Can anyone improve the rgb output on my duo?

[incrediblehark]

I just recently got a turbo duo, and had it region and rgb modded. everything works great, but for the rgb I'm getting the noticeable jailbars and some faint interference on the screen. I know there are some rgb amps that have been made that will essentially eliminate any of this for a near perfect picture. If anyone can provide this service or can build the amp please let me know!

[ogre]

Unfortunately as of yet I have not found anyway of eliminating the jailbars/lines. I have been researching many forums and no one has been able to solve this. I tried 3 different mods and they all produce these lines to varying degrees. All of these mods use the composite video to sync which if you look closely produces these lines as well. Maybe cleaning up composite or finding a way to use c-sync off the chip would help. The only suggestion I can make is to check all the grounds for the mod and the cable. If the ground is not solid it will intensify this issue and add interference.

[Samurai Ghost]

Sorry if this is slightly off topic, but are you saying that all RGB mods for DUO systems produce lines and interference? Can you post an example of what this looks like? Because I'm considering doing a mod to improve the video output of my DUO but might give up the RGB mod if it's inherently flawed...

[BlueBMW]

I dont recall having jailbar issues on the RGB modded systems I've used....  Most of them used composite for sync also.  They were typically based on the NJM2267 amp I believe.

Someday I'll get around to having these amps built...

only 1 1/2" square:

/RGBAmp_SyncFinal2.jpg

[ogre]

All of the mods I have tried have this problem. The one that has it the least is the one that uses the NJM chip for the amp. I have to see if I can find a picture that shows this better. Most games this is barely noticeable except when a solid light color is present in the backround. Games that have this the worst are all of Shinobi, all areas in China Warrior, alt level 2 in Dracula X, konami logo, some of the cutscenes in Y's, and some of the cutscenes in Double Dragon 2. The composite video has this issue too if you turn up the brightness you can kind of see it.

[thesteve]

my sega rgb mod has no jail bars, using a sony CXA encoder as the amp

im running sync on green not composite as sync

[DynamiteSJ]

I have one of these amps:
http://www.ultimarc.com/vidamp.html

Would that work out good for  TG16 rgb mod as an amp?

[thesteve]

thats an odd amp, as i havent heard of a display wanting over 1V of Vid
that amp converts vga to cab display

[DynamiteSJ]

its an arcade monitor amp.. bought it for my mame arcade machine but never used it since i ditched my arcade monitor and went for a LCD. Arcade monitor is just RGB seperately and sync. Seems like itd work right?

[thesteve]

yes it should work, it just may need 3 resistors added

[incrediblehark]

I'll try to post up some pics soon, I have two rgb pce/turbo systems, a us turbo duo with the jailbars, and a pc engine hooked up to an ifu30 thats been rgb modded. this one is a lot less noticeable, i think its there but the picture is a lot brighter so I don't see the interference or jailbars, which im fine wth. but i want to use the duo.

[grahf]

Hey Blue, would you mind sharing the resistor and capacitor values for that NJM2267 circuit? The original amp design is from here:  http://baku.homeunix.net/RGB/PCE_DuoRX/PCE_DuoRX.html  but it's not so clear to me exactly what values he's using. Plus he's using a transister based pre-amp/buffer, which some folks are leaving out. I already built one of the simplified versions of these amps, but the output was a bit weak. It sucks because all my equipment is still back in the US, so I can't really test the signals.

Here's the one I built:



I ended up replacing it with a simple transistor based amp for now. I just got one of those new XRGB-minis (the XRGB-3 replacement), which luckily likes the transistor amp just fine, but i'd like to finish the NJM amp eventually.

[grahf]

I'll try to post up some pics soon, I have two rgb pce/turbo systems, a us turbo duo with the jailbars, and a pc engine hooked up to an ifu30 thats been rgb modded. this one is a lot less noticeable, i think its there but the picture is a lot brighter so I don't see the interference or jailbars, which im fine wth. but i want to use the duo.

You probably already looked into this, but the interference issues could be as simple as using a noisy power source. Adding a nice sized cap between power and ground might sort it out, or you might try changing to a different power source.

[incrediblehark]

where exactly do I add the capacitor? I tried adding some from the amp to ground and amp to power but didn't work for me. but maybe i was doing it wrong. the power supply is the official duo ac adapter, whats a suitable replacement? I have a radioshack one but it wont power this thing like it does the ifu.

[thesteve]

you want the amp to use the +5 from the internal regulator.
add a 1uf ceramic and a 480uf from the +5 to ground as close to the amp chip as possible

[incrediblehark]

Thanks for the info thesteve, I don't think I have any spare 1uF so I'll take a trip out to Radioshack and hopefully give it a shot today.

[incrediblehark]

So I tried adding the caps as suggested and still no change, although I could have just done it comepletely wrong. I tried taking pics but didn't come out well. I also tried a different power supply but no change. In all honesty its not that noticeable except for solid colors and when the screen is moving. I think if I can figure out how to make the picture brighter like the pc engine it might look the same. In the end I'll probably have to have someone else take a look at it.

