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My bench power supply decided to fry a board today
I was testing a laptop motherboard in my garage, had the supply set to 19 volts like always. Heard a pop and saw a tiny puff of smoke from a chip near the power jack. Turns out the voltage dial on my old unit had drifted high, it was actually putting out almost 22 volts. Had to spend the next hour finding and replacing that fried regulator. Anyone have a good method for checking power supply calibration more often?
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evan_grant704mo ago
Oh man, the ripple thing is something I learned the hard way too. Had this old supply from the 90s that looked fine on the multimeter, steady 12 volts, but when I hooked it up to an audio amp board it hummed like crazy. Turned out the filter caps were totally shot and it was pumping out AC noise on top of the DC. I actually rigged up a little test with an old car speaker once, just to hear if the supply was clean or not. Definitely not scientific but you can hear the difference when a cap is dying.
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zara_wilson6mo ago
Oof, that voltage drift is a silent killer. I mean, it's not just about checking the dial more often, maybe it's just me but I worry about the ripple getting worse as those old supplies age. A bad filter cap could send nasty spikes even if the average voltage looks okay on a meter. I keep a sacrificial cheap USB hub on the bench to plug in for a quick load test before the real thing.
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john_kim496mo ago
So you're telling me you keep a cheap USB hub around just to see if a power supply will fry it first? That's actually kind of genius, @zara_wilson. I guess it's better than watching your good stuff go up in smoke. My bench is already a mess of cables without adding more sacrificial gear though. Maybe I should just start buying old supplies in bulk and hope one of them works right.
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