switch mode power supply common werid bug? or something else (computers, etc) - Page 1
Forum section: electronics / projects

author: CopperCone
author_rank: Super Contributor
timestamp: March 09, 2018, 12:34:12 am
content: So I have a computer, and a piece of test equipment (which uses a switching power supply), that basically have this problem that sometimes if you unplug em while their running, and reconnect them, they wont work, but if you leave it unplugged for a while (like 30 minutes), they will run just fine when you turn em on.I don't think its a thermal issue, it seems to be triggered when power is lost, and the solution is just to leave it off for a while.Some kind of charge leakage some where?I have been running on a generator because of a storm, and it fucked up a few times, and every time i lose power I gotta wait a while to be able to turn this computer on..........its like a hysteresisthat computer also used to have a problem if you turned it off, and turned it back on too quickly, it would get stuck on boot. That went away though.. and this is the new problem.. sometimes.The test equipment spectrum analyzer used to have this problem, but I left it powered on for a month and it went away. Like something self healed inside of it while it was powered on.

author: BrianHG
author_rank: Super Contributor
timestamp: March 09, 2018, 12:56:28 am
content: Quote from: CopperCone on March 09, 2018, 12:34:12 amIs it one of those modern generators which produces a stepped, buzzy, square wave output, or, a true sine wave?240v, or 120v?Could the L and N be backwards on the generator?Does it have a true GND, or a center tap GND/Earth pin?These are the things which I think may trigger a MOV and self-resetable fuse when a power switch or AC plug is pulled.

author: CopperCone
author_rank: Super Contributor
timestamp: March 09, 2018, 12:59:22 am
content: Honestly I don't know the answer to any of those questions and there is snow on the ground plus its running, but these problems I had occurred without it (though maybe more frequent now?).I just lost generator power like 3 times today, so the issue came up, but I meant to make this thread YEARS ago.

author: BrianHG
author_rank: Super Contributor
timestamp: March 09, 2018, 01:32:17 am
content: Does your generator make you appliances buzz?Like a microwave oven's fan would sound a little slow and the transformer would buzz instead of like normal.I'm sure you could have tole me if you were using 120v...What's the model of generator?

author: Blinkenlights
author_rank: Contributor
timestamp: March 12, 2018, 11:53:31 pm
content: It could be a PTC tripping out - a self-resetting fuse.I find they self reset in about 30 seconds, not 30 minutes, however.30 minutes DOES sound more like an SMPS latch-off function that is only fixed by discharging the power supply completely.In any case, to find if it is a PTC, carefully run the gear outside of its case. Use a non-contact thermometer (IR gun type thermometer) to read the temperature of what you suspect are PTCs - they are disk type or square type radially mounted, usually yellow. When they are tripped out they run at 125 degrees celsius, and as the rest of the unit will be cold they will show up easily - but the whole point is the equipment must be live, so be careful.If the problem is an SMPS latch-off that is staying triggered, add a discharge resistor across the reservoir capacitor. However, there should be one there already. Maybe it needs to be heavier.