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NEC TG-16/TE/TurboDuo => TG/PCE Repair/Mod Discussion => Topic started by: HoocasLenkels on August 04, 2015, 01:39:54 PM

Title: TG16 with distorted graphics
Post by: HoocasLenkels on August 04, 2015, 01:39:54 PM

hello all.

I'm working on a TG16, and keep getting strange graphical issues. Here's an example.

(http://i58.tinypic.com/287eplz.jpg)

I'm pulling composite off the rf modulator pin. Same result when I pull from the expansion bus.

I've tried cleaning the cart slot, but no luck. Any ideas?

Thanks all!

Title: Re: TG16 with distorted graphics
Post by: wilykat on August 04, 2015, 06:06:03 PM

Service manual is your friend: http://gamesx.com/wiki/lib/exe/fetch.php?media=schematics:turbografx-16_unit_service_manual_-_smtg16.pdf

First, check all the caps, any of them burst or leaking?  If so, clean the mess and replace them.

The picture does not show anything in green, is there any other color beside red/pink/blue?  If not, something may be fouling up signal from HuC6260 to the composite pin and RF modulator.  Also I noticed there's jagged edges like some pixel color weren't correctly set.

There's schematic in the service manual, you could use it to check for pin to pin connection to find if there's broken trace or something.

Worse case: HuC6260 may need to be replaced.

Title: Re: TG16 with distorted graphics
Post by: thesteve on August 04, 2015, 07:42:35 PM

look at your video bus

Title: Re: TG16 with distorted graphics
Post by: HoocasLenkels on August 05, 2015, 05:06:02 AM

Quote from: thesteve on August 04, 2015, 07:42:35 PM

look at your video bus

Going from the 6270 to the two SRAM chips? I checked last night, but I may have missed something. I'll go over it again more thoroughly after work.

Thanks for the help guys.

Title: Re: TG16 with distorted graphics
Post by: thesteve on August 05, 2015, 04:18:42 PM

for missing colors your looking at the data between the 6260 and 6270

Title: Re: TG16 with distorted graphics
Post by: wilykat on August 06, 2015, 08:41:56 AM

That makes sense, video data has issue. What I'd do is print out the schematic from the service manual, print out just the one page with 6270 IC. Then with a good multimeter, set it to low ohm range, and check the trace between 2 pins from 6270 and both of the ram chip. Good trace should be at 0 ohms.  If it's high or infinity, it could be bad.