod, can anyone who has experience with both varieties of Famicom say whether one type is more jailbar friendly on the better quality output?

Finally, can anyone claim that their AV-modded Famicom shows no more jailbars than a Famicom AV?  Is the copper shield mod, which requires desoldering the PPU, sufficient to bring a Famicom to the level of a Famicom AV?  Is anything?

[hvc01]

in order of best picture from my experience only which means nothing in terms of science as it is all anecdotal

av famicom > av mod famicom > twin famicom

it is variable also and probably depends on the age of the components both in time and how they were stored used during their lifetime.

others will chime in no doubt but the best way i have found to get rid of them or reduce them is chase a system with less jailbars if it is bothering you and stay away from twin famicoms at all costs

[jpx72]

Copper shield mod is like 5-30% jailbar removal of the complete AV mod. So not really that worthy of all the trouble.
It may be not sufficient to remove CPU and PPU and put them in a completely new board designed against jailbars. It's old technology, don't search for perfection!

[80sFREAK]

If you want perfect things, you have to do mod proper.
Why i did shielding? It is not that complicated and working well as base for videoamplifier.

[Great Hierophant]

If the copper shield is what it takes to get to Famicom AV levels of jailbars, then it may be worth it. 

It would be interesting to see how a front loader NES compares with a copper-shielded AV-modded Famicom.  Perhaps a copper shield on the NES's PPU may help to reduce its jailbars (which are pretty decent).

[80sFREAK]

It is NOT ONLY shield, but ALL TOGETHER.

[fredJ]

Akumajou Densetsu shows a small amount of jailbars on my Famicom AV.  They are really only noticeable in dark green colors, such as the tree tops in Stage 3.  Castlevania III: Dracula's Curse does not, even through a pin converter.  I would guess this is because the Japanese cartridge is producing some noise due to the expansion audio or the poorer build quality of Konami's cartridge PCBs compared to Nintendo's.  I also can notice jailbars with a Famicom AV and a PowerPak and Everdrive, but the jailbars are as about as prominent on an Everdrive as they are on the real Akumajou Densetsu cart.  You may see one capacitor on a Konami board whereas you would see three on a Nintendo board.  Do other Famicom cartridges not produced by Nintendo exhibit more noise in the video output? 

Dark green colors are often the best candidates for visible jailbars.  The game Lunar Pool is a good game to use because the billiard table uses green and takes up most of the screen.  I don't have a real cartridge of Lunar Pool or its Famicom version Lunar Ball. 


Do earlier Famicoms show more prominent jailbars than later Famicoms?  The later Famicoms were designed to meet stricter EMI standards.  They have more noise filtering capacitors and shielding, although the placement of the chips did not really change.  What about after an AV mod, can anyone who has experience with both varieties of Famicom say whether one type is more jailbar friendly on the better quality output?

Finally, can anyone claim that their AV-modded Famicom shows no more jailbars than a Famicom AV?  Is the copper shield mod, which requires desoldering the PPU, sufficient to bring a Famicom to the level of a Famicom AV?  Is anything?

I think later model FC have less jailbars, yes, but earlier models can also have few jailbars if they are in good condition.

Generally it depends on how used the console is. Jailbars are caused by interference that gets picked up here and there.

I'd say a good famicom mod on a good fc console is almost the same quality as the New Famicom, but I only play on my old fat TV. Can't say on a new plasma TV. If you are extremely picky then don't expect perfection with a famicom mod.
You can check out a demo video here: https://www.youtube.com/watch?v=dudJ-hywkI8
Here is the same mod on a different console: https://www.youtube.com/watch?v=npADP9U5z6Y

[chowder]

The original Famicoms differ so much in regards to different PCB revisions, and sometimes just individual consoles, that I don't think a mod that is guaranteed to work for ALL of them to give AV-Famicom level video quality is even possible.

I've had this discussion with jpx72, we think it's probably likely that there were several factories using whatever parts they had to hand at the time, because there is very little consistency with some of the components they used, even on boards that are the same revision.

I've noticed that power supplies can have an effect, especially when Powerpaks/Everdrives are used.  Better quality ones with higher amperage output seem to result in less jailbars.  I'm not an EE, so I can't explain that one

[80sFREAK]

I think someone want step-by-step videomanual how to mod any famicom to the perfect Trust me, the mod is EXACTLY same for ANY revision PCB.

[chowder]

I think someone want step-by-step videomanual how to mod any famicom to the perfect Trust me, the mod is EXACTLY same for ANY revision PCB.

The exact same results for any original Famicom?  I eagerly await your video

Most of your other solutions seem to involve chip shielding and throwing as many capacitors as possible at the board.  As I understand it, the problem mainly stems from the grounding layer of the PCB, but I guess the video will explain how your solution fixes that.

[Great Hierophant]

I understand the principle and do not need a video.  Perhaps the NESRGB would offer a jailbars free solution.  Anyone notice any after modding their system, especially with the native composite video?

[80sFREAK]

I think someone want step-by-step videomanual how to mod any famicom to the perfect Trust me, the mod is EXACTLY same for ANY revision PCB.

The exact same results for any original Famicom?  I eagerly await your video

Most of your other solutions seem to involve chip shielding and throwing as many capacitors as possible at the board.  As I understand it, the problem mainly stems from the grounding layer of the PCB, but I guess the video will explain how your solution fixes that.

Caps are dirt cheap and, actually, i ended by adding only 2 ceramic and 2 electrolytic on the PCB.
Yes, grounding and PCB itself. IIRC, when you desoler pin 21, transistor and measure capacitance between this trace and "next door" traces, it was about 18-20pF, which is quite big for videosignal. Grounding is the part of original videoamplifier, so whatever signals(in the ground plane as well) arounds, they gonna be in your videooutput.

One more hint. Famicom have non-detachable controllers, so why bother with detachale AV cable?

[Protoman]

My Twin Famicom looks better on a HD TV than my av mod Famicom

[chowder]

One of my friends brought his AV Famicom around, and his has noticeable jailbars.  Faint, but there.  My own AV Famicom on the same TV (and same AV cable) doesn't have any at all...  We took them apart, seem a similar age, no differences that we could see, just one has jailbars and one doesn't.  I give up trying to figure it out, it seems to be quite random.  Deteriorating caps in his unit?  Everything checked out OK multimeter wise.

[Great Hierophant]

One of my friends brought his AV Famicom around, and his has noticeable jailbars.  Faint, but there.  My own AV Famicom on the same TV (and same AV cable) doesn't have any at all...  We took them apart, seem a similar age, no differences that we could see, just one has jailbars and one doesn't.  I give up trying to figure it out, it seems to be quite random.  Deteriorating caps in his unit?  Everything checked out OK multimeter wise.

When comparing your two systems,

Were the motherboard revisions the same?  The Famicom AV has HVCN-CPU-01 and HVCN-CPU-02, and the 02 has an extra electrolytic capacitor at C14 and uses a BU3270 instead of a BU3266 at U3.  

Were you using the same cartridges?  I have noticed that Nintendo manufactured-cartridges appear to be noise free, but other companies' cartridges can induce more noise.

How did you test the caps?  Without removing them, the reliable way to test them is by using an In-Circuit ESR meter, and they are expensive.  Also, the brand manufacturer of the caps may be different between the two boards, and some brands have better noise characteristics than others, so I have read.  

Also, make sure you are using the same power supply brick.  A poor quality or failing power supply can add noise to a console's video and audio output.