[HercTNT]

I have the same problem to, my rgb modded system also has jailbars.  steve, did you add your own encoder to your duo, or can you get rid of the jailbars by switching the rgb mod to green sync, instead of composite sync?

[thesteve]

my duo isnt modded, as i didnt have an amp setup handy.
one of me genny2's is and its running sync on green for direct connection to my monitor.

[HercTNT]

is it possible to resolder the internal wiring to put sync on green instead of composite?  I would be a matter of changing just one wire would it not? the jailbars can be pretty noticable depending on the game.

[thesteve]

it would take a couple parts to bring the sync up to ttl level and then a diode and cap to integrate it

[grahf]

And if that doesn't work out, you can also try using an LM1881 sync separator. They use a super simple circuit, and usually produce a rock solid, clean, sync signal.

[incrediblehark]

If its something I could easily solder to together then i could probably do it, otherwise I'm going to have to have someone look at the system for me.

[grahf]

If you can solder at all, it's super easy. If you get stuck, just ask.

[incrediblehark]

Thanks for all of the help everyone So what would I need to do with a sync separator? is this something I would build?

[thesteve]

yes its something to build.
you would use it to give true sync instead of composite to your monitor.
the "less bright" condition bugs me a bit. what amp are you using (chip, transistor, numbers)?

[incrediblehark]

Just opened it up and took a look. I had this installed by someone else (my other, better picture rgb system I had the same person build the amp but i did the rest of the work myself) The 2 chips read as follows:

2267D
JRC
7028B

[BlueBMW]

NJM2267, the same amps I had planned on using on my amp chip.  I've seen them used before with good success.  According to steve's calculations, it should be good if the surrounding components are done properly.

[incrediblehark]

And my pc engine rgb amp is the same, but for some reason the picture is brighter / jailbars virtually nonexistant on the pc engine. 

[thesteve]

look at wire routing (especially before the amp)
you could be getting crosstalk from the composite wire.

[incrediblehark]

I'm wondering if the difference is that in the Duo the rgb is tapped directly from the HuC6260 as opposed to from the expansion port on the PC Engine.

[thesteve]

that could make a huge difference

[ogre]

Do both systems have the 75 ohm resistor on output? Some modders may leave this out assuming you will put this in the scart/output cable.

[incrediblehark]

So I'm willing to accept that its the cause of tapping the HuC6260. I don't think there are any other points to get rgb from on the duo systems so I'm going to call it good. It still is a fantastic picture and hardly noticeable, I'm just very nit-picky I guess. Unless I try a sync separator as grahf mentioned (not sure how to build one) I'll stick with the PC Engine.

[thesteve]

without the resistor the pic will be too bright (if the chip needed one) but should not cause jailbars.

[thesteve]

solved


to solve jail-bar issue on rgb modded system replace capacitor C961 10uf with 100uf tant or 220uf aluminum.
the cap is from hu6260 pin43 to ground.
C142 on the TG16

[incrediblehark]

Wow! Thanks thesteve! I'll give it a shot later today, I didn't think this would ever really get resolved. I'll swap out that cap and post the results (hopefully) later.

[Shrapnoid]

I have a question that's sort of similar to this and what I'm about to suggest may sound extraordinarily dumb but, I don't have enough experience with electronics to calculate the outcome so, I usually just experiment with stuff and see wait to see what happens which I know is also dumb and unsafe but, I sometimes lack the patience to buckle down and study so, I'd like to know from someone who has an intimate knowledge of video connections/mods to tell me if they think that this idea might work. I'll just post a pic so, you can see what I'm getting at.

[thesteve]

simple answer........no (what was the point?)

[Shrapnoid]

simple answer........no (what was the point?)

Shoot! I sort of expected that. So, it wouldn't split the composite video into the three types of video needed to produce component video?

[thesteve]

nope

[BlueBMW]

If only it were that simple....   would save a lot of trouble

[Shrapnoid]

So, mmm... What *would* happen? Would it wreck something if I tried it anyway?

[thesteve]

wouldnt hurt a thing

[Shrapnoid]

wouldnt hurt a thing

Yeah? Well, that's great because I just loooooove to experiment!

[incrediblehark]

So I tried the cap swap and its very close, but not quite there yet. I attempted to take some pics and will upload them later

[thesteve]

ya could try adding a ceramic chip cap across the pins hu6260 pin43 to ground (pins 41 and 42) for additional filtering.
it was a major improvement right?

[incrediblehark]

It was only a marginal improvement, but still an improvement I believe. The jailbars are very close to being gone. Still gotta up the pics, hoping to get a chance tomorrow.

[ogre]

Holy crap does this actually work? 

[thesteve]

try it
im sure other caps failing would also cause picture noise, but that cap is just not big enough