UKC

I have an ancient Dell Latitude E5540 laptop that won’t boot. It was working ok then I disconnected it from the power and put it away whilst I was away on holiday. When I got back and tried to power it on it was dead. No lights, no POST, nothing. I’ve tried various obvious things: battery, power supply, replacing CMOS battery, various power-on reset sequences etc and no joy. The original CMOS battery must have been 9 years old. Any further suggestions?

I did find a video of someone fixing the same problem on an E5540 but the trouble is it’s in a foreign language, Hindi I guess. It looks like he just strips out the motherboard, powers it up and everything is fine again but I must be missing something in the voiceover! Anyone speak Hindi or want to take a guess at what happens at around the four minute mark please? Long shot I know…

https://fb.watch/te3NVaSDDs/

Try removing the battery and just powering up from power supply only.  Sometimes a dead battery can prevent anything firing up.

In respect of the battery, what exactly did you try? Have you got a known good one?

Tried that thanks. 

Yes, I tried a known good one. 

Just tried a different power supply that has a light on it. It trips off as soon as I connect it. So that’s probably a short somewhere? It’s going to be the motherboard isn’t it…

Had a similar sounding issue with son's laptop (different brand). He spilled some water into it a while before and all seemed dried and fine and no harm done for ages, but then it died. Once open up I could, with a lot of difficulty finding some corrosion/scunge on motherboard between 2 components that caused a short, scraping off the corrosion and cleaning the gap and it was fine afterwards. If it's like my son's one, it could be a physically tiny fault

It turned out to be the motherboard. I sent the laptop away to a chap who replaced a shorted capacitor on the board for £80 and all is well again. 

Good bit of fault-finding by the repairman. I'm pleased that's worked out.

The capacitors are quite a common point of failure apparently. Having watched a couple of YouTube videos the bit that impresses me most is the small-scale soldering whilst looking down a microscope. I’ve done a fair bit of tricky soldering before but I could see this was well beyond me. It’s mildly annoying when I come up against a DIY job that I don’t have the skills or equipment to take on but there’s satisfaction in knowing when you’re beaten and getting someone else to do it!