Which device is causing this?

I have a computer with a flaky power supply. If the computer is unplugged for a while it will not turn on after it has been plugged in again until sometime has passed. About 10 minutes at room tepmerature. A couple days ago the power lines to my house came down along with the snow. The outside temp was in the low twenties. By the time power had been re-established the office temp was only about 25 degrees. In order to get the computer to start I had to direct the hot air from a blow drier into the back of the computer. After a few minutes it started up. So what device fails when cold? Eric

Reply to
etpm
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Bulging electrolytic capacitors in the power supply.

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

A degraded, old capacitor. Those, when cold, have a high serial resistor, and wont work properly. When you heat them, the resistor value will go down quite a lot, and things start working. A very common cause of equipment failure, very dependent on temperature.

Reply to
Sjouke Burry

Thanks Jeff and Sjouke. Now I know what to look for. Eric

Reply to
etpm

Try replacing the Power Supply!

Jamie

Reply to
Maynard A. Philbrook Jr.

You did notice that this is an electronics REPAIR group, right? Eric

Reply to
etpm

And the poster did a good job of conveying symptoms, but said nothing about looking inside the power supply.

That's a good indicator that they are't capable of component level repair, so "replace the power supply" was a suitable answer in this case.

One always has to read beyond the stated question, to evaluate what capability the poster has.

Michael

Reply to
Michael Black

Sure did and if you knew what you were talking about you would know that cost of labor investigating internals of a power supply over simply just replacing it has a broad dollar value. Labor is expensive but the cost of a replacement supply or just simply plugging in a test unit is much cheaper

Next time, think , think, and think again before opening the trap.

Jamie

Reply to
Maynard A. Philbrook Jr.

Since I'm going to repair it I have decided the labor is worth it. I suppose I should have said that I was going to repair this power supply. I did not say if I had looked in the power supply. I should have because I did. But it seems like I did not look closely enough. This weekend I'll take another look and hopefully find a bulging cap that I can replace. Eric

Reply to
etpm

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You can buy a 500 W power factor corrected supply from Newegg for $40 and T HEN get a $15 rebate. Buying good caps to redo your old supply will run $5- $10 and we haven't added the value of your time. Add another $5-$10 for a n ew cooling fan and you see how they are disposable.

You must be young enough that the 'satisfaction' of repairing it has value but you'll get over it. Personally I replace power supplies but replace cap s on motherboards to get going again. Repair the things that are hard to re place.

Also there are nasty Voltages in the power supply but none on the mobo.

Reply to
stratus46

e but you'll get over it. Personally I replace power supplies but replace c aps on motherboards to get going again. Repair the things that are hard to replace.

There is some satisfaction in the learning process itself though.

I hadn't realized at first but now obviously this is a PC but not a laptop. So I don't know if my observation applies here at all. But given our his tory with the kids's school laptops, the power supply and the power jack se em to be weak links. We've gone through a number of replacement wallwarts or equivalent, and have had several where the power jack connection eventua lly fails.

I guess there's no point making them bulletproof when the PC is obsolete in a few years, but it sure is annoying to have an otherwise workable machine unusable because you can't power it up.

Reply to
Tim R

I can also just grab a cap out of my box of caps. I guess 58 is probably young enough 'cause I'm still getting satisfaction from fixing and building things. I think by the time I get over it I'll be ashes. Cheers, Eric

Reply to
etpm

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d THEN get a $15 rebate. Buying good caps to redo your old supply will run = $5-$10 and we haven't added the value of your time. Add another $5-$10 for = a new cooling fan and you see how they are disposable.

ue but you'll get over it. Personally I replace power supplies but replace = caps on motherboards to get going again. Repair the things that are hard to= replace.

But you missed the point. You didn't do any analysis, it's not clear whether you actually understand even the basics of that power supply, you= =20 came here wanting a remote diagnosis, so you could "repair" it by changing= =20 the part specified. You didn't even use a specific subject header, you=20 used an extremely vague one.

Repair isn't just about changing parts, it's about figuring out what's=20 wrong. A lot of places do "repair" by changing motherboards or power=20 supplies, 21 years ago I got a Mac Plus because it had a problem and Apple= =20 wanted hundreds of dollars to change the video board. I opened it up,=20 figure out what was wrong, and fixed the problem, just a bad connector=20 that wasn't making proper contact. I had the skill, the Apple people had= =20 the "skill" to change the board, nothing more. So you could have made=20 this 'repair" by changing the power supply, and since you require=20 specifics from the crowd, you aren't really making a repair here, just=20 plugging in components, just a finer gradation than plugging in a new=20 power supply.

I've seen that "badcaps" site, lots of people with a little bit of=20 information, but they get lost if they fall off the path mapped out for=20 them. Or, they take that bit of knowledge about "bad caps" and think it=20 extends to all capacitors, when it doesn't. That's the future of the=20 world, the internet future where people think they are fixing things=20 because they can follow detailed instructions that someone else has=20 written down for them.

Michael

Reply to
Michael Black

Well Michael, I guess you're right. I don't know a lot about electronics but I can diagnose stuff. I tried to keep the subject header short which is why it was ambiguous. You are also correct that repair can be just unplugging (or unsoldering) a component or a whol system of parts, like the complete power supply. Since I donm't know a whole lot about electronics I asked here for information that would help me diagnose the bad part or device. Probably I should have posted the question in the basic electronics group too. In the end though I though Jamie was being a little flippant. I felt my reply was a little flip too. Now it has gotten out of hand. A more appropriate reply from me would to have asked Jamie if he was being flippant. If he wasn't then his answer would have been what he thought I was capable of, not an unwarranted conclusion. Cheers, Eric P.S. This weekend I will attempt to find the bad cap, unsolder it and replace it with a new one. If that doesn't work then it's time for Jamie's solution.

Reply to
etpm

I always seem to need odd form factor power supplies, and they aren't $25.

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Reply to
Michael A. Terrell

One more possibility ...

Most switch mode power supplies (well, most back when I was doing active repairs!) use a "kick start" resistor to bleed some wall current AC into the switcher, so that it'll start the cycle.

This used to be the most common failure point IME for cheaper switch mode power supplies.

I'd check that also, if you don't find any bad caps.

RwP

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Reply to
Ralph Wade Phillips

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