Member Avatar for fdhbyfh

After a small thunderstorm my PC wont power up, there are no lights either on the power button or on the back. I have tried to reset the power supply, tried a different power cord, different power source. the PC is in another state, so I cant physically see it. I suspect the power supply is bad, but I need help.

  • 5 Contributors
  • 5 Replies
  • 204 Views
  • 1 Year Discussion Span
  • Latest Post Latest Post by novarod

Dani AI

Generated

Concise, practical diagnostic checklist for a Dimension 2400 that is completely dead after a storm — complements ’s multimeter suggestion and ’s real-world notes about older supplies.

  1. Basic sanity checks first: confirm the wall outlet and the PSU rear power switch are live (try a lamp), and remove any surge strip between the PC and mains.
  2. Verify the PSU standby rail (purple wire on the ATX connector). With the PSU plugged in and the rear switch on the purple lead should read ~+5.0V. If that is missing, the board will show no LEDs and the system will not respond.
  3. If 5VSB is present, force the supply on and read the main rails: short the green PS_ON to any black ground (or momentarily short the two power pins on the front-panel header) and measure the outputs. Expected ranges: +12V ≈ 11.4–12.6V, +5V ≈ 4.75–5.25V, +3.3V ≈ 3.135–3.465V. On older systems a white lead for -5V may exist; if present it should be close to -5V.
  4. If the PSU will not start or rails are out of tolerance, test with a known-good PSU or a dedicated PSU tester. When bench-testing a supply outside the case, provide a small load (a case fan or a resistor) — some supplies need a minimum load to regulate correctly. Never open the PSU (dangerous capacitors).
  5. If the PSU tests good but there is still no motherboard activity or no standby LED, inspect the motherboard for blown or bulging capacitors, scorch marks, or damaged connectors; these are strong signs the board suffered surge damage. Given @novarod’s experience, a failed negative rail in an older PSU can cascade to the motherboard, so replace the PSU first and only replace the motherboard if a known-good PSU still produces no life.

Safety: disconnect mains before probing internal connectors, use insulated probes, and get a local helper to follow the checklist and report voltages or photos if the machine is remote.

Recommended Answers

All 5 Replies

Member Avatar for mike_d

How did you try the things you mention if it's in another state? Best way is open case and check power with volt meter at main harness from power supply. Pretty sure you can get a wiring diagrahm at dell.com for which leads should have what voltage. eBay has plenty of these power supply units for under fifty bucks. Simple to swap. Good luck.

Member Avatar for novarod

This thread is a little old but I can add some of what I've seen with these specific PC's. I have worked on three in the past year with the exact same symptoms (Thunderstorm, won't power up). I found in each case the -5v in the power supply was shot and the motherboard was defective. Those were the only two parts(power supply, motherboard) I've had to replace. I suspect the -5v was the reason the motherboard died as this type of failure will kill the mb.

Member Avatar for bama.mal

Open the case(side Panel) and see if there is a green light on the motherboard....I have one of these and have had a similiar problem....if green light is not on with the comp plugged in then the most likely cause is a deffective power supply....Mal....

Member Avatar for edna.cutright

Same problem with a Dimension 3000. I tried replacing the power supply, no effect, so I put the old one back. My next step was to buy a mobo ($69 ebay or $97 dell) and swap that.
You mentioned bad 5V will kill the mobo? How do I know the 5V is OK? I do get a green LED on the mobo.

Member Avatar for novarod

I have a power supply tester. It showed the power supply -5v as defective and that the power supply could possibly destroy the motherboard. The green light was on for each instance so that didn't help me.

I found my new motherboard on ebay for around $76 shipped. I have since installed a new power supply and motherboard, powered up tested, and all is well. This is the third one I've worked on and it failed exactly the same way each time (I service a lot of PC's).

Do yourself a favor, just go get a new power supply (cheap at www.newegg.com) and motherboard (ebay) and you'll be singing sweet songs before you know it.

Hope that helps.
novarod

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.