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NEC TG-16/TE/TurboDuo => TG/PCE Repair/Mod Discussion => Topic started by: Keith Courage on September 03, 2012, 10:38:05 PM

Title: DUO Problem
Post by: Keith Courage on September 03, 2012, 10:38:05 PM

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.

(http://img829.imageshack.us/img829/108/cimg6815k.html) (http://imageshack.us/photo/my-images/829/cimg6815k.jpg/)

Title: Re: DUO Problem
Post by: thesteve on September 04, 2012, 03:22:04 AM

bad workram
just had same issue on cd dock

Title: Re: DUO Problem
Post by: Keith Courage on September 04, 2012, 06:46:06 AM

IC106 is the workram in a DUO correct?

Title: Re: DUO Problem
Post by: thesteve on September 04, 2012, 02:51:05 PM

i believe so

Title: Re: DUO Problem
Post by: Keith Courage on September 04, 2012, 04:15:24 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 September 04, 2012, 04:27:00 PM

not sure
use a logic probe and check the data and addressing lines

Title: Re: DUO Problem
Post by: thesteve on September 07, 2012, 06:48:26 AM

it may be ic906, not sure

Title: Re: DUO Problem
Post by: Keith Courage on September 07, 2012, 11:31:25 AM

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 September 07, 2012, 12:28:31 PM

do tell

Title: Re: DUO Problem
Post by: Keith Courage on September 07, 2012, 01:31:15 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 September 07, 2012, 11:53:48 PM

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 September 08, 2012, 04:05:57 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 October 07, 2012, 09:27:28 PM

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 October 08, 2012, 07:22:14 AM

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 October 08, 2012, 07:48:05 AM

(http://junk.tg-16.com/images/sol.html)

Title: Re: DUO Problem
Post by: Keith Courage on October 08, 2012, 02:14:41 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 October 08, 2012, 02:32:49 PM

a cracked trace at the card slot is common