what happens when a psu gets hot?

dpopiz

Diamond Member
Jan 28, 2001
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what will happen if my psu overheats? will capacitors pop? will it just burn out? will my comp get damaged?
ALSO: what in the psu generates heat?
 

CTho9305

Elite Member
Jul 26, 2000
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transistors (and rectifiers) create most of the heat. When the psu overheats, the transistors stop performing properly.
 

RossGr

Diamond Member
Jan 11, 2000
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As Ctho said, it is the transistors which are disapating the heat. They are acting as voltage regulators, the supply feeds a higher then necessary voltage into the regulators, which then able to hold a constant output inspite of a varing current load. This difference between output and input voltage is a source of heat.

The components on your motherboard need to have a constant DC voltage for proper operation. When the PS overheats a regulator could fail, this failure could mean that the higher unregulated voltage gets through to your motherboard, the results of this could be a fried CPU or memory or virtually any device on the motherboard. The regulator could also simply fail to hold a constant voltage giving you lockups or corrupted data.

Very few good things happen when a PS fails.

BTW the phrase PSU grates on my nerves, the device is a power supply, or if you are as lazy as I am a PS, the U on the end, I suppose stands for unit but is totally unnecessary. I have been working on power supplies of various shapes and sizes for over 30yrs now and have never felt the need to specifiy that it is a unit. :)
 

Mark R

Diamond Member
Oct 9, 1999
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Heat is produced by all the active circuits within a PSU.

The main sources are the switching transistors and rectifiers. Other significant sources include the inductors (resistive and core losses) and capacitors (ripple current losses).

High temperatures may damage any component - often the transistors will go first, as they get hottest. When a transistor fails, high voltages may be directed onto low-voltage circuits, causing catastrophic failure of capacitors and other components.

In the longer-term, capacitors are the most affected by high temperatures. The hotter a cap gets, the less time it lasts. The most likely effect of this is that its energy storage capacity gradually fades, and the voltage regulation ability of the PSU gradually deteriorates.

Good PSUs will have an 'overvoltage crowbar' circuit connected to the ouput. This circuit is seperate to the normal monitoring circuits, and is a fail-safe, preventing damaging voltages reaching the output. If the PSU malfunctions and produces a high voltage, the crowbar will kick in, and short-out the PSU; the PSU may shut down or be destroyed by the protection circuit.
 

dpopiz

Diamond Member
Jan 28, 2001
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thanks a lot for the excellent detailed explanation your sent me in email (actualnamenospam@wmconnect.com, whoever that is)
why don't you post it here for everybody to see?
also, you say good psus will shutdown if they sense temps too high or voltages too high. does anybody know if my antec sl300s would have that?