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A few weeks ago I had a lady bring in her new HP and her old, dead, giant desktop. She was obviously a heavy smoker, as EVERYTHING was covered in not just dust...but solid dirt. Like it was carpeted.

I switched her data to the new computer, she left me the dead thing, so I decided to take it upon myself to figure out what I can do to get it running, inexpensively.

After some major cleaning (2 bottles of contact cleaner and 2 bottles of canned air) I set off on my journey to find the problem. Turns out its the power supply.

A new supply powers it just fine, i mean, it takes a little time to boot up but it works. The supply that came with it I've opened. I replaced a cap that looked blown with the same specs on another cap laying around the shop. The old supply will still NOT work to the fullest. It powers on, but it does not power the board enough to display on the screen/even get to a post test.

I'd really like to complete the project of fixing this, but I'm assuming its a small part that isn't doing the job. Anyone have any ideas on what it could be?

All the other caps, resistors, and theres a chip; all look good. there is one fuse I'm looking at replacing cause the glass is kind of foggy like its blown but the PSU does power on. its 430W and the new PSU is 350 and works, so i dont believe the wattage is an issue.

Let me know if anyone has a clue/ran into this problem before and found the solution. (Yes, i know alot of you will probably post get a new PSU as a response......I'm trying to avoid that).

I have caps and resistors galore at my fingertips.

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Last Post by wildgoose
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Unless you're actually skilled in maintaining equipment with mains voltages in it, then IMO it's best left well alone.

Unlike frivolous consumer notices like "may contain nuts" on packets of peanuts, when power supplies say "no user serviceable parts inside", they mean exactly that.

Washing, cleaning and poking the motherboard with a screwdriver might fry the mobo, but you'll be fine. The same is not true for a PSU.

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"Get a new PSU!" They're cheap!!!!


Sorry, I couldn't resist. You will find that the PSU's have mostly non-available components, and they're usually right to the edge of tolerance for cost savings in manufacturing to maximize profits.

The cap didn't blow because it felt like it. Typically the circuits being old, degraded, drew past tolerances and did a cascade failure. The cap is just the obvious problem. You'll most likely find the power transistors out, as well as a fused coil in the isolation transformer.

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