IFU-30A - RGB Mod quality limited?

[Trenton_net]

Hey everyone,

When modifying an IFU-30A for RGB output, is there anything inherent about the hardware that would limit the quality of video being generated? I know the jail bar fix has to be applied to the actual PCE console itself, but would anything else cause an issue?

The reason I ask is because I have a PCE Core 2, modified with RGB out and jailbar fix and it looks flawless on my framemister. However, when that same console is placed inside an IFU-30A and I use the RGB out on that device (Which was modded by a different person), I get OK RGB out, but you can clearly see what looks like interference on the screen. On some areas of uniform color, you can see what looks like wavy line noise that kind of crawls up the screen. It isn't as pronounced as the jailbar issue, but its still interference that seems to occur in regular intervals.

Is that a product of a bad RGB mod? Or does the IFU-30A have some kind of hardware deficiency that limits the kind of quality it can output?

[wildfruit]

I had an RGB IFU that had wavy lines when there was a black loading screen. Didn't notice any other distortions. My current duo from KC seems to have no interference.

[CatPix]

Most RGB mods usually use the composite signal as the sync source - it's how SCART works.
However, this can cause interferences. The only way to prevent this is to use a LM1881 chip that pick up the sync signal from the composite signal and restiture a clean sync signal that should remove any interferences.

If you can have access on how the RGB mod was done on your console it could be interesting to know how it was made. It's possible that the RGB mod into your console pick up the sync signal before it get mixed with the video signal, ensuring the best quality possible. It's something that cannot be done on the IFU30 because the pure sync signal isn't present on the rear connector of the PC-Engine (unless I'm wrong). The limitation here isn't in the IFU-30 but into the signal provided to it.

[Duxcub]

Are you using an official NEC power adapter for the IFU? Every third party adapter I've tried has caused nasty horizontally scrolling lines on the screen. I package an AD-IF30A with all of my IFU RGB mods for this reason.

[mickcris]

The CoreGrafx was from me (i think) and is using the compsite video signal.  Its probably an issue with the other amp or the power supply as the amp should be connected to the IFU side in the same place as the console amp.

[Ergot_Cholera]

Could be a grounding issue, I have modded a few IFUs and found I got a little interference when I used certain ground points. Make sure the amp is powered directly from the the voltage regulator and the only thing coming from the PCE connector are the RGB signals.

[Trenton_net]

Thanks everyone. How likely do you think this is a power supply issue? The reason I ask is because it's the easiest thing to fix/replace. All the other fixes would involve me opening the unit and performing some modifications which I have no equipment/skill for.

[mickcris]

Fairly likely.  What supply are you currently using?

You could try your cg supply with one of these but it won't supply enough current to use the CD rom also.  Just to test if you have one laying around or want to do a cheap test. Can find them on ebay also
https://www.adafruit.com/products/2897?gclid=CLWK_tbJ080CFQxahgodnecLrA

[rxmage]

If you aren't using the NEC power supply, try a laptop style power supply.  I'm using a brand name one from a old NAS I had laying around (12V 3A).  I first tried some Amazon wall wart 12 2A supplies... pure crap that caused horrible video noise.

Good Luck

[L-Digital]

It's not necessarily a power issue. I had the same issue when I modded my ifu. I tried every method and could not get a clean picture. Especially on solid blues. In the end I modded the PCE itself and took the rgb from there even while in the ifu. This has given me a perfect rgb and gotten rid of the problem. I think I made a thread you can probably find for screens