DELL Optiplex SX280 pre-BIOS boot failure

10 Jul 2009
Posted by Laptop Junction

After 5 years of continuous operation in the machine, the ole DELL Optiplex GX110 is replaced by a 2nd hand DELL Optiplex SX280 SFF. This ultra small Pentium 4 desktop computer has the capability to operate on a 12 Volt car battery,  thus great for mobile use. Unfortunately, this SX280 lasted for just about an hour. It didn't restart after connecting a monitor and seemed doomed. Here's the story how the Optiplex SX280 was resurrected from the dead.

SX280 mobile capability

The DELL Optiplex SX280 Small Form Factor comes with an external power supply rated at 18 Amps @ 12 volt DC. That's about 250 Watt AC including power supply losses. With average processor load the SX280 consumes about 70-100 Watt AC, meaning it draws about 5 - 6 Amps DC on average from a 12 volt car battery.

Dell Optiplex SX280 SFF

SX280 Diagnostic indicators

At first the Optiplex SX280 passed a quick startup test and seemed very much OK. The backside showed 4 Green led indicators labeled by A, B, C and D. The front has a green lit power button. The startup sequence seemed normal too, just a quick buzz of the fan, after which BIOS started followed by a normal startup sequence.

DELL SX280 clock problems? Read about CMOS battery replacement.

Look here for the DELL SX280 Diagnostic LED indicators codes.
Look here for the DELL SX280 system light codes.
Look here for the DELL SX280 beep codes.

SX280 pre-BIOS boot failure

The Optiplex SX280 suddenly played dead after connecting a monitor while the power was on. Pressing the power button didn't shut the system down, the power supply cable had to be disconnected instead. Connecting the power supply cable again resulted in the following state:

  • The system starts directly with a AMBER lit power button.
  • Both fan's start after 2-3 seconds on full speed and stay at full speed.
  • The A,B, C and D diagnostic indicators at the back are off.
  • The system board LED is on and amber, indicating the state "standby". (AUX_LED)

Pressing the power button for 5 seconds turns the system off. The SX280 plays dead and can't be turned on again with the power button. Re-inserting the power cord results in the above state again.

Disconnecting SX280 system components

BIOS hasn't started yet, and it seems the (pre-BIOS) POST (Power-On-Self-Test) got stuck somewhere leaving the fan's at full speed. Assuming a failure somewhere in the POST procedure, the next step is disconnecting attached components such as memory, harddisk, keyboard, monitor and clock & CMOS battery. Sadly, nothing helped one bit, the SX280 played dead.

Next was the external 12 volt power supply. Behavior seemed ok, the power supply indicator turns from AMBER to GREEN when the SX280 started. The power supply wasn't particularly hot and didn't make any noise, power consumption was about 105 watt in this state.

Lifting the SX280 P4 processor - dust pile-up

As a last resort, the Pentium 4 was lifted from it's seat. First the cooling block was removed, pressing a plastic holding clip quite hard. The big aluminum block came of with out a problem. Quite a bit of dust was accumulated on 1 side of the processor. The front fan seems to blow dust underneath the cooling block, possibly reaching the first row of the Pentium 4 processor pins. The P4 was easily lifted after releasing the big clip holding it down in the processor socket. Some of the dust flocked into the processor socket when removing the big P4 chip. The whole area was cleaned properly with compressed air and the P4 was reseated and all other system components connected.

DELL SX280 dust accumulation near P4 under cooling block


SX280 startup after dust removal near P4 socket

Now first boot was successful, the POST procedure passed continuing with booting BIOS. Apparently the dust accumulated underneath the cooling block was the cause of stalling the POST procedure. Possibly transportation of the SX280 had reshuffled the dust underneath the cooling block and had reached the P4.

As a first confidence test, the QuickTest on the CD bootable diagnostic test CD available on the DELL website (ISO file) was executed and passed without a problem. Because of battery removal during problem diagnosis the SATA controller was disabled so no controller / harddisk was detected.

SX280 airflow and dust pile-up

The Optiplex SX280 is equipped with 2 powerful fan's on each side of the P4 socket / cooling block. The airflow runs from front to back and can be quite powerful when the fan's operate at full speed. This particular SX280 has no dust filter in the front fan opening, so can dust can easily be sucked in. Dust pile-up against one side of the processor, underneath the cooling block, is a result of cooling / airflow design. A simple dust filter and a 'dust' roof could prevent dust getting stuck near the processor.

SX280 dust pile-up underneath cooling block P4.

 After 2 months of operation

With 2 powerful CPU fan's, dust piles up rather quickly. The DELL SX280 SFF is located close to the floor.

DELL SX280 SFF fan opening with dust pile-up