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NEC TG-16/TE/TurboDuo => TG/PCE Repair/Mod Discussion => Topic started by: Cucurbitacée on September 23, 2014, 06:48:35 AM

Title: Dead CoreGrafx, where to begin?
Post by: Cucurbitacée on September 23, 2014, 06:48:35 AM

Hello everyone,

I've registered here trying to find help with a now dead CoreGrafx. It was still working like 2 years ago when I put it in a shelf.

I took it out the other day to clean it up and to see how it was doing. But nothing, no signal at all on the TV. I've opened it in order to check what could be wrong.

And it's not good. I've plugged the power supply (not the original one, but still 9V 1A with the correct polarity) and tested a bit, I can read basically the base voltage between the ground of the power supply and almost all the point of the board.  :? Even with the power switch off.

So I'm guessing I have a massive shortcut somewhere, but I don't know where to begin. Could anyone tell me where to begin?

Thanks in advance.  :)

Title: Re: Dead CoreGrafx, where to begin?
Post by: thesteve on September 23, 2014, 07:39:15 AM

start at the 7805
center is ground, 1 in 3 out 5V

Title: Re: Dead CoreGrafx, where to begin?
Post by: Cucurbitacée on September 23, 2014, 07:50:11 AM

Thanks for the reply. So, the result is strange...

Between center and 1 = 0V
Between center and 3 = 0V

I've checked the fuse and the large diode (D102) and they are OK.

Title: Re: Dead CoreGrafx, where to begin?
Post by: thesteve on September 23, 2014, 05:56:26 PM

So your not getting any power into the unit

Title: Re: Dead CoreGrafx, where to begin?
Post by: thesteve on September 23, 2014, 05:58:19 PM

Using 7805 tab or center as ground check voltage at d102 and power jack

Title: Re: Dead CoreGrafx, where to begin?
Post by: Cucurbitacée on September 25, 2014, 07:16:35 AM

Hi,

So here is what I read:

Between 7805 center and D102 with power switch on:
0.3V

Between 7805 center and D102 with power switch on:
5V

And go 0V between the + of the power supply and 7805 center, in both position of the switch.

I'm still lost, thanks for your help. :o

Title: Re: Dead CoreGrafx, where to begin?
Post by: thesteve on September 25, 2014, 08:24:15 AM

the supply is + shell