RE: Stuck output(s) on G80 X/Y Cards / CPU no LED.

CPU will take clocking from the XY boards IF the crystal oscillator on the
XY boards is functioning AND plugged into the card cage - that's really all
there is to the clocking circuit to the CPU in G80 systems.

I find it most helpful to solder-tack a set of test leads to various points
on a board that are then terminated to a barrier strip, and then insert the
board into the cage. You can then scope/test them as needed.

Thanks,

Chris Brooks

713-341-9850

From: owner-vectorlist@vectorlist.org
[mailto:owner-vectorlist@vectorlist.org] On Behalf Of Arcadius Stempak
Sent: Tuesday, January 17, 2012 8:47 AM
To: vectorlist@vectorlist.org
Subject: Re: VECTOR: Stuck output(s) on G80 X/Y Cards / CPU no LED.

Anyone have any ' good ' methods for troubleshooting SEGA G80 CPU

and / or - X/Y Timing / Control - Cards?

I also wonder if I may have a Watchdog issue on the CPU Board itself?

But if the X/Y Cards provide clocking to the CPU Board and if these are

not functioning correctly, then I suspect the CPU may never come up.

Again appreciate any ideas that anyone can offer.

Thanks,

Sent: Tuesday, January 10, 2012 9:59 PM
Subject: VECTOR: Stuck output(s) on G80 X/Y Cards / CPU no LED.

>I have three sets of Sega G80 X/Y Timing and Control Cards.

>All three sets of the ' Timing ' Cards remain stuck a constant voltage

>output in the range of 1.50 to 1.66 VDC. Also the ' Control ' Card output

>remains at 0.16 to 0.22 VDC on all three ' R G B ' ouputs. I suspect that

>this may be the reason that my CPU card will not come up, and the CPU's

>LED remains off. I have replaced the crystal, on the CPU card, Z80 CPU

>along with memory (2114) on both the X/Y and CPU Cards. I also replaced

>the LED, itself. So far I get no output and the CPU seems to be non
functional.

>As a sidenote, I am using an Original Sega G80 power supply / transformer.

>All voltages(including the Reset power on voltage) measure as ' Good ' .

>Appreciate any ideas that anyone can offer.

>Thanks,

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Received on Tue Jan 17 16:14:10 2012