I am trying to debug a soft power problem on a IIci... I would appreciate any ideas!
When I got the computer it wasn't turning on, but it worked with a PICO ATX supply bypassing the soft power, although had no sound.
I recapped the computer and now sound is working.
Now to the soft power... I am using a PSU replacement from TT design that uses a PICO ATX and has a soft power control circuit (with a transistor similar to what I have seen in the forums).
1) When the computer is off, I can turn it on with the keyboard or power switch. Everything seems to work....
2) However, if I turn the computer off via the menu or pressing the power switch it powers off at first, but then goes in an infinite loop where it repeatedly powers on for a moment and off again. I see the logic board LED light up, and the speaker briefly pops, then off, and again and again.
I am trying to debug this by looking at the Power On signal from the mac, while I turn the PSU rails on and off manually. With the computer on, pressing the Power button or shutdown from the menu causes the Power On signal to go down. The computer stays on at this point because the PSU is bypassing the Power On signal. But ... when I turn off the PSU (after the Power On signal is down) I see a bump in the Power On signal. I assume this is what causes the cycling when the Power On signal is controlling the PSU.
I am wondering if this bump in the Power On signal when the power rails go down is normal, or if there is a problem with my logic board. The bump is spread-out but gets sufficiently high that can trigger the PSU back on. I also notice that when the Power On signal is down its not all the way to zero. When the power rails go down, we see the bump and the signal goes to 0.
When I got the computer it wasn't turning on, but it worked with a PICO ATX supply bypassing the soft power, although had no sound.
I recapped the computer and now sound is working.
Now to the soft power... I am using a PSU replacement from TT design that uses a PICO ATX and has a soft power control circuit (with a transistor similar to what I have seen in the forums).
1) When the computer is off, I can turn it on with the keyboard or power switch. Everything seems to work....
2) However, if I turn the computer off via the menu or pressing the power switch it powers off at first, but then goes in an infinite loop where it repeatedly powers on for a moment and off again. I see the logic board LED light up, and the speaker briefly pops, then off, and again and again.
I am trying to debug this by looking at the Power On signal from the mac, while I turn the PSU rails on and off manually. With the computer on, pressing the Power button or shutdown from the menu causes the Power On signal to go down. The computer stays on at this point because the PSU is bypassing the Power On signal. But ... when I turn off the PSU (after the Power On signal is down) I see a bump in the Power On signal. I assume this is what causes the cycling when the Power On signal is controlling the PSU.
I am wondering if this bump in the Power On signal when the power rails go down is normal, or if there is a problem with my logic board. The bump is spread-out but gets sufficiently high that can trigger the PSU back on. I also notice that when the Power On signal is down its not all the way to zero. When the power rails go down, we see the bump and the signal goes to 0.
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