pc power supply short circuit mishap

Inside the power supply, there should be a fuse. In many of these supplies the fuse is a wired type fuse (pig-tail fuse). It will be soldered to the circuit board with its wires. Normaly, if the power supply fuse is blown, there are more serious problems than just the fuse.

Take care that inside of a computer power supply there are very high voltages, and it can give a very strong shock. There are serious safety issues with these supplies. These supplies are designed to not be serviceable.

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JANA _____

I'm sorry for my low level knowledge about electronics. I hope this group can help me. I use a compaq Tower PC from 1998.

It still functioned admirably, but I had connected a fan to one of the 4 cable (red black black yellow) plugs which also go into hard disk and cdrom drives, using wires I put loosely inserted into the plug.

Unfortunately, I caused in this plug a short circuit by pulling the loose wires which connected this fan to the plug and had the red and black ones touch each other for a second.

However stupid this may be, I first thought no damage was done to the power supply. However, the ATX motherboard power switch did not start the computer no more. I thought the motherboard was gone as well by then.

I bought a new power supply, and the problem is over, for now.

I still hope I can fix the first, older power supply, because the new power supply stated on the box that there was protection against short circuits.

Is it possible that only the small fuse in the old power supply has blown, or that I can repair the power supply ? The short circuit i caused only lasted for a second maybe.

MTIA,

peter

Hello

and thanks "JANA" schreef in bericht news:Wu-dndZssrRoYqrVnZ2dnUVZ snipped-for-privacy@posted.uniservecommunications...

The fuse is of the small glass cylinder type with metal ends. Indeed, I fear that if the unit is damaged, just replacing the fuse could mean other damage to the pc to be caused by - I think - changed voltages or so.

I don't take any chances with this old but useful pc, I hjust replaced the power supply and won't repair the old one.

Rgds,

Peter

Well, a power supply with all outputs shorted together should never cause any power supply damage and not blow its fuse. These requirements have been standard even long before PCs existed. But when selling power supplies to A+ Certified computer techs, many supplies are missing these required functions.

Maybe the fuse just blew due to a manufacturing defect. Or maybe the fuse blew do to a power supply missing required functions. Nothing posted here provides any facts to answer that question.

JANA is quite correct about caution. To create 3.3, 5, and 12 volts, the power supply must first create 300+ volts from 120 volts. That

300 volts could remain even when power cord is removed (especially if cost controllers selling to A+ Certified Techs forgot to include that required part). Just caution is required. But then a power supply must have all outputs shorted together and never fail. So why did that power supply fail? Was it missing essential functions to sell for less than $60 full retail?

Replacing the power supply with one from a responsible manufacturer might be a better solution.

Hello, and thanks to all,

"JANA" schreef in bericht news:Wu-dndZssrRoYqrVnZ2dnUVZ snipped-for-privacy@posted.uniservecommunications...

Could more serieus problems indicate that it would be a hazard to the motherboard from the pc to change the fuse and reconnect the power supply to the motherboard ? Could it be that voltages could have changed, or so ?

designed not to be serviceable ? Do you mean that repair of such units would deliberately have been made impossible ?

Thanks again,

Peter

Designed not to be serviceable means that failure should not happen and that a human who might replace that fuse should understand why (and where) 300 volts is dangerous. As JANA noted, a most common reason for fuse failure would be due to other defects inside a supply. Failures that cannot be solved or explained to anyone who asks the questions that were asked here.

Yes, fuses sometimes fail for no other reason - rarely. One might get lucky - replaced fuse failed only due to manufacturing defect. Due caution should be exercised. Nobody is suggesting that solution.