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NEC TG-16/TE/TurboDuo => TG/PCE Repair/Mod Discussion => Topic started by: ginoscope on September 23, 2016, 04:20:31 AM

Title: RGB mod question for sync
Post by: ginoscope on September 23, 2016, 04:20:31 AM

I had my PC Engine Duo modded for RGB before I became comfortable enough to handle most of these mods myself.  The guide and mod that was used on my duo was this one (http://www.otakus-store.net/en/content/6-guide-nec-rgb).

Sync on my duo is coming from pin 44 of the 6260 and the composite trace has been cutoff.  The RGB picture I get is very nice but I am now missing the composite image.  Question for people who have tried both is how much better is the pure sync RGB picture vs just using composite for sync?

Not that I care all that much about composite but it be nice to have an easy option to hook the duo to my CRT.

Title: Re: RGB mod question for sync
Post by: mickcris on September 23, 2016, 05:19:01 AM

The sync directly from the IC is not really supposed to be used like that.  People do it though and it does work, but you are supposed to put it through an amp circuit first.

I would say that composite video for sync with viletim's jailbar fix looks great.  I would just put it back to composite video and do that fix.
http://etim.net.au/av-driver/pcebars/

Title: Re: RGB mod question for sync
Post by: ginoscope on September 23, 2016, 05:41:56 AM

Thanks for your input mickcris I was thinking of reconnecting the composite and seeing how the picture looks.  It's an easy change in either direction and all other RGB guides leave the composite intact so was curious if there was any reason to leave mine this way.

Title: Re: RGB mod question for sync
Post by: Keith Courage on September 23, 2016, 07:43:57 AM

I've seen or heard of issues where sometimes using regular composite video backgrounds in solid colors for some games can look kind of grainy compared to using true sync like you have it hooked up now. however, this does not happen that much and basically depends on the system and or device you are hooking it up to. so if you put it back to composite and you don't see a difference then no need to go back. However, if you do see a small difference you could always add a small switch to the rear of the system so you can swap between the two.

In my experience with pc engine DUOs most do not require sync and work just fine with regular composite. Duo-Rs on the other hand usually require pure sync from the video chip.

Also when tapping sync directly make sure to use a 220uf or higher value capacitor in line to help hold a steady sync signal. + side to the chip and - side out to the Av jack.

Title: Re: RGB mod question for sync
Post by: ginoscope on September 23, 2016, 08:51:15 AM

Thanks for the input I may consider the switch route if I can find a small one since that would be best of both worlds.

Title: Re: RGB mod question for sync
Post by: Xenogears on September 26, 2016, 11:17:24 AM

Another way is, just using CVideo passed through an LM1881 IC, Sync Stripping all different signals out. If you use Pin 44 from the Video Chip, pass it through an amp. I