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NEC PC Engine/TurboGrafx-16 Games/Consoles => Console Repair/Mod Center => Topic started by: Keith Courage on 09/04/2012, 05:38 AM

Title: DUO Problem
Post by: Keith Courage on 09/04/2012, 05:38 AM
Here is one I've never come across before. Hu cards work just fine. CD games freeze to a white screen when loading and CD bios screen is jacked up. Anyone have a clue what chip and or area might be the culprit? I know that bad traces or solder joints could be the problem. I'd just like a general idea of where to begin looking.

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Title: Re: DUO Problem
Post by: thesteve on 09/04/2012, 10:22 AM
bad workram
just had same issue on cd dock
Title: Re: DUO Problem
Post by: Keith Courage on 09/04/2012, 01:46 PM
IC106 is the workram in a DUO correct?
Title: Re: DUO Problem
Post by: thesteve on 09/04/2012, 09:51 PM
i believe so
Title: Re: DUO Problem
Post by: Keith Courage on 09/04/2012, 11:15 PM
Hmm I just changed out IC106 and it has the same problem still. What is the IC model number?
Title: Re: DUO Problem
Post by: thesteve on 09/04/2012, 11:27 PM
not sure
use a logic probe and check the data and addressing lines
Title: Re: DUO Problem
Post by: thesteve on 09/07/2012, 01:48 PM
it may be ic906, not sure
Title: Re: DUO Problem
Post by: Keith Courage on 09/07/2012, 06:31 PM
I found the problem. Did the push on top of the IC test and found the one that was causing the issue. Just needed to re-solder the pins to the board.
Title: Re: DUO Problem
Post by: thesteve on 09/07/2012, 07:28 PM
do tell
Title: Re: DUO Problem
Post by: Keith Courage on 09/07/2012, 08:31 PM
It was the NEC D78C14GF  R28 IC. I went around the board putting a bit of pressure on each IC while turning the system on and off and then checking the CD Bios screen. Putting pressure on this chip made it work so I then resoldered all the pins around it since I didn't know exactly which pin was not making the connection.
Title: Re: DUO Problem
Post by: Drakon on 09/08/2012, 06:53 AM
That's a funny fault.  I'm guessing most of the time it's just a loose connection somewhere.
Title: Re: DUO Problem
Post by: thesteve on 09/08/2012, 11:05 AM
that is funny, cause my parts board doesnt have a 7814 or equiv chip on it, uses all 3 digit part tags and uses the R tag for resistors.
they used the IC tag for chips
Title: Re: DUO Problem
Post by: Keith Courage on 10/08/2012, 04:27 AM
Well, I thought I had this DUO fixed. Worked fine for about a month and now having the same exact issue again. CD games will not load and CD bios screen is all jacked up. Anyone know which IC is the workram? I have been randomly swapping ICs from another DUO I have on hand because I don't know which one is the problem.
Title: Re: DUO Problem
Post by: thesteve on 10/08/2012, 02:22 PM
its either IC106 or IC906
106 is CD work ram
906 is system work ram

i think you have a solder joint or trace crack
Title: Re: DUO Problem
Post by: esteban on 10/08/2012, 02:48 PM
(https://junk.tg-16.com/images/sol.jpg)
Title: Re: DUO Problem
Post by: Keith Courage on 10/08/2012, 09:14 PM
Thanks Steve. I'll check it out. I am betting on a bad trace as well since I got the thing to work originally by pressing here and there across the board.
Title: Re: DUO Problem
Post by: thesteve on 10/08/2012, 09:32 PM
a cracked trace at the card slot is common
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