Troubleshooting a New Build

I have seen quite a few "new build failure" threads here. The following is one of my replies that I have cleaned up, expanded, and added to Tom’s Wiki. This assumes that the new build is completely dead. Even if not completely dead, the same troubleshooting principles still apply.

I have long been a proponent of breadboarding a new build. That enables me to test all of the parts before I install them inside the case. Breadboarding means assembling the components outside the PC case on an insulated surface. In the old days, say 10 or 20 BC (Before Computers), that literally meant using a wooden breadboard. I use a fairly thick nylon cutting board. ________________________________________________________________________
This is a general purpose reply. Comments specifically applying to my eVGA 122-CK-NF68 motherboard (Phoenix-Award BIOS) are in italics.

ed. Apr. 1, 2008 - I am currently assembling a system using a Gigabyte EP35-DS3P motherboard. The BIOS beep patterns for memory failure and missing video are the same.

Assuming the speaker is properly connected (or built in) to the motherboard, no beep means the POST (Powerup Self Test) did not start. A video card or memory problem that does not short the PSU out will still generate a beep pattern indicating video or memory problems. eVGA 680i board has builtin piezo beeper - doesn't need speaker. You should become familiar with the POST codes. Your motherboard manual may list them. If not, google something like "<motherboard model number> POST codes". The one standard POST code among the BIOS brands seems to the one short beep indicating that the POST was successful.

Check the back of the power supply. If the PSU has a 115/230 volt switch, make sure it is set to the proper voltage. If you plug a PSU set to 230 volts into a 110 volt outlet, nothing much will happen. The system simply will not work. The opposite is not true. If you are lucky, you will fry just the PSU.

Turn off the computer with the switch on the back of the PSU or unplug it. I prefer to use the switch if present. That way, everything is still grounded through the power cord. Wait a few minutes. While you are waiting, double check all the cable connections. Make sure that the case switches and LED's are connected correctly. Pay close attention to the main power and 4/8 pin 12 volt connectors to the motherboard. If the computer is completely dead, the case power switch may be bad. Swap it with the reset switch to test. Turn on the computer. If it still doesn't work, you have to resort to serious troubleshooting. eVGA 680i motherboard has builtin POWER and RESET switches - very useful for testing or troubleshooting.

If so, six possibilities:
1. The motherboard is improperly installed in the case, shorting something out. This happens surprisingly often. Verify that the metal standoffs in the case exactly match the motherboard mounting holes. Many cases have extra holes to fit different sizes of motherboards.

2. Bad or inadequate PSU. A working PSU will send a control signal called "PSGood" or something similar to the motherboard. eVGA calls it "PWROK". You can find this signal on pin 8 (gray wire) of the 24 pin power connector. It should rise to around 3.5 to 5 volts in less than 1 second after pressing the power switch. The motherboard needs this signal before the CPU can start the boot process. A problem with any output should kill the PSGood signal. Losing the PSGood signal forces a CPU reset. This is one of the causes of random resets because of PSU problems. Even with all of the power outputs present, if “PSGood” is missing during initial powerup, the CPU will stay reset. PC's with modern components NEED a good stable PSU. The +12 volt outputs are particularly critical. The forums here contain guides on how to select (by brand and capacity) a good PSU. And even a reputable PSU may be DOA or have other internal problems.

"Quick and dirty" under load PSU voltage checks (carefully, carefully) of the main outputs with
DMM black lead grounded and red lead inserted into the back of the various PSU connector pins
plugged into the motherboard:
yellow, yellow/black, and yellow/blue wires: +12 v
red: +5 volt
orange: +3.3 volts
blue: -12 volts
purple: +5 volt aux or standby - should be present if PSU plugged in and main power switch on
All readings should be +- 5%.

The 5 volt Standby or AUX output is completely separate from the main outputs. So seeing the red or green LED on the motherboard does not mean that the PSU is good.

While we are talking about PSU's, if you have a suspected bad PSU, also check the grey wire on
pin 8. It provides a control signal called "PwrOK" that the CPU needs to start booting.
With the PC off, it should be at 0 volts. It should go to around 5 volts (anything over 3.6 volts
will be OK) within .5 seconds after pressing the power switch. You can have all the power outputs
present. But if you don't have this, your PSU is broke and your PC won't boot.

3. A bad drive or video card that shorts out the PSU.

4. Bad memory.

5. Bad CPU.

6. Bad motherboard.

CAUTION - you need to remove power (ON-OFF switch on back of PSU or unplug it) from the computer each time you install or remove anything. I know this sounds stupid, but you'd be surprised ...

Disassemble everything.

Here is where I start any new build.

While the CPU is removed, inspect the LGA775 socket for obvious damage such as bent pins and debris inside the socket. (One poster at THG reported finding a tiny piece of wire that had fallen inside the socket.) Breadboard only the PSU, motherboard and speaker, and CPU and HSF. Doublecheck HSF installation, especially on an LGA775 board if using the Intel-style push pin mounting scheme. An improperly installed HSF will lead to thermal problems that should shut the system down within about 10 - 15 seconds (about long enough to complete the POST and start booting). If the problem was in the CPU socketing (very rare, but has happened), reinstalling the CPU should solve it. Plug in the main power connector and the 4 or 8 pin EPS connector into the motherboard. Now you need a way to turn on the computer. I normally use wiring, switches, LED's, and a speaker scavenged from an old case.


Turn on the computer. If the fans start spinning, you at least have some 12 volt power present. Look for any motherboard LED's. If you hear beeps, the computer at least started POSTing and the PSU, motherboard, and CPU are probably good. No beeps means that at least one of the three are bad. At this point, all you can do is test the parts by substitution. I say "probably good" here because an inadequate PSU could pass this test and fail later when it is more heavily loaded.

A working motherboard with only power connected and the CPU and HSF installed will complete the POST with a failure beep pattern. Beeps now should indicate memory problems. With no memory installed, an eVGA 680i mobo will generate a series of long single beeps. Install the memory. No beeps probably means that you have a shorted memory chip. Dual channel motherboards can operate with only a single memory module installed. Install each one separately and test. Sometimes motherboards do not properly set the memory operating voltage. That is a more complex problem than the simple "It won't start" problem. ("Simple" is not the same as "easy".) For one thing, if the computer does not start and complete the POST you cannot get into the BIOS to adjust the memory voltage.

With the memory installed, multiple beeps should indicate that the POST detected video problems. With no video card installed, a 680i will generate a series of one long and three short beeps. Install the video card, plug in any necessary aux power cables, and plug in the monitor. Turn on the computer. No beeps now means that the video card is shorting out the PSU. Otherwise, at this point you should see something on the monitor if the video card is good. At this point, if there are no problems, an eVGA 680i mobo will successfully POST (a single short beep) and the LED display will show "7F". The monitor will indicate a boot failure.

Turn off the PSU and plug in a keyboard and mouse. Turn on the computer. Try to enter the BIOS to set date and time and verify the amount of memory present. If you can do this, it means that all the expensive parts are probably good.

Start plugging in the rest of the components one at a time and test. No beep, and you have found the problem. If everything works, it probably means that something was improperly installed in the case. Reassemble in the case and test, following the steps above. If you are lucky, everything works.

I always breadboard a new build. I pretty much reserve the fourth port of my KVM switch for system testing.

John S. Casteel - "jsc" in the forums

More pages