PC unreliable till it warms up

A few months ago my PC started giving trouble, spontaneously rebooting in mid use. Then it began to die in mid-use, as if the power cord was pulled out of the wall. In this state it was completely dead to the reset button or even holding down the power switch. It had to be unplugged from the outlet and plugged back in again before it would reboot.

I leaped to the conclusion that the power supply was faulty and was all set to replace it when the problem went away. I should have replaced it anyway but I’m a lazy, lazy man.

Now it’s showing new symptoms - it locks up completely shortly after being switched on. This is independent of operating systems - it even locks up the BIOS screen. But if it is left locked up but with the power still on for about fifteen minutes, it reboots happily and works all day.

I still suspect it’s a power supply problem and I’m planning to replace it tomorrow, but if anyone knows better or has seen this sort of thing before I’d be grateful for any clues!

It could well be the power supply (or any of a number of components), since any component that has a damaged connection in it can connect better as the parts expand. Poorly done solder joints are notorious for this.

However, I’m leaning towards it more likely being a problem of component seating. Take out the CPU and memory and put them back in, and maybe do the same to any adapter cards in the system, and also maybe the power connector as well. It seems kinda silly to take something out and just put it back in the same place, but this insures that the component is seated properly and all the electronic bits are making good contact.

Modern PCs are turned on by a signal from the motherboard. Motherboard problems (particularly the CPU or memory not being seated well) can cause the power supply to not work properly, making you think the problem is somewhere other than where it is.

One other thought, after the PC has been running for a while, reboot and go into the BIOS and check the CPU temp. Is it above 50 deg C? If so you have a cooling problem (and may now have a CPU/motherboard problem as a result).

If you have a utility that will monitor the CPU temp from your OS then obviously you won’t need to reboot and go into the BIOS to check it.

Along with engineer_comp_geek’s great advice, while you have the side off…take a visual of the insde. No build up of dust anywhere? All capacitors have nice flat, shiny bottoms, not bulging or discoloured?

Already tried reseating adapter cards and CPU, didn’t check the memory for seating or pay any attention to capacitors. I’ll give those a shot!

I didn’t think of a dry or cracked soldered joint expanding. There is definitely a time delay before the lock-up - it always boots successfully, or I can get into the BIOS and fiddle around. Then a couple of minutes after power-up it locks up. Leave it on for ten minutes and restart and everything works as it should.

I’ll try reseating the memory, have a squint at capacitors and maybe borrow a power supply first to make sure.

When I get problems like that, I like to experiment with removing memory modules. I’ve found that bad RAM will cause problems like that. Of course that will be a little difficult if you have only one memory module.