Luke Mawdesley
Member
Last Activity: 04-22-2025, 02:49 PM
Joined: 02-15-2024
Location: Baldwin, MD
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I just hooked up the PSU to the mobo and manually turned on power. The front fan spins up but no other signs of life from the power button or LEDs. Is this a mobo issue? -
Well unfortunately no. While both of these are 790s, one is 2nd gen intel and the other is 3rd gen. I noticed that some parts like the heat sync were slightly different but the PSUs look the same and are probably even interchangeable. When I opened the other one though it was completely different with an entirely different board layout....Leave a comment:
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I will do more testing later on this one later. I also took apart the other optiplex and found that it does have standby power, so I tried shorting the ground and PSON pins and it started up like normal with all power rails working. So I'm assuming the problem is with the mobo or power switch sending that signal....Leave a comment:
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Here are some pics. There is no printing as far as I can see. Also there was power on both sides of the resistors and caps so not sure what that means....
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There was no power anywhere near the chip, however I found the issue somewhere else. I was looking more closely at where the voltage stopped and saw that 2 small capacitors similar to these had blown out and were cracked as well as a resistor that was blown. Should I try replacing these or is there another problem that might make them blow again?
Edit: The resistor is a 4.7 Ohms flame-proof resistor. The capacitors are completely destroyed so I can't tell anything about them....Leave a comment:
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I'll try this when I can. Where do I ground the multimeter though? Also how do I check the caps with a multimeter?...Leave a comment:
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Yes, there's a TNY280PN. Its a small IC with 8 pins I think....Leave a comment:
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No, its completely dead with no standby power....Leave a comment:
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Just tried it and no difference. I should also mention that there are no visible signs of damage on the board and all the caps look fine....Leave a comment:
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Optiplex power supply dead
I have 2 Dell Optiplex 790 SFFs that both have dead power supplies. When I plug them in I can hear a spark so they are at least drawing power. I've checked all the power rails and there's nothing whatsoever. The self test button on the back does nothing also. I took it apart, plugged it in and probed the back until the voltage stopped at a mosfet. Is the problem with the mosfet or something else? I de-soldered it and when turned on it stays closed for about 4 seconds before opening again (tested with a multi-meter). The mosfet is this: [url]https://www.indiamart.com/proddetail/toshiba-k3878-mosfet-2853047252730.html[/url]... -
Hello, I'm here to troubleshoot power supply issues.Leave a comment:
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