Long term EEV blog viewer but first time poster here, my hobby is mainly arcade PCB repair which I have been doing for about 5 years now. Unfortunately my test bench arcade PSU let the magic smoke out recently, and vaporised its fuse. The fuse didn't just blow, it was totally destroyed, just the end-caps remain and glass dust.
I was hoping to fix it as it is one of the older ones and seems much better built than the flimsy modern ones available.
Ignore the resistor lead that looks like its bent onto the power transistor, that's a leg I lifted during troubleshooting and the angle of the photo is deceptive.
What is bugging me is the sheer amount that seems to be wrong with it, half the bridge rectifier diodes are short circuit, which is what I assume blew the fuse, and there is a lump blown out of the surge suppressor resistor, which I guess occurred before the fuse opened.
So far so good, but a number of other resistors throughout the unit are also totally short circuited, without a mark on them, from a couple of quarter watt ones, up to some of the 1 watt ones. Am measuring these out of circuit (one leg lifted) by the way.
The only build issue seems to be cracked joints on a single decoupling electrolytic on the output of a 7805 but I doubt that had anything to do with the cascading failure due to where it is located. All other electrolytics seem fine based on their ESR anyway.
My question is actually whether anyone more familiar with switch mode PSUs has come across failures like this? It seems unlikely that so many resistors would go totally short circuit without any physical signs of trauma. None of the transistors or voltage regulators appear to be shorted so am also curious as to what was the first failure that set off what looks like a chain reaction.
Any advice would be appreciated, beyond the obvious "bin it", which is a conclusion I am almost at anyway.
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