Member Avatar for Josie99

I am working on a Dell gx280 mini tower. I don't know the exact details of the 'power loss' but apparently the fan started making a noise like a 'hair dryer' and then the computer would not stay running. Eventually the computer would not start at all - another person tried putting a new motherboard in the unit and that appeared dead when it arrived - he couldn't get it going again so he returned it to the owner - that's when I got involved. I have had experience with around 150 of these models (in my job) and I found that the power supplies were lousy - probably had to replace about half of the power supplies because they 'died' in the manner described above so I got a new power supply and voila nothing happens - still no power but the aux power light on the motherboard. Any ideas of what to do next?

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  • Latest Post Latest Post by bobdowding07

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— given the fan noise, the system failing to stay on, and that a replacement PSU left only the auxiliary power LED lit, focus on narrow, measurable checks before replacing more parts. 's bench-testing idea is the right direction; the steps below add concrete meter checks and safe next actions you can apply right now.

  1. Safety first: unplug mains and ground yourself before touching components.
  2. Verify PSU standby and control signals (PS-ON and PWR_OK) with a multimeter: with the unit plugged in (but powered off) check the standby voltage (should be ~5V on the standby wire). To test the supply alone, short the PSU’s PS‑ON wire to any ground to force it on and then measure the main rails (+3.3V, +5V, +12V). If the PSU produces correct rails by itself, it’s probably fine.
  3. If the PSU dies only when connected to the motherboard, test the board with a minimal parts setup (CPU, one stick RAM, onboard video, speaker). Listen for beep codes or watch front-panel LED patterns. If the supply is fine off‑board but trips on connection, the motherboard is likely presenting a short or failing regulator.
  4. With PSU unplugged, check the motherboard for obvious physical faults (scorching, cracked solder joints, blown components) and measure resistance between power rails and ground — a near short indicates a failed onboard component. Do not probe live mains circuits; use the resistance check with power removed.

If rails are absent even with PS‑ON forced, try another known-good supply or a simple PSU tester. If the board shows a short or no POST after the minimal test, replacement or board-level repair is the remaining path; weigh repair cost against replacing the system and consider salvaging the drive if data recovery is needed. Follow ’s bench approach and consider ’s note about model-specific failures when deciding whether to repair or replace.

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Member Avatar for willcomp

The components which must be operable for a PC to power on are the PSU, motherboard, and CPU. It will usually power on with a faulty CPU unless electrical continuity through the CPU is lost. Barring a catastropic CPU failure, motherboard and PSU are left.

I recommend removing motherboard (with CPU and memory left installed) and testing on benchtop. Place mobo on cardboard or shipping foam, connect PSU and start using a jumper to short power switch pins.

Try using jumper to start PC before removing mobo from case to test for a faulty power switch.

Member Avatar for Josie99

I am assuming that the PSU is the Power Supply Unit? Thanks for answering - we will try these suggestions.

Member Avatar for willcomp

You assume correctly :-)

Member Avatar for bobdowding07

There is an issue with the GX 270 and 280 motherboards.They have capacitor issues.They bulge and rupture. If you didn't get it replaced by Dell by the Jan 31st 2008 deadline you are stuck.There is a website called Badcaps.com that sells the kit to replace the caps.Just Google GX 270 and there is page after page on it.

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