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NEC TG-16/TE/TurboDuo => TG/PCE Repair/Mod Discussion => Topic started by: bdoi on September 01, 2023, 04:37:33 AM

Title: GT black and white display issue
Post by: bdoi on September 01, 2023, 04:37:33 AM
I juste recapped a GT with a clean MB. but colors and brightness was washed. So I tried a LCDDRV screen and the display is just in black & white.
Any thought? a bad HuC6280? I thought to test a composite mod to see if there are any change
Title: Re: GT black and white display issue
Post by: Keith Courage on September 01, 2023, 10:15:11 AM
I recently worked on an express with a similar issue. Green is messed up with both an original screen and the LCDDRV. I tried tracing the green signal from the hu6260 chip but couldn't figure out why it wasn't displaying correctly. Maybe the hu6260 chip is faulty?

So I did a composite mod which looked normal and turned it into S-video by separating the Luma signal from composite. Looks pretty good on the LCDDRV.
Title: Re: GT black and white display issue
Post by: MasterofBiscuits on September 01, 2023, 01:14:55 PM
The LCDDRV boards have really poor quality control, I had one that was B&W and it turned out to be a bad connection on one of the pots that controls brightness/ contrast etc. I would recommend going over all the joints on the LCDDRV board with a soldering iron just to make sure.
Title: Re: GT black and white display issue
Post by: bdoi on September 02, 2023, 03:41:33 AM
The LCDDRV boards have really poor quality control, I had one that was B&W and it turned out to be a bad connection on one of the pots that controls brightness/ contrast etc. I would recommend going over all the joints on the LCDDRV board with a soldering iron just to make sure.

Yes may be some LCDDRVboard have some issue but there is an issue before the LCDDRV board so i don't think the issue comes from it this time
Title: Re: GT black and white display issue
Post by: bdoi on September 02, 2023, 03:43:27 AM
So I did a composite mod which looked normal and turned it into S-video by separating the Luma signal from composite. Looks pretty good on the LCDDRV.

Thanks, so you maje the composite mode and after modify it to make rgb mode?
Title: Re: GT black and white display issue
Post by: MasterofBiscuits on September 02, 2023, 01:16:07 PM
The LCDDRV boards have really poor quality control, I had one that was B&W and it turned out to be a bad connection on one of the pots that controls brightness/ contrast etc. I would recommend going over all the joints on the LCDDRV board with a soldering iron just to make sure.

Yes may be some LCDDRVboard have some issue but there is an issue before the LCDDRV board so i don't think the issue comes from it this time

Could be, but for 5 mins work I would recommend doing it. If you have a spare original screen, I would also try testing with that so you can try and isolate where the problem is coming from.
Title: Re: GT black and white display issue
Post by: bdoi on September 02, 2023, 01:56:52 PM
Yes i have tested 2 different stock screen and same issue so the issue came from the mother board not from the screen itself
Title: Re: GT black and white display issue
Post by: Keith Courage on September 08, 2023, 07:26:35 PM
So I did a composite mod which looked normal and turned it into S-video by separating the Luma signal from composite. Looks pretty good on the LCDDRV.

Thanks, so you maje the composite mode and after modify it to make rgb mode?

I didn't mod for RGB. The LCDDRV screen can also use composite or S-video. So I did the composite mod to the Express and then disconnected the Luma signal from the composite signal, amped the Luma signal using the traditional transistor method, and wired up S-video to the LCDDRV screen. Looks and works great.