The laptop is an older Satellite A300 running a clean install of Windows 7. It turns off randomly, sometimes right after logon, sometimes after half an hour or more, but on average within the first 5 minutes.
So far I have come up with these facts:
The computer turns off suddenly like the power has failed. Nothing weird shows in Event Viewer
The computer doesn’t seem to turn off when in safe mode.
Swapped power brick with another with no luck
The fan works fine and neither the CPU or any other part overheats.
Took the battery off. It was dead anyway
There are no scorch marks and all connectors seem fine. I retouched the power connector solder joints just in case
I tried to bend and manually put pressure on various parts of the motherboard. It didn’t make it turn off.
I used freeze spray. Nothing happened
I removed the memory DIMMs and tried using only one every time. I also used the Windows Memory Test tool. No problems with memory
I don’t know what else to do. Any ideas?
I think it is heat related. Most of the older laptops I’ve worked on have sucked a mat of dust, link and animal fur in through the fan and have deposited it between the output of the fan and the radiator for the CPU and GPU. The fan may be spinning just fine, but are you feeling air coming out the radiator exhaust?
I’ve pulled 1/8th inch thick mats out of laptops of this vintage that were indistinguishable from felt.
I agree with JerrySTL’s thought to get a working battery. If you’re relying on AC power, and it drops for whatever reason, you’ll turn right off. Reflowing the solder at the power connector was a good idea, but it could be a bad solder joint somewhere else as well.
When I’ve had power problems, it’s always been the power cord near where it attaches to the laptop. The wires there get flexed a lot, and eventually can begin to have intermittent contact. I have this problem right now, and I have to manipulate my power cord until I see the battery is charging. If I had a dead battery, I’d have exactly the symptoms you have. I know you said you swapped the power brick, but I’ve had them fail this way three times now, so it’s still possible.
One way to test this would be to fiddle with the power cord near the laptop connection, to see if you can make it die on purpose. Another thought to try would be to hook the laptop up to an external keyboard and mouse, and use it as a desktop so that you don’t ever jostle it, to see if it tends to stay up longer.
I am 100% sure it is not due to overheating. Overheating was my first thought so the first thing I did was to clean the fan and heatsink fins and reapply thermal paste. Also, I am currently holding the bare motherboard in my hands and the heatsink is barely warm.
I found on a Toshiba forum that these A300 series laptops had some problem with CPU throttling and that caused these random shut downs.
This explains why the computer doesn’t turn off when in Safe Mode. It probably doesn’t use any power scheme and the CPU doesn’t shut down.
I wiggled the cords, bent the board and applied pressure here and there, just in case there was some connection fault but I couldn’t reproduce the problem.
It’s a fresh install of Windows 7. Have you installed all the updates from Toshiba’s web site, especially the Chip Set Utility? It’s possible a standard install of Windows 7 is disagreeing with Toshiba’s hardware.
You’ve done every diagnostic within reason., Likely culprit is simply a flaky IC or other electronic component that shorts randomly when powered up and heat levels rise in the material of the component. Short of MB replacement there’s no economical fix for these scenarios.
Any chance you can use a utility to look at the hard drive smart status like in speedfan. I have seen plenty of flaky drives cause this behavior and windows will not always capture the error.