Issues booting a laptop - general laptops, not just GRiD

[Caleb H]

So I've got this weird issue with a GRiD 1660 equivalent; when I got it for repair, it wouldn't boot at all, and after I replaced all the capacitors, it will boot once, but if the internal battery and capacitors have any charge, it will fail to boot again. It gets stuck in a sort of semi-on state where it thinks its on, so it refuses to turn on. I have a video of what it's doing:

And I have the service manual with a full schematic:

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Anyone have any idea where to start looking? I've stared at the capacitors, and they all look like the right value and soldered correctly, but I'd still guess that the cause of this issue might be either something I did while replacing the caps, or something that happened after the internal battery leaked on the lower main board, which I cleaned off with vinegar as best I could, but there could be some damage to something in the area.

 

[Istarian]

Maybe it has something to do with the soft-power circuitry or initializing the video controller?

The video footage makes it look like pressing the power button when it's on puts the system into a kind of 'sleep mode' which it then fails to wake up from without a hard reset/power cycling.

 

[Caleb H]

My guess was the soft power circuitry, but I'm not sure where exactly it is. For the video controller, wouldn't the fact that I can unplug it and then plug it back in, and the power light immediately turns on, suggest that it's having trouble turning off, not trouble turning on? I don't have a battery but I think it's reasonable to guess that if it had one, then the power light would never turn off. Maybe I could track down what turns the power light on and go backwards from there.

 

[Istarian]

Completely cutting the power, which is what likely happens if you unplug this unit and it has no battery attached, should effectively result in losing the contents of memory and the processor registers/state.

So when you plug it back and press the power button you would expect a cold boot.

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Part of the difficulty here is knowing how the soft power circuitry works.

My assumption (last post) is that pressing the power button while the system is on results in a sleep/suspend if there is power available (AC only, Battery only, or AC+Battery).

If that's true, you would expect to be able to wake it back up with the power button or keyboard activity.

Maybe that doesn't function properly without a battery installed? In which case it might not be able to wake itself up because the memory contents have been lost. And it wouldn't necessarily reinitialize the hardware.

In that "stuck" state does holding the power button down for 5-10 seconds result in a complete power down?

 

[Caleb H]

Completely cutting the power, which is what likely happens if you unplug this unit and it has no battery attached, should effectively result in losing the contents of memory and the processor registers/state.

So when you plug it back and press the power button you would expect a cold boot.

-----

Part of the difficulty here is knowing how the soft power circuitry works.

My assumption (last post) is that pressing the power button while the system is on results in a sleep/suspend if there is power available (AC only, Battery only, or AC+Battery).

If that's true, you would expect to be able to wake it back up with the power button or keyboard activity.

Maybe that doesn't function properly without a battery installed? In which case it might not be able to wake itself up because the memory contents have been lost. And it wouldn't necessarily reinitialize the hardware.

In that "stuck" state does holding the power button down for 5-10 seconds result in a complete power down?

I highly doubt it needs to have a battery installed, mainly because I remember having one of these laptops years ago that functioned completely as you would expect, and it didn't have a battery. I tried holding the power button down for about 10 seconds, but no change, it still didn't turn off completely or gain the ability to turn back on. The system it has for turning on is actually pretty complex, probably as you said so that it can support suspending:

Maybe the issue is related to IC31 or IC33, the VCC reset circuit?

 

[Caleb H]

troubleshooting step:


Also, there's no change with the LCD removed, it still acts the same. Also, the rest button does the same thing as holding down the power button, it just does it instantly rather than needing to be held down for about 1 second.

 

[Caleb H]

schematic of the power control circuit

 

[Istarian]

That does seem pretty complex and a failed diode, transistor (BJT or MOSFET) somewhere might cause weird behavior, but I don't know if they are testable in-circuit.

Does pressing the reset switch (SW1) behave as expected? It appears that there is a signal called SUSPENDON that is connected to thaat switch somehow.

 

[Caleb H]

That does seem pretty complex and a failed diode, transistor (BJT or MOSFET) somewhere might cause weird behavior, but I don't know if they are testable in-circuit.

Does pressing the reset switch (SW1) behave as expected? It appears that there is a signal called SUSPENDON that is connected to thaat switch somehow.

No, pressing the reset switch has the same effect as holding down the power switch. AKA, pressing the reset switch immediately puts it in this "purgatory" state.

 

[Istarian]

Hmm.

Well that switch appears to affect the signal output labeled /VDDRST (Vdd Reset, active low?).

On the other diagram, VDDRST appears to come from it's own reset circuit and is associated with IC 31 (DARH5VA45AAR).

Seems like the line would normally be held high by the voltage regulator off to the left and the switch would pull the signal level down to ground. Presumably that should initiate a hardware reset, but the systems is not being brought back up afterwards...

Do you have any documentation describing that bit or where the signal goes off to?