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Old 07-11-2007, 12:55 AM
phe phe is offline
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Join Date: Dec 2006
Posts: 48
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Marty and Grant, here is what I see (with the CPU and memory cards removed):

With the system turned on, IC W pin 1 is HIGH; pin 3 is HIGH; pin 2 is LOW; pin 4 is LOW. These are observed with the switch in the middle position. Pushing the switch to protect gives no change to the above 4 pins. Pushing the switch to unprotect also gives no change to any of the four pins.

The way I read the diagram, these two pins should always be high and one of them should go low when the switch is pushed. Marty, this is opposite of what you said. One of us must be reading it wrong.

I removed IC W and ran some resistance checks (system off ).

Resistance between socket 1 and socket 3 = 0. Resistance across R13 = 500 ohms. Resistance across R14 = 500 ohms. I would expect this if the two resistors are in parallel. Does this confirm my suspicion that somehow the trace that runs from PROT to pin 3 is shorted with the trace that runs from UNPROT to pin 4? If so, I have absolutely no idea where that could be.

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