MY PC Wont Boot!

[8daysaweek]

PC Info
MotherBoard: GIGABYTE GA-Z87-HD3 (1.x)
On-board graphics
BIOS Ver: F8
CPU: Intel Core i5 4670K S1150 3.40 GHz
CPU Part No.: SR14A
Memory: Corsair CML16GX3M2A1600C10 / 2 x 8GB
Operating System: Win 10 64-bit
SP: 1?
Antec Power Supply: 500
HDD's: Samsung & Seagate

I have the following problem:

When I power-on my PC:
I don't hear the usual single POST bleep, and Windows does not open.
Instead, only the fans run, and I can hear a faint intermittent-click, like the click I hear when I press the reset-switch.
Eg: It sounds as if the PC keeps starting and then instantly resetting itself, eg, on/off, every 2/3 seconds

The monitor does not display anything, or even power-on.
The HDD does not appear to be on.

So next:
I shut the PC down.
Disconnected each of the following items,
one item at a time, and then re-booted,
but I've still got the same intermittent-on/off

First I disconnected the:
HDD, CMOS battery, DVD Drive,
The second of my two memory sticks (from slot 2):

Then I swapped over the memory-sticks, eg:
I replaced the memory-stick in slot-1 with the memory-stick that I'd previously removed from slot-2.

Next:
I unplugged my Network Cable & my monitors D-Plug:
And now the PC gives one bleep...
(like the single POST bleep I usually get at power-on, which would normally be closely followed with the display of the gigabyte logo, and the boot options along the bottom of the screen)

But as I've got the monitor disconnected, I cant see what is actually happening.

So I powered-down the PC, then I rebooted,
and now I'm back as before, with the same intermittent-on/off

Next:
I unplugged all remaining external connections, and removed my only PCIE card from its top slot.
But I've still got the same intermittent-on/off

Finally:
I removed the remaining memory-stick in slot-1.
Now I hear continuous rapid bleeps.
So I powered-down the PC, and...

I put the same memory-stick back into slot-1.
And got the same intermittent-on/off

So now:
I've disconnected all of the internal removable devices
and I've unplugged all external connections.
And I still get the same intermittent-on/off

I've checked the voltages on one of the power cables
that would normally plug into a HDD, which are:
Pink: 3 volts
Black: 0 volts
Red: 4.6 volts
Black: 0 volts
Yellow: 11 volts

NB: I connected the negative lead of my analogue meter to the PC case.
NB: Its a cheap meter so the voltages may be showing a bit low?

Q: So what's causing this, and how can I rectify it?

Q: What are the minimum items that need to be connected to the mobo, to allow the mobo to do the POST?

Thanks.

 

[Calvin7]

Voltages are beyond acceptable tolerance limits. You need to replace the power supply. You might want to check your warranty on it to see if you have a claim.

 

[8daysaweek]

Voltages are beyond acceptable tolerance limits. You need to replace the power supply. You might want to check your warranty on it to see if you have a claim.

I've now checked the voltages with my digital meter, so are these OK?

Pink: 3.32 volts
Black: 0 volts
Red: 5 volts
Black: 0 volts
Yellow: 12.12 volts

Many thanks

 

[shknawe]

Did you pull your gpu and try on board graphics? Oh never mind I see you only use on board graphics.

 

[shknawe]

Voltages are beyond acceptable tolerance limits. You need to replace the power supply. You might want to check your warranty on it to see if you have a claim.

I've now checked the voltages with my digital meter, so are these OK?

Pink: 3.32 volts
Black: 0 volts
Red: 5 volts
Black: 0 volts
Yellow: 12.12 volts

Many thanks

Yes these are normal ranges black and black are ground wires.

 

[shknawe]

I would venture to guess your motherboard has died. You have normal power going in, you have troubleshooted everything I would have advised to do.