old desktop wont start up - what to do?

So if I've understood it, and assuming that old and new PSUs are both rated to work with the old system:
The old PSU works with the new motherboard, so the old PSU seems OK.
The old motherboard doesn't start up with either old or new PSUs, so it points to the motherboard or something plugged into it like a graphics card.
The power switch is momentary action so if it starts things going with either PSU then it most likely OK.

My guess is that the old and new PSUs are seeing excess current being drawn and shutting down to protect themselves. The new PSU just takes a bit longer before it sees the high current as a fault (probably not unexpected if it's a higher wattage).

Do you have a graphics (or any other) card on the old motherboard that you could remove / swap to elimitate that being the cause?
 
wonko said:
Do you have a graphics (or any other) card on the old motherboard that you could remove / swap to elimitate that being the cause
Click to expand...
Atm nothing is plugged in but a cpu. I've taken everything out to see if that made a difference which it didn't.

What about the battery of the motherboard? Can this cause an issue? Given the pc has sat there for so long doing nothing. I have replaced it, but not like for like. In theory the 2 batteries are the same (just captivity and thickness is off, but I'd have thought the thickness wouldn't cause any problems.

I can't however confirm if the new battery I've put in has power, as it too has sat unused in a packet for a few years
 
Higher Than Average said:
Atm nothing is plugged in but a cpu. I've taken everything out to see if that made a difference which it didn't.

What about the battery of the motherboard? Can this cause an issue? Given the pc has sat there for so long doing nothing. I have replaced it, but not like for like. In theory the 2 batteries are the same (just captivity and thickness is off, but I'd have thought the thickness wouldn't cause any problems.

I can't however confirm if the new battery I've put in has power, as it too has sat unused in a packet for a few years
Click to expand...
It is still a bootable system though? I.e. RAM, CPU heatsink and fan, on-board graphics. If not then it's obviously not going to boot properly, but I'd expect some signs of life with maybe some error beeps.
I've seen some odd effects at boot-up with a low battery, but I'm not sure if a dead battery could stop a motherboard booting altogether. Have you not got a multimeter to check the battery voltage?
Also, have you tried resetting the CMOS memory since replacing the battery?
I'm guessing you put a CR2025 battery in instead of the usual CR2032? It's a fraction thinner so it's possible it's not making a good electrical contact, and TBH for the cost I'd stick a fresh CR2032 in to rule that out.
 
Higher Than Average said:
Nope.

Just ram, cpu, fan, it does exactly the same as before. Either nothing with the old psu, or a split second on off with the new psu.

Nope.

How?
Click to expand...
I don't see how you're going to narrow it down unless you've got a system that should be capable of booting (including onboard graphics if your mobo/CPU support it, otherwise a graphics card).
If you find your motherboard manual online it should say how to reset/clear the CMOS memory, it might be small button located near the battery. Removing the battery for 5 minutes or so normally clears it too.
 
assuming it is the motherboard, how would i know i've got one that'll work with my current components?

the board is

Gigabyte
GA-Z77-D3H

i assume the graphics card i have will likely work on most other motherboards, but i know the CPU is different on this to how i'd expect, with the pins on the board, not on the cpu, which I think is called LGA
 
Try powering off the PC then hold down the power on AND reset button for 10 seconds it will trigger the back up bios and it will reflash the original.
 
OK that's a fairly old board. I've just looked it up, and there is a jumper labelled "CMOS_CLEAR" next to the front panel connectors - if you short these two pins for a couple of seconds (with it powered off) it should clear the CMOS memory.

You're right that components have all moved on... that board uses an LGA1155 CPU socket and DDR3 memory, so you can't start swapping the CPU or any DDR4/5 memory from your new machine, even if you wanted to risk it. If the old PC didn't have a graphics card in it, then it would be using the integrated GPU in the CPU. If you can't get it booting with this on-board graphics then it's probably dead and there seems little point trying it with a graphics card.

There are quite a lot of 'not booting' posts on various forums for this board, and some seem to be down to a corrupted BIOS as mingey suggests above. Personally I'd go one step at a time and get it in a minimally bootable state first and try clearing the CMOS memory after putting a known good battery in it first. If it's not teaching grandmother to suck eggs, try as follows:
- CPU installed with heatsink fan plugged into the CPU_FAN header
- Both PSU ATX and ATX_12V connectors connected
- 1 stick of RAM (motherboard manual may advise which slot)
- case front panel power switch plugged in to the motherboard, plus ideally a case speaker so you can hear any status/error beeps (I'd connect the reset switch later just in case that was shorted)
- keyboard and monitor connected
- no graphics card (providing your CPU has an integrated GPU as above)
- no HDD connected

If there's no obvious life like the CPU fan spinning then it's probably toast, but if there's some life but you can't get as far as the BIOS screens then try the BIOS recovery process. There seem to be a couple of ways to do it if mingey's method doesn't work.
 
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