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NEC TG-16/TE/TurboDuo => TG/PCE Repair/Mod Discussion => Topic started by: fagin on March 08, 2014, 10:18:17 AM

Title: Corrupt graphics on Core Grafx II
Post by: fagin on March 08, 2014, 10:18:17 AM

Just fired up my Core GFX II today and appear to have corrupt graphics.  Opened the unit up and can't see any obvious trace issues and I reflowed the solder on the RAM chips.

Any advice or guidance?

Title: Re: Corrupt graphics on Core Grafx II
Post by: turbokon on March 09, 2014, 07:45:40 AM

Did you tried cleaning the hucard slot?


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Title: Re: Corrupt graphics on Core Grafx II
Post by: fagin on March 09, 2014, 11:37:23 AM

Graphics are corrupt even with a Super CDROM2 game.  If I swap the engine out with another, everything is fine.

Flashing pixels and vertical lines are quite commonly related to RAM issues afaik, which are the problems I have.

Title: Re: Corrupt graphics on Core Grafx II
Post by: pulstar on March 10, 2014, 12:55:59 AM

Do you have an oscilloscope or a logic probe? You'll be able to see if the RAM is at fault quite easily with either of these.

Title: Re: Corrupt graphics on Core Grafx II
Post by: fagin on March 10, 2014, 08:43:31 AM

I only have a multimeter I'm afraid.

Title: Re: Corrupt graphics on Core Grafx II
Post by: pulstar on March 10, 2014, 09:01:23 AM

If you're based in the UK I could take a look for you or you could just replace the RAM if you can find suitable replacements.

Title: Re: Corrupt graphics on Core Grafx II
Post by: fagin on March 10, 2014, 09:11:48 AM

Thanks for the offer (yes I'm in the UK), however I suspect once I'd sent it and paid for return back and your time, I'd be better off buying my own logic tester.  TBH getting hold of replacement RAM chips is probably not that easy either.

Title: Re: Corrupt graphics on Core Grafx II
Post by: pulstar on March 10, 2014, 09:25:36 AM

That's the problem with some of these old consoles, sometimes you have to have a faulty unit to take bits off of. Have you tried looking for the RAM online yet?

Title: Re: Corrupt graphics on Core Grafx II
Post by: fagin on March 10, 2014, 10:01:41 AM

Ahh good point.  I have a more or less knackered TG so I could use that as a donor if needed.

Nothing of use being returned on-line against those chip references unfortunately.

Title: Re: Corrupt graphics on Core Grafx II
Post by: pulstar on March 10, 2014, 11:18:24 AM

Looks like a donor jobbie to ressurrect the great obey :D

Title: Re: Corrupt graphics on Core Grafx II
Post by: Fidde_se on March 11, 2014, 12:45:27 PM

Sometimes when one of the voltage regulators start to give up, yes it's unusual, but it can start to show missing fragments in the graphics (parts of digital static in color), never seen it take over the picture totally but partly, starting when the regulator goes under 4.6V, it could be worth a check.

And while many circuits can run lower then 5v, not much but a little, big parts of it can still be operable, ram circuits usually don't tend to like it.

middle leg ground, the other is in and the other is out, and out should always be 5V (+/- 0.1v max).
(7805)

Title: Re: Corrupt graphics on Core Grafx II
Post by: fagin on March 13, 2014, 10:36:58 AM

I grabbed my nuts and took a RAM chip off of a TE and replaced one of the RAM chips on the CGII.  By luck it was the faulty RAM chip and normal service has been resumed.

 :D

Title: Re: Corrupt graphics on Core Grafx II
Post by: pulstar on March 13, 2014, 11:35:37 AM

Glad you got it working :D

Title: Re: Corrupt graphics on Core Grafx II
Post by: fagin on March 13, 2014, 09:50:17 PM

Quote from: nullity on March 13, 2014, 10:47:43 AM

What of the poor TE, though? ) :

It has a mainboard problem that I couldn't resolve...... so it's now relegated to a spares unit.  :wink: