PCE Turbo Duo RGB - No jailbars - working solution

[leonk]

Of all the RGB modded systems I've done over the past few years, none are as prone to vertical jailbars as the Turbo Duo / TG16.  I've tried many different RGB amps and they all exhibit the exact same output.  The jailbars are introduced into the video stream before the RGB amp.  I would like to thank thesteve from pcenginefx forum for figuring most of this stuff out.  He knows his obey stuff like no one else.  Thanks dude.

Now onto the guide.  There's actually multiple modifications you need to do to your Turbo Duo to get absolutely jailbar free RGB output.

1.  HU6260 modification



As per http://pcengine.freeforums.org/jailbar-fix-t233.html you will need to add 2 capacitors to pin 41/42 and pin 43.  (ignore the 3 wires - they're there for the RGB mod)

I used the following capacitors: http://www.digikey.com/product-search/en?keywords=1276-3300-1-ND - 22uF SMD ceramic capacitors.  Rated at 16V.

2.  C961 Capacitor

The original capacitor at this location is rated 10uF 16V.  Replace it with a 220uF 16V capacitor

Digikey link:  http://www.digikey.com/product-search/en?keywords=493-5357-1-ND

3. Better grounding on 8 pin DIN port



If you replaced the stock 5 pin DIN port with an 8 pin DIN port, you need to improve the grounding.  As is, the GND pin goes though a choke. You need to bypass the choke.  Because the ground is shared by all the other pins, the choke causes inverted crosstalk.

The results:  (please ignore the horizontal lines - it's hard to capture a good picture off a CRT / Sony PVM).

Before: (note the vertical jail bars in the sky)



After: (all clean!!)

[Keith Courage]

Just curious if you use regular composite for video or pure sync from the Hu6260 chip?

Also, are you using a TV that accepts a scart input or a device that converts it to a component or HDMI signal?

I've noticed that the severity of jail bars can sometime depend on the device being used to convert the signal.

[thesteve]

he said sony PVM

[Keith Courage]

he said sony PVM

My mistake. Accidentally skimmed past that part. Hard to see stuff sometimes on my phone.

[leonk]

That's correct, it a Sony 20" PVM.  I use an 8 pin DIN in place of the original 5 pin on the black Duo.  I wanted to make sure all original cables still work, so there is no CSYNC at the adapter, the PVM uses composite video sync.

The cable connects to a female SCART connector that goes to RCA audio + BNC R/G/B/Sync into the TV. 

Thesteve .. thanks for answering all my PM's!!

[wilykat]

Will it also improve composhit or S-Video as well?  Cheap mod to try anyhow and I do have 220uF cap sitting around. I need to get a couple tiny SMD caps though.

[mickcris]

thanks for documenting leonk.  Has anyone tried these other places that Otaku store has for larger caps?:
http://www.otakus-store.net/en/content/6-guide-nec-rgb

wondering if those help

[turbokon]

The two 22up caps usually fix the jail bars for me when component modding a duo.  The turbografx-16 is another story.  What's the equivalent cap to C961 for the tg16?

[Keith Courage]

I just wanted to post and say that I've done everything mentioned to remove the jail bars and it does not completely get rid of them for me. Especially in games like JJ and Jeff or Keith courage. slight jail bars and sort of a very minor checkerboard pattern can be seen in the background.

what takes care of it on my end along with all the modifications mentioned above is using pure sync off of the video chip instead of regular composite video for sync. Maybe it's the type of scart to HDMI converter I am using because I do not own a Sony pvm.

[SegaSonic91]

Is using pure sync for use on a CRT TV OK?  Or does it depend on the TV?  I was thinking of cutting the sync pin on the DIN8 and linking pin 44 to it rather than using the composite video.  I will also be doing what is suggested in the thread.  Jailbars are evil.  Now if I could get rid of that horrible "mesh" effect the PCE has, that would be even better!

P.S. I am drooling at the sight of Wataru in RGB on a PVM.  Damn those things are gorgeous!

[Keith Courage]

you can cut that trace and run pin 44 over to it as you said. however, in doing so you would no longer be able to use a regular AV cable for composite video in the future if you ever wanted to. if you want the option to use both pure sync or composite sync when wanted then simply install a switch to swap between the two.


Larger switch is a region switch. Smaller switch on the right is for composite/pure sync switch.

Using pure sync may not be needed depending on your setup. As for me it is needed with the scart to HDMI converter I use. Otherwise jailbars/checkerboard pattern is displayed.

[Ergot_Cholera]

Do you use SYNC straight from pin 44 to the din socket? I thought it needed amplification?
I get the mesh effect when I use comp video for sync on an original PC Engine, but not on the other consoles that have comp video (din 5) output as standard.
The jailbars seem worse on the din 5 consoles than the original PC Engine though.

[deubeul]

thanks for documenting leonk.  Has anyone tried these other places that Otaku store has for larger caps?:
http://www.otakus-store.net/en/content/6-guide-nec-rgb

wondering if those help

Today I replaced the C103 cap for a 1000uf one in :

- a non-modded Core1.
- a RGB modded Core1.

I hooked them to an RGB modified IFU plugged to a Sony CRT TV via scart cable. I had a significant reduction of the jailbars with both.

Then I tested the 2 syncs with RGB Core alone, RGB Core+IFU, and non-RGB Core with IFU.
Game tested: Wataru/Keith Courage.

- Using Csync, jailbars are almost totally unnoticeable, if not totally, but the very first deep blue screen just before the light blue title screen is a little blurish.

- Using composite video, that first deep blue screen is perfect but they're still some very light jailbars noticeable in the first level, but very heavily reduced. The image is a little less sharper when scrolling than when using Csync too.

I got the same results with the RGB Core alone and both Cores hooked to the IFU. So as this deep blue screen is the only one I got among the games I tested so far, I let the IFU wired with Csync.

Does anyone have an idea about that blurred screen?
 

[Keith Courage]

Do you use SYNC straight from pin 44 to the din socket? I thought it needed amplification?
I get the mesh effect when I use comp video for sync on an original PC Engine, but not on the other consoles that have comp video (din 5) output as standard.
The jailbars seem worse on the din 5 consoles than the original PC Engine though.

no amplification needed. Basically you cut the trace for the composite signal at the a/v jack and tap pin 44 from the video chip to it instead. or wire up a switch you can change between the two.

[leonk]

As KC already mentioned, CSYNC vs Composite Video sync very much depends on your display device.  Luckily, PVMs can sync on CSYNC, composite video, luma and even sync on green! 

I was wondering, if someone uses composite video sync SCART cables with a sync stripper in the SCART end, will it show the same result as real CSYNC?  If so, the sync switch will not be needed!