PC not powering up question

I have been asked to look at a mates PC that is failing to boot at all - no POST seen or anything. Checked all the connections and and those looked fine so bypassed the power switch to rule that out (still no boot) so then proceeded to check the power supply. Did the pin test and got no fan spinning up so ordered a new power supply as it looked to be where the issue lay. What I hadn't taken into consideration was that the Corsair CS550M has a Zero RPM mode so it won't spin the fan up at low loads. Figured that out after I replaced the power supply and nothing changed.

Currently I don't have access to a multimeter - a friend has borrowed mine and I can't get it till Tuesday to prove that we are getting the right voltages across the supply but I have done the short out test between the green and black wires on the power supply and I can hear a click like a relay engaging so it might be OK and also the chance of two power supplies not working is pretty slim I would imagine. In an effort to prove that the PSU is OK what I have done is have attach the PSU to a spare motherboard I have here and connected all the power switches and a speaker with a stick of RAM and a random heatsink fan to it to see if it will power that but nothing. Would this be because it has no CPU on the board? I would have thought that it would do something - if only make a series of beeps to show that there is no CPU. It is this that is confusing me more than anything at the minute - so if anyone has an answer it would be interesting to hear.

Also any suggestions as to what the issue might be? Once I have tested the PSU voltages and proved that they are OK then the next step will be disconnect as many peripherals as possible - HDD, graphics etc and see if that might make a difference but could it be motherboard issue? It is a Gigabyte GA-H110M-DS2 so a decent brand and not an obvious candidate for being the cause of the issues to my thinking but not sure what else would give the symptoms I have got.

Thanks

without a multimeter it becomes difficult. But you can start with checking if there are any bad capacitors on the motherboard.
It does not happen often but sometimes it does.

Since I do not know how good you are on electronics, I'll add a link so you can identify them.
Some basic information about capacitors and how to identify the bad ones

Try replacing your CMOS battery. I had a motherboard a few years ago which I thought was dead. I tested the CMOS battery and it appeared to be dead, so I replaced it, and the computer came back to life!

Sir you are a damned genius! POST, beeps and fans spin up! Will have to put it all back together later but thanks very much for that. A lesson learnt there...

Amazing what that one little battery (or the lack of it) will do.

It is indeed - I must admit to being a bit skeptical about it quickly followed by be rather bemused about it all. End result though is it is fixed and can be sent back to my mate which I am rather pleased about to say the least.

Thanks again.