Sorry, I had a typo in the last post. I meant to say the power on signal on
pin 24.
The power switch signal on pin 20 is working properly... 5V when the button
is not pressed, nearly 0v when pressed.
On the bad board, I found that pin 14 of the COP is low when the system is
turned off, 0.5v. On the working board this pin is ~3v when the system is
off, 0.5v when the system is on, and 5v when the power state is changing
(powering on or off). This pin is supplied power by 1K resistor R46 form
the 5v standby rail, and is pulled low by pin 39 on the keyboard 6552 pin
39.
If I remove the 6552 the system powers up with the bad card! So getting
closer...
With the system plugged in both sides of R46 show 5v... suspicious. Sure
enough, the trace on the output side of R46 is broken. Fixing that will be
tomorrow's project.
-J
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Received on 2017-10-27 13:17:34
This archive was generated by hypermail 2.4.0 : 2020-01-13 12:15:17 EST