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Just put together first build. fans come on but mobo won't beep

Last response: in Systems
March 2, 2011 12:14:25 PM





monitor is 32" sony bravia lcd tv

my psu to mobo has a 20+4 pin connector and another 4 pin connector connected to an 8 pin mobo outlet. is this normal?

i have tried booting with no ram and no gfx card but still no beep so doesn't that mean problem is cpu, psu, or mobo? what can i do to test/fix?
a c 90 B Homebuilt system
a c 203 à CPUs
March 2, 2011 12:36:59 PM

rajohns08 said:
my psu to mobo has a 20+4 pin connector and another 4 pin connector connected to an 8 pin mobo outlet. is this normal?
That's not unusual and its certainly acceptable.
Related resources
March 2, 2011 1:09:27 PM

WR2 said:
Hello rajohns08;

Run through the forum's "System won't boot" checklist

yes i have done those things. i did notice however that the system speaker wire seems very loose compared to all the other wires plugged in to motherboard headers.
March 2, 2011 1:10:51 PM

and is the cpu power the extra 4 pin connector i was talking about that is plugged into the 8 pin mobo outlet?
a c 90 B Homebuilt system
a c 203 à CPUs
March 2, 2011 1:42:09 PM

It should look like this - and there should only be one way it can be plugged into the 8pin socket.

What happened when you bread-boarded the system?
March 2, 2011 2:12:49 PM

sorry, i stopped at the last numbered point. so i try to boot up with mobo outside of case? so i hook up psu to mobo and that's it?
March 2, 2011 2:16:48 PM

well im assuming i have to have cpu in also?
March 3, 2011 6:02:07 PM

local store told me i had bent pins on cpu. is it possible to bend pins back into place successfully?
a b B Homebuilt system
a b à CPUs
March 3, 2011 8:03:50 PM

rajohns08 said:
local store told me i had bent pins on cpu. is it possible to bend pins back into place successfully?

Yes. Take a mechanical pencil, slide it over the pin, and very gently bend the pin back.

However, a few bent pins shouldn't stop it from POSTing all together.

To breadboard, place the motherboard next to the case on a piece of cardboard. Connect the CPU/HSF, PSU, motherboard speaker, and power switch. Everything else can be disconnected for now. Make sure both PSU power connectors are plugged in. Try turning it on.
March 4, 2011 1:50:40 AM

gigaparts already had pins fixed when i got there. on computer now
a c 90 B Homebuilt system
a c 203 à CPUs
March 4, 2011 2:08:01 AM

Im sure that's a major relief for you.
Just out of curiosity -about how much did that run you?
That type of question will comes up a lot and we don't have many good answers.
Thanks for the update.
March 4, 2011 2:58:11 AM

they charged $35.00 for the diagnosis and didn't charge me any additional fee for fixing the bent pins. pretty sweet deal.
a b B Homebuilt system
a b à CPUs
March 4, 2011 3:16:59 AM

Honestly, that's not a bad deal. I figured it'd be much more.
a c 122 B Homebuilt system
a c 172 à CPUs
March 4, 2011 7:31:09 AM

rajohns08 said:
yes that is what it looked like and there was only one way to plug in. what is breadboarding the system?

Work systematically through our standard checklist and troubleshooting thread:
I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

If not, continue.
The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.

I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

Breadboard - that will help isolate any kind of case problem you might have.

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.

Make sure you plug the CPU power cable in. The system will not boot without it.

I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

If no beeps:
Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.

At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.

Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.

Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.

Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.