When there's a big green flash from a PSU...

[biggles1000]

(I'm guessing this thread would go there as it isn't really an overclocking thing, but part of the internals of a computer)

I bought a 500W PSU for my computer. It was too big for my apparently shorter than standard case, but when I was building my computer I flicked the red switch on the back (the europe to US voltage one) with it switched on (but the system wasn't functioning). There was a big green flash and a slight pinging noise.

Just wondering, is that PSU totally done for?

 

[Mike Connor]

Probably. You should NEVER attempt to switch voltages or do anything else at all like that with power connected to the machine.

This is not only because it is likely to fry your machine, but because it is also likely to fry YOU !!!

The big green flash was likely a condenser or other component exploding. The green colour is usually caused by copper vapourising. If you sniff the power supply AFTER SWITCHING OFF ANY POWER AND REMOVING THE PLUGS FROM WALL SOCKETS ETC and it smells odd, that is usually the heated and splattered contents of a ruptured condenser.

However, other components can also explode or short circuit if you try to switch voltages with the power connected. This can also destroy various chips on your motherboard.

Also, if you switch input voltages to lower voltages than you actually have available, the power supply will fail catastrophically when switched on.

For instance, if you have switched the PSU to 110V input, and you plug it into a socket with 230V then something is likely to explode. Even if nothing apparently happens, the PSU is in any case completely unserviceable as a result. This too can also destroy various other components.

Regards....Mike Connor

 

[wilywombat]

Unless you are good at fixing PSU's then I would guess that the answer is yes...Time to go buy a new one!

 

[biggles1000]

Probably. You should NEVER attempt to switch voltages or do anything else at all like that with power connected to the machine.

This is not only because it is likely to fry your machine, but because it is also likely to fry YOU !!!

Regards....Mike Connor

ok, thanks
I guess I should consider it a lucky escape and be more wary next time

Unless you are good at fixing PSU's then I would guess that the answer is yes...Time to go buy a new one!

Well I took it apart afterwards (being careful with what I touched) and the fuse didn't look blown. any idea what would be damaged?

 

[biggles1000]

...The big green flash was likely a condenser or other component exploding. The green colour is usually caused by copper vapourising. If you sniff the power supply AFTER SWITCHING OFF ANY POWER AND REMOVING THE PLUGS FROM WALL SOCKETS ETC and it smells odd, that is usually the heated and splattered contents of a ruptured condenser.
However, other components can also explode or short circuit if you try to switch voltages with the power connected. This can also destroy various chips on your motherboard....

ah. so I'm guessing it isn't fixable/would be very hard to fix?

 

[wilywombat]

The amount of grief and time wasted fault finding and spare parts does not equate to the cost of buying a new one.

 

[biggles1000]

The amount of grief and time wasted fault finding and spare parts does not equate to the cost of buying a new one.

well it did only cost £15, so I suppose 'no point crying over spilt milk'
I guess i'll buy a new one when I buy a new case - this time i'll know to match the sizes

 

[ignatzatsonic]

I've never heard of any ordinary user repair or maintenance of a PSU other than replacing the fans.

Consider it a lesson learned and look for a replacement.

 

[biggles1000]

I've never heard of any ordinary user repair or maintenance of a PSU other than replacing the fans.

Consider it a lesson learned and look for a replacement.

will do
just glad I didn't blow any of the other components... :S

 

[Mike Connor]

Probably. You should NEVER attempt to switch voltages or do anything else at all like that with power connected to the machine.

This is not only because it is likely to fry your machine, but because it is also likely to fry YOU !!!

Regards....Mike Connor

ok, thanks
I guess I should consider it a lucky escape and be more wary next time

Unless you are good at fixing PSU's then I would guess that the answer is yes...Time to go buy a new one!

Well I took it apart afterwards (being careful with what I touched) and the fuse didn't look blown. any idea what would be damaged?

Switching power supplies are only serviceable by a qualified electronics technician. Trying to do so without the required knowledge and equipment is extremely dangerous and unlikely to work.

Usually, the "big green flash" is caused by an exploding condenser, ( AKA Capacitor), this also tends to spray the circuit board with the contents and produce a nasty smell. Switching power supplies that have been subjected to catastrophic failure in this manner are theoretically reparable, but it is not worth the time and effort involved to try. Not even for a qualified technician. The unit would be replaced.

EDIT: Because it may be of general interest. Switching power supplies function quite differently from transformers and similar equipment. Highly specialised equipment is required to test them. They only work properly under very specific load conditions. Repairing such equipment is completely outside the scope of any hobby computer builder.


Some more information;

http://en.wikipedia.org/wiki/Switched-mode_power_supply

http://en.wikipedia.org/wiki/Power_supply_unit_%28computer%29


Regards....Mike Connor

 

[biggles1000]

thanks. I'll bin it then