Hi, my Dell Vostro 2420 is completely dead, with no indication of power going in. The AC adaptor is fine, battery ok but still no power. It came on after a week of going dead but then after powering on for about 7hours, the machine went completely dead after switching it off again & trying to restart.

Check that the vents are clear. Get some compressed air and blow the system out to help clean it - taking the cover and keyboard off is good so you can blow the motherboard clean. If it is still dead, then you will need to send it in for repair.

Thanks Rubberman have done that but still nothing.

Im thinking of dry soldering the power input area of the mother board. What do you think.

If you know what you are doing, then fine. I wouldn't, but my grandson would. He is much better at that sort of thing than I am as he designs and builds his own PC boards for drone aircraft control systems.

Thanks rubberman. Would you mind some advice from your grandson.I would really appreciate it.

Thanks again

Urg. Could be anything. Dry solder joints are more common than you would like to believe. A tiny trace of corrosion around low power joints, hydrated salts remaining from cheap flux, dodgy connectors, the mb monitor chip, the ps's controller chips. Tap those chips briskly with a pen - they sometimes go "microphonic", meaning an internal pin out connection or silicon junction is intermittent.
I'd check if the PS was receiving a PSGood signal from the mb, and if so, was generating all requisite voltages. And if so, then I would sigh and consign the thing to a bin. Power supplies I can do; I cannot work with components that I can barely see. Others may be able to. There are in use components that are sub-millimetric now... :(. Interestingly, they are more reliable than their larger kin (it's a heat thing), but impossible to work with manually.