RGB PC Engine Jail Bars

[broken]

I laugh at the notion that the RGB amp has any bearing on the jailbars.

Pro tip: it doesn't.

It certainly has some level of bearing on the final RGB output though! Guess you have no experience with the AV-DRIVER. I've tried all the other amp designs, and when set correctly, it does the best job!

The only bearing it has is how well the RGB levels are amplified (video quality in general). The jailbars are being generated at the 6260 level. That's why they are still there even with the stock composite video. However due to composite's nature, they are (somewhat) masked.

Console lottery and display has more bearing on if you notice it or not.

Are you suggesting it's an issue with the Hu6260 ICs or the circuit used in different console revisions?

Yes, that is what I am suggesting. I have modded a number of PCE units and built several amp designs and in my experience White PCE units display the least noticeable jailbars. Where as the TurboGrafx16 has some of the worse. Duo's in the middle. The Supergrafx tends to have some bad ones.

Thesteve has provided some remedies that greatly reduce jailbars.

"thesteve" has also designed a god awful RGB to component circuit that has failed two Kickstarter campaigns. Mixed bag?

And? I see no correlation between the two. He found that if you strap some extra capacitance between pins 41 and ground and pin 43 and ground on the 6260, the jailbars are greatly reduced. I have done this to several consoles and it indeed helps. Especially on Duos. Also, on Duo-R/RXs if you replace Cap C961 with something like a 220uf it also helps reduce it even further. On a TG16 replacing C142 helps.

http://pcengine.freeforums.org/jailbar-fix-t233.html

http://www.pcenginefx.com/forums/index. ... #msg204771



I am 100% confident that no amp design by itself will eliminate jailbars. This is a problem that needs to be tackled at a system video level prior to any kind of amplification.

[kamiboy]

All these conflicting reports of which PC Engine revisions are affected the most is throwing a big old monkey wrench into this investigation.

Since the absolute most problem free image quality out of a PC Engine that I have personally seen with my own eyes was a from a white PC Engine while myself owning both a problematic PC Engine Duo and Core Grafx, I am going to trust the following conclusion.

The white PC Engine is the best common Japanese hardware revision for RGB mods. That being said I have yet to personally see an RGB modded Core Grafx II, LT, R, RX or Shuttle, nor any overseas revisions for that matter. Fortunately the OG white, Core Grafx and regular Duo are the most common revisions of the hardware.

Also, and lastly. I want to challenge the terminology being used to describe the artefact that I am seeing. So far as I understand jailbars are usually used to refer to very thin lines superimposed on an image. With the PC Engine the artefact appears as more of a couple of very thick columns. Reminds of that one single thick column in the middle of the screen that some SNES revisions have.

[RGB32E]

The only bearing it has is how well the RGB levels are amplified (video quality in general).

Correct, and that's all I was getting at.

Console lottery and display has more bearing on if you notice it or not.

...
Yes, that is what I am suggesting. I have modded a number of PCE units and built several amp designs and in my experience White PCE units display the least noticeable jailbars. Where as the TurboGrafx16 has some of the worse. Duo's in the middle. The Supergrafx tends to have some bad ones.

Have you kept any records that would help identify Hu6260 video quality? I don't recall if the Hu6260 had any revision codes or not printed on it, but that might be one way of tracking quality?

And? I see no correlation between the two.

There isn't a direct correlation between the two. But it is pretty awful.

He found that if you strap some extra capacitance between pins 41 and ground and pin 43 and ground on the 6260, the jailbars are greatly reduced. I have done this to several consoles and it indeed helps. Especially on Duos. Also, on Duo-R/RXs if you replace Cap C961 with something like a 220uf it also helps reduce it even further. On a TG16 replacing C142 helps.

I'm curious to replace TG16 C142 with a 220uF cap and see if that makes any improvement! I've given the equivalent of this a try on a TD, but I don't recall any gains in PQ for doing so.

I am 100% confident that no amp design by itself will eliminate jailbars. This is a problem that needs to be tackled at a system video level prior to any kind of amplification.

I don't believe I've ever claimed total elimination, just that some amp designs and implementations appear to make the issue less noticeable. The AV-DRIVER does the best job of any design I've found, and can get the right output levels without having to use an additional resistor divider circuit on the outputs like with the 6dB triple channel designs (e.g. THS7314 designs).

[Fudoh]

Also, and lastly. I want to challenge the terminology being used to describe the artefact that I am seeing. So far as I understand jailbars are usually used to refer to very thin lines superimposed on an image. With the PC Engine the artefact appears as more of a couple of very thick columns. Reminds of that one single thick column in the middle of the screen that some SNES revisions have.

absolutely right. But since the Raiden screens in the opening thread show the problem perfectly fine, it's safe to say that we all mean the same problem. "Classic" jail bars - as seen on a Mega Drive - are nowhere to be found on the PCE systems.

[alamone]

Just finished modding my OG white PCE... looks good so far,
any games (hu-card only) where the jailbars are most prominent?

[kamiboy]

Best game for seeing the intensity of the artefact for me is Dragon's Curse. The desert level. Look at the sky and it should be pretty visible if you have a problem or not.

Do report back, I am curious to know how the white model performs.

[incrediblehark]

I have found my white pc engine looks best in an rgb modded ifu-30. I dont think the jailbars are gone completely but are virtually unnoticable, especially when scrolling which is what usually bothers me with jailbars. My turbo duo not only has them, but the picture is slightly darker and I get some sort of other interference on screen that is essentially wavy lines and a fuzzier picture. its a shame because i would rather use my duo but the picture quality looks so good on the ifu-30 i use that instead. Both are using the same amp. I posted questions about it on pcefx a few years ago and tried thesteve's fix but it didnt seem to do anything for me.


Edit: Just wanted to add that is there a difference in picture quality when you pull rgb directly from the huc6260 compared to the pins on the expansion port? thats the only difference i can think of between my pc-e and duo mods.

[kamiboy]

Are you using an amp? The RGB quality from a Duo and standalone PC Engine should be the same. I believe the expansion pins are connected directly to the GPU pins. Also, there is a definite jailbar fix now, detailed in another thread here.

[leonk]

Look at the first post here: http://shmups.system11.org/viewtopic.php?f=6&t=56083

Link to fix for ALL systems that works perfectly.

[incrediblehark]

Yes both are using the same amp. Thanks for the link I'll check it out!