Two Dead Motherboards! Help!

[abrogard]

Had an Asrock z77 wouldn't switch on. 
Tested the PSU with a tester and it said all okay except -5V.

Went to an old Acer Aspire which was working well and took the PSU from it and tried it.  But it didn't work. 

So we decided to use the Acer and moved it into position.  And then it wouldn't work.

Tested both PSU's and both are all okay except for -5V.

Neither machine will switch on.

Both machines have an external power on switch from the jumpers on the motherboard in order to cut out the case switch as being the problem.

The Acer has been using that for switching on for a long time.  With no trouble.

Well now the Acer switches on the PSU and the CPU fan rotates. But the case fan doesn't turn and there's no life to the monitor at all, no POSAT, no nothing.

The Asrock does nothing.  PSU fan doesn't turn.  Case fan  no,  cpu fan, no.

Any ideas?

[camerongray]

Don't worry about the -5v - It's an ancient rail that modern PSUs don't have as nothing uses it.

You said that the Acer had issues after you "moved it into position" - Are you sure it's not something external to the computer such as any of your peripherals that you are connecting that are causing the problem?  I'd suggest disconnecting everything from the computer so you literally just have the power connected and then see what happens (may even be worth trying a different wall outlet just in case).

[abrogard]

 Wow, thanks for the speedy reply.  And thanks for the info about the -5V.  I've asked in so many forums and nobody answers that question.  It is like I didn't ask.  Very good to have it settled once and for all.

 The computers were one in the workshed and one in the boy's room.  Asrock in his room.  Acer in the shed.

 So I don't know of any peripherals in common that they've shared.

 The Acer PSU was exposed to the Asrock board and the Asrock PSU was exposed to the Acer board.  ie. I swapped them whilst trying to solve this.  Gave him mine and tried to use his on the Acer.

 Apart from that nothing in common I can think of.

How bare bones can I get and expect to see some response from the motherboard?  I've got them back to motherboard, HDD, keyboard and mouse and get the response I mentioned, which boils down to nil really.

Noticed the case fan of the Acer gives a twitch when I switch off the power   It never switched on but it twitches on the way off.

And the Acer sits there making little clicking sounds like a HDD seeking maybe,  while the screen is black and there's no other signs of life.  Eventually it switches itself off.

It is time I learned how to trouble shoot motherboards.  I have about maybe eight collected from past failures where I"ve taken them out and put in new (second hand usually) ones.

If I can get on top of a trouble shooting, diagnostic routine I could go through them and finally figure out what will work and what should be thrown away.

This hassle now might be a good time to get that together.

[jimbean]

this could blow up your pc so take advice with a grain of salt
ive had at least 3 different mobo`s and case`s and power button issue`s over the years what i have done is take a screwdriver or metal object and jumped the connectors that the power button wire attaches to on the mobo it worked for me and there was nothing wrong with the buttons and or mobo`s they worked for years after in my case

[patio]

You can safely ignore the above advice...

[abrogard]

 That advice is redundant in my case.  I did mention that both computers are currently fitted with and external power on switch from the jumpers.  That is effectively what the poster is talking about.  Only instead of shorting the jumpers I've put in a momentary switch to make things easier for myself. 

That eliminates the case switch as the cause of the problem. 

I already knew the Acer had a broken case switch.  It needs the new one.

The Asrock apparently doesn't because it made no difference.

And now it makes no difference to the Acer,  either.

They both have a problem somewhere else.

[Geek-9pm]

For what it is worth...
There was a 'recal'l on the Asrock z77 motherboard.

Asrock Intel Recall - ASRock In the News

Does not make any sense.  Issue seems to be SATA ports.
Does anybody here know more about this?

Relevant information:
http://www.asrock.com/mb/Intel/Z77%20Extreme4/

[BC_Programmer]

ASRock has over 16 different motherboard models using the z77 chipset. A more descriptive model number could be useful. I imagine it is safe to say that it's not one of the motherboards that feature a power switch and reset button directly on the motherboard or the Debug LED display, as I'm sure you would have noted both of those.

A minimal test for a motherboard would be with only the CPU installed. It should then give a Beep code indicating no RAM, which in this case should be three long beeps. If it doesn't, then it is either a failed CPU or a motherboard problem. as ASRock motherboards will do absolutely nothing (No beeps or anything) without a CPU or with a failed CPU. If it does, then you add back components and attempt to power it up until it fails- which would tend to point you at the last component you added.

It is safe to say there is no visible damage or obviously failed components such as capacitors on the motherboards?

It can also be useful to remove the motherboard from the case (assuming you haven't done so), mostly because it makes it more accessible but also because the issue could be caused by a short with metal components of the case.

One useful feature is the aforementioned "Diagnostic" LED. This is a two-digit, seven segment display that is mounted in many modern motherboards and the Hexadecimal code that it shows effectively tells you what the motherboard is doing. These are an integrated version of a diagnostic tool called a "Diagnostic POST Card", so even without one on the motherboard it is still a possibility. these are expansion cards that can be installed which will effectively monitor the startup process and display a Hex Code. If you have several motherboards that you think have failed it could be useful to get one of those to determine where things are going wrong as it may point you towards possible remedies, or at least give you "Closure" that the board is dead.

[abrogard]

  That's a good idea.  In fact if I go rummaging around I think I might have one of those - bought for pennies from eBay some time in the past on the spur of the moment and never actually used...  I'll go looking for it...

  Before I give them up for dead I'll do that ' reflowing ' thing.  It seems to have worked sometimes.

 With me its mainly nonsense.  The boards I have are mainly so old they're historic relics really.  Even my 'good' ones are now getting to be so old....

 But I amuse myself...