Hello all,
I'm trying to repair this motherboard which will not turn on. Initially I found a short on +5VALW the always on 5V rail and it turned out to be a shorted U8 which is a usb power supply. I replaced this part but despite the short being gone now, the rail does not turn on. I tried removing the part again and it makes no difference. When i force enable PU202 to turn on it will make +5VALW just fine but it squeals a bit. If i isolate this output the squeal goes away. It seems something draws too much current perhaps but there is no low resistance reading from this line to ground so if there is an issue, its going to be on a dependent IC and the issue is on it's output rather than on +5VALW it feeds from. I removed all power ICs directly dependent on +5VALW one at a time to see if this did anything but no result, the rail still wont power.
On the other hand +3V3ALW runs fine. The other rail that works is BATT++ whih is making 9V. All other rails are off. EC chip feels a little bit warm, is this normal?
Anyone have a clue what I could do? Is there maybe a reset procedure that I could try?
Schematic attached.
I'm trying to repair this motherboard which will not turn on. Initially I found a short on +5VALW the always on 5V rail and it turned out to be a shorted U8 which is a usb power supply. I replaced this part but despite the short being gone now, the rail does not turn on. I tried removing the part again and it makes no difference. When i force enable PU202 to turn on it will make +5VALW just fine but it squeals a bit. If i isolate this output the squeal goes away. It seems something draws too much current perhaps but there is no low resistance reading from this line to ground so if there is an issue, its going to be on a dependent IC and the issue is on it's output rather than on +5VALW it feeds from. I removed all power ICs directly dependent on +5VALW one at a time to see if this did anything but no result, the rail still wont power.
On the other hand +3V3ALW runs fine. The other rail that works is BATT++ whih is making 9V. All other rails are off. EC chip feels a little bit warm, is this normal?
Anyone have a clue what I could do? Is there maybe a reset procedure that I could try?
Schematic attached.
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