RGB PC Engine Jail Bars

[RetroFixes]

Ahhh Jailbars, this was and still is an issue with original Famicoms too. There were several different fixes for that console. I wonder if any would work for the PCE?
As I recall the methods involved were disconnecting the RF, grounded copper shielding under Graphics chip and 220uf Caps across the certain pins of graphics chip. There has never been a universal fix due to the insane amount of motherboard revisions. There might be info to use from their research.

[leonk]

I've modded a few Turbo systems now for RGB using the Ti 3 channel based amp. So far, I noticed:

- TurboGrafx-16 has jail bars
- Turbo Duo has them as well
- Original PC engine inside of RGB modded IFU-30 is super clean

[kamiboy]

By original do you mean the first release, the white one? Because that is consistent with my own findings. Though I still need to purchase a OG PC Engine to confirm.

[FBX]

Anyone check to see if this is some sort of video encoder interference like on the original Genesis consoles? You know, where you have to sever the trace leading from the VDP pin 50 to the CXA chip?

[kamiboy]

Hard to tell. Information about the PC Engine is so sparsely scattered around dozens of sites. There does not seem to be any communal effort, only individuals working things out in isolation.

[CkRtech]

only individuals working things out in isolation.

And sadly, it seems that many in the community would rather shoot down others' ideas rather than encourage them to try things and report results.

FBX - The PC Engine outputs the video signals from the GPU rather than use an external encoder - at least for native NTSC. PAL systems were a bit of a hack and did use an separate encoder.

I have no idea if people have truly experimented much with it, but I would say that it might be worth comparing results on your display by altering which sync signals you use. It seems like most people just use the cvideo sync that is already available. There is also a csync available (Pin 44) that some have tried straight/buffered. You even have horizontal and vertical sync available at both the CPU and GPU. Those could be combined and generate a csync signal independently from the GPU.

Despite the clock signal for the CXA1145 causing issues with the Genesis, I have read on a couple of other websites (non-gaming websites) that oftentimes sync signals are the ones to blame for visual artifacts including jailbars.

Regarding the PC Engine once again, I believe Artemio's solid color screens did not display any evidence of jailbars on jailbar-plagued PC Engines (at least for those that tried them. Check his 240p test suite thread), and that had me wondering if it is indeed related to sync.

[Strider77]

Jail bars are, forever.....

[FBX]

Jail bars are, forever.....

Not on the original Genesis as I mentioned. One little scrape of a trace on the motherboard, and I was free!

[kamiboy]

I've suspected the sync signal myself. Currently I think I am using composite video as sync. I believe that I at some point tried c-sync from the GPU, to no avail, though I need to confirm that. Next I would like to use C-sync from the GPU through a simple transistor amp circuit to see whether that helps.

But that stuff with H & V sync being available from the CPU sounds pretty exciting. Maybe avoiding the potentially noisy sync from the GPU and instead building ones own c-sync directly from the CPU source might be a solution.

Though I am not sure what sort of amp, and combining circuit, would be needed to achieve that.

[mikehaggar]

Has anybody here tried the following jailbar fix?

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

Some people say it totally solved their problem, some say it merely improved it but that they are still there, I'm not sure what to make of it.

[leonk]

I only saw jailbars on duo. I tried above fix and it didn't work. It just softens them but doesn't remove. Only white small PC engine is super clean for me.

[kamiboy]

I tried the above fix as well, and found that it did not remove the bars. From my limited understanding of electronics such capacitor fixes suggest that there is noise in the power source of the signal producer which results in noise in the signal.

[kamiboy]

Just got done doing an amped c-sync mod on my PC Engine Duo. I used the simple transistor mod using a C1815 and a bunch of different resistors.

"Jailbars" were still there. Now all that remains is to try a white OG PC Engine.

[mikehaggar]

this modder in this auction claims his method is "jailbar free"

http://www.ebay.com/itm/PC-Engine-Duo-C ... 1271420873

His pictures are very convincing....has anybody else tried this method?

[kamiboy]

Bulllllllllllll shiiiiiiiiiiiit. That is the same three channel TI7314 amp mod being used in one form or the other by several people here, myself among them.

Nice circuit diagram though, I've seen the thread that is from.

To be fair I am not using the exact same parts in my amp, so there is a faint possibility that his claims hold true. I cannot be arsed to build that exact version of that TI7314 amp though, so if some one else wants to step in be my guest.

[Pasky]

It can be jailbar free depending on the console really. IIRC it's the old whit pc-engines that have it really bad. My US duo and TG-16 doesn't have jailbars grabbing it straight from the Hu chip.

[kamiboy]

Actually my findings so far are that only the white PC Engine is jail bar free, every other revision of the hardware has it in one way or the other. They can be hard to spot though, so you might think your system is free of the artefact until you pop in that one game and reach that one spot which really highlights the fault.

[Pasky]

I'm pretty anal about video quality and a lot of people here will just test with their tv, I use my capture card (without running it through the xrgb) and my tv's. Capture cards seem to be a lot more susceptible to noise on the video signals than CRTS and some LCD's. I could see the jailbars via my PEXHDCAP on my Sega Genesis but couldn't see it on my CRT. Neither my TG-16 or my Duo have the jailbars when looking at it through various games and using the solid color backgrounds and patterns on the test rom either.

[Fudoh]

Actually my findings so far are that only the white PC Engine is jail bar free, every other revision of the hardware has it in one way or the other.

I have jail bars using my white PCE, but almost none using my Core Grafx II. Both running in the same RGB modded interface unit. Quite a mystery that little box....

[kamiboy]

Pasky, what amp are you using?

[Pasky]

NCS2553

[alamone]

I used to have a Duo-R (white) which I modded using the TI amp; it had noticeable jailbars.
I sold it, thinking that jailbars are just part of the system, but since I've seen reports here
from users saying that the OG white PCE is jailbar free I'm going to be modding a white one,
using the amp PCB sold by mickcris on our forum. I will be removing the RF box and installing
a 8 pin mini-DIN in place, and I plan to tap the RGB signals from the interface pins.
The loss of CD support isnt a big deal to me as I prefer the hucard games in general.

[kamiboy]

You can put the amp inside the IFU-30, the you wouldn't habe to lose CS games, nor would you need to mess with your PC Engine system, and you could pop different PC Engine hardware revisions in and test the performance of each.

If I had several PC Engine revisions that is what I would do.

[alamone]

Like I said, don't care about CD and not planning to have more than 1 PC engine so I think I'm going to mod it internally still.

[kamiboy]

NCS2553

Strange that you use that particular amp. None of the PC Engine specific amp circuits I've seen use that amp.

Maybe that makes the difference.

[Pasky]

NCS2553

Strange that you use that particular amp. None of the PC Engine specific amp circuits I've seen use that amp.

Maybe that makes the difference.

I doubt it, it's just a 6dB amp.

[broken]

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

Pro tip: it doesn't.

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


Thesteve has provided some remedies that greatly reduce jailbars.

[RGB32E]

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!

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?

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?

NCS2553

Strange that you use that particular amp. None of the PC Engine specific amp circuits I've seen use that amp.
Maybe that makes the difference.

I doubt it, it's just a 6dB amp.

The NCS2553 goes for about half the price of the THS7314 (50 cents vs $1). Guess that's why Gametechus decided to use the NCS2553 instead of the THS7314 in a couple of his projects (saved $10!!!). I somewhat kid though. The NCS2553 appears to have a slightly sharper LPF compared to the THS7314 if that makes any difference?

[RGB32E]

Jail bars are, forever.....

[CkRtech]

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

Why?