Member Avatar for kian.popat

Hi,
A few years ago my Power Supply for my Emachines 270 went bang and smoke came out. After searching many forums I had decided that we needed a new Power Supply. Yesterday, I got one with the correct specs for the computer and attempted to install it. I have triple checked that all the wires are in the right place and I am adamant it is installed properly. When I plugged it in and turned it on, the computer didn't start. There were no lights, or fan's on anywhere.

Is there a fault with the new PSU or has the past Power Supply damaged the motherboard too? And is there a way I can find out where the fault lies?

Please answer quickly so I can determine whether to refund it or not before my returns time runs out

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  • Latest Post Latest Post by johhny-marshal

Dani AI

Generated

Brief, practical diagnosis that goes beyond the usual “check the switch / reseat parts” suggestions from and . Given a prior PSU failure, the goal is to isolate the replacement PSU quickly (returns window) and then determine whether the motherboard suffered collateral damage.

  1. Visual check first: inspect the motherboard and PSU for scorched components, blown/bulging capacitors, or burn marks around the VRM/CPU area. Visible damage increases the chance the board is fried.
  2. Quick bench test of the PSU (isolates PSU from the system): with the unit unplugged, prepare a short between PS_ON (green) and any ground (black) on the main ATX plug using an insulated jumper or a commercial PSU tester; plug AC in and switch on. A working PSU should show 5V SB on the purple wire before the short and should spin its fan when PS_ON is pulled low.
  3. Measure rails with a multimeter or tester if available: approximate acceptable ranges are +12V ±5% (≈11.4–12.6V), +5V ±5% (≈4.75–5.25V), +3.3V ±5% (≈3.135–3.465V). If the PSU fails these or never powers up during the bench test, return it.
  4. If the PSU bench-test passes, try a minimal motherboard POST on the bench (CPU, cooler, single RAM stick, power connectors only). Bypass the case power button by shorting the front-panel PWR pins to rule out a faulty switch. No LEDs/beeps at that point points strongly to motherboard failure.
  5. If unfamiliar with mains work or voltage checks, use a cheap PSU tester or borrow a known-good PSU and swap briefly — swapping parts is the reliable, practical method echoed by @JorgeM.

Cautions: do not open the PSU (dangerous capacitors), avoid metal tools inside the case, unplug mains before moving wiring, and document the test results/photos for a return. If the bench tests show the new PSU is healthy but the board stays dead, the most cost-effective next step is motherboard replacement or professional diagnostic.

Recommended Answers

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Member Avatar for kian.popat

The Power Supply is a bit small for the case, I don't think it makes a difference but in case it does, there you go

Member Avatar for JorgeM

Yes it is possible that your motherboard is damaged. There is no specific information that can be provided to you to make that determination. When it comes to hardware repair, it usually diagnosed by swapping out parts. With the cost of the components, I am not aware of anyone that spends the time and uses tools these days to find the actual cause of the fault and repair the actual components themselves.

Member Avatar for 3knur8

Please dont take this the wrong way... but on the back of the power supply, there should be a switch with a "0" and "1" on it... make sure the switch is in the "1" position. New power supplies almost always come in the "0" position. Double check that before you decide it's the motherboard or any other parts.
When you turn the switch on, regardless if your motherboard is fried or not, you should at least have lights on your optical drive, and you may be able to hear the hard drive(s) spinning up.

Member Avatar for caperjack

A few years ago my Power Supply for my Emachines 270 went bang and smoke came out.

giving the time I would remove any addin cards and the memory clean connection and replace ,and as stated above maker the psu's on off switch is on .

Member Avatar for johhny-marshal

Well..kian, it might happen that motherboard got damaged with the power supply. You need to checkup and then try seitching on with the PSU

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