Customer ATX power supply came in with the complaint of intermittent no power. When testing it with power on, I could see that the fan is not rotating. Not only that, some filter capacitors also became bulge because of the heat accumulated inside the power supply. The failure of the fan would not suck out the heat generated by the components especially the switch mode power transformer.
If you switch off a working power supply and power removed, touch the power transformer, you could feel it is quite warm. Another heat source would be the heat sink where the output diodes attached to it. Diodes run a little bit hotter in filter circuit than diodes in other circuits due to the high current present at the secondary output line.
As for the malfunction fan, you actually could use a Philips oil based contact cleaner to service the fan. The grease inside the fan would run dry after serving for sometimes and eventually stop rotating. Remove the back plastic cap of the fan and spray it with the contact cleaner and you would be surprised the fan could actually regain back its glory. It will actually work just like a new fan. If it still doesn’t rotate, the best choice is to replace with a new fan. If you have the power supply that lying down at your work place then you could salvage the fan and install it.
From the photo at my website you also could see those decayed glue that stick besides the components. Manufacturers purposely used some kind of glue to apply on the components where they think those components will shake or comes out when there is vibration or during shipping. After the equipment work for a long time and the heat generated inside the equipment will turn the glue into conductive and sometimes would even corrode the pins of the components and eventually cause the equipment to stop working.
Scrap it off with your test pen and use Thinner solution to clean the printed circuit board. After replacing the capacitors, removed the decayed glue and service the fan, the Atx power supply again given a new life to faithfully serve the computer.
Some ATX power supply would take you a longer time to troubleshoot because of ‘too many’ components on the board. The most frustrated part is that you could not get the spare parts especially the power ic. Even if you could locate one, the price would be sky high and if this happen, I will usually get the customer to buy a new unit since nowadays the price of a new one are quite cheap.