78lmt-usb3 wont post, no beep

[jonnydeen]

hi all,
having problems with a build.

specs...
78lmt-usb3 motherboard
phenom 555 be cpu with amd fx8320 cooler
1x 8gb ddr3 ram
generic 500w psu
asus gt610 2gb

symptoms...
when power is applied fans start but no visual output (onboard or gt610) and no beeps

i tried without the graphics card with no avail
tried moving the ram to a different slot

i also tried removing the ram and applying power to to check the case speaker was working, which it is

any help would be very much appreciated

[mikeyb5753]

do you have different ram / cpu to test?

[jonnydeen]

unfortunately not, although im trying to see if i can get my hands on some
im really befuddled as to why it there is no beep. i believe there should be one before boot but seeing as i have none im wondering could that narrow it down at all?

[autotech]

If you have bios F3 installed then i would try a different PSU. A generic 500 watt PSU probably only carries 15 watts on the 12 volt rail and you need more than that to power that CPU and graphics card. And saying it is 15 watts on the 12 volt rail is being opptimistic.

[jonnydeen]

wow just had a look at the power supply
the specs on the psu state

-12V 0.5A MAX !!

is it just me or is this thing only capable of 6watts?

what would i need to get things going?

[jonnydeen]

but thats only the -12v rail, i would have thought the +12v rails were used
the 12v+ rails are rated 14A and 15A
i dont see why this could be problematic

[autotech]

If it is dual rail and rated at 14a and 15 a the max per rail is what they are listing. No you can not join them to say it is rated at 29a the max would be 15 amps but with 2 rails that would be 7.5 per rail.  That is the main reason to buy a single rail PSU so you dont have to worry about the ups and downs. A single rail at 25 amps would make a world of difference.  It is the +12v rail you need to look at.

A PSU guru could give you the exact ratings of a dual rail but usually it is something like i mentioned it might actually carry 10a on one and 7 ot 8 on the other max.  Max means the maximum it can carry for a short period of time continuious watts is what you need to look at not max. 

Any 25 amp single rail will work at least 20 amps continuious with no problems.

[jonnydeen]

ah that make sense... so its just a split single rail
i got my hands on a corsair vs350 but unfortunately its still not sorted 
i think i can now rule out the psu