There aren't too many parts in there so one thing you could try is just measuring everything you can. Resistors, diodes, etc. Make sure to discharge the big caps before attempting this (although with a short circuit like that there probably won't be much charge in there). If any part seems wrong, de-solder it and measure again.

There's also the hardcore method: connect a >120W light bulb in series and see where the smoke comes from.

First I recommend stop changing the fuses, it won't fix the problem that causes the fuse to blow and might cause more damage.

The picture is bad but if you say nothing looks broken then it is something you just have to trace otherwise. Can be a bit tricky unless switching mode power supplies are somewhat familiar. I would first use a multimeter to check if the mains rectifier diodes and the bulk storage cap are good with no short circuits. If those are OK, then the actual switching controller chip might be broken so it drives the switcing transistors incorrectly or the switching transistors are blown. If replacement parts are not available then they could be sourced from other power supplies.

If the form factor is weird, can you fit the electronics of another working powersupply into that case?

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Something is shorted so stop trying to power it. Likely candidates are input side rectifier, input side capacitor and switching transistor.

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KieranD212 wrote:

smeezekitty wrote:

Something is shorted so stop trying to power it. Likely candidates are input side rectifier, input side capacitor and switching transistor.

If you read the posts i've already found the switching transistors to be dead, i also already stopped changing fuses and powering the psu before i made this thread.
I just need to figure out a replacement. It says PECOR PED7491 B0457 on the transistors.

Those old transistors are often not made anymore. The PED7491 is included
A quick search shows it can be subed for a NTE2311 but a bit spendy: http://www.ebay.com/itm/NTE2311-NPN-SWITCHING … G-/261502042293
I strongly suggest you check the rectifier and filter caps still because they could be damaged

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Little off topic, but at a local thrift store I saw an XT supply just sitting there.. and I got it for 20 cents

http://www.americanmicrosemi.com/information/ … /?ss_pn=PED7491

Utsource has the original part in stock: http://www.utsource.net/ic-datasheet/PED7491-1531128.html

Make sure to check all parts in series with this transistor too before powering it up again. The PWM controller or feedback circuit could also be damaged, driving the transistor wide open and frying it again right away. A short or open-circuit on the secondary side of the transformer can do this too.

This is where the light-bulb-in-series trick comes in handy: with a low wattage bulb you won't risk frying anything, and have a simple current indicator too 😉

http://www.fairchildsemi.com/search/controlle … x=0&textBtn.y=0

The Fairchild FJA13009 is also a suitable replacement. About $1.50 on Digikey.

The Sanken 2SC4140 would also do and can handle a lot more current (18A vs 12A) and lower VCE (possibly more efficient/less heat) but more expensive (~$4.20)

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DS4004 is probably 1N4004, which can be replaced with the more common 1N4007.