[RESOLVED] (it was the CPU): Dead ThinkPad CPU? - Page 1
Forum section: electronics / general

author: lezginka_kabardinka
author_rank: Regular Contributor
timestamp: December 15, 2023, 06:13:03 pm
content: (it was the CPU)Thanks to all for the input, I solved this by Occam's razor logic, and going by what a ThinkPad expert had told me, elsewhere (and what sounded counter-intuitive to me) - "Try the CPU first" - yep, it went pop like a blown light bulb;can you Adam and Eve it!Got a ThinkPad L540, had it running for 9 months. The other day as I was using it, the screen froze and I held down the power to restart it... and BLACK SCREEN!Have checked/tested:~ LVDS (video ribbon cable to LCD) is fine~ RAM modules are fine (have also tested with OTHER "known good" RAM from my main laptop)It turns on, and if I remove RAM altogether, I get the (expected) 1-3-3-1 beep sequence which indicates "Hey! What's up? NO RAM?" etc. So it is doing SOME portion of the "POST" ("Power On Self-Test") sequence.i5-4210m is the CPU, have ordered a spare one from eBay.Any help (apart from "bake the motherboard in the oven to reflow" type comments) would be most graciously appreciated, thanks!

author: lezginka_kabardinka
author_rank: Regular Contributor
timestamp: December 19, 2023, 04:48:49 pm
content: No one at all?

author: Peabody
author_rank: Super Contributor
timestamp: December 19, 2023, 05:14:47 pm
content: Is it possible it's just the display back-light burned out? If you shine a flashlight on the display up close, can you see any indication that it's trying to display something?Have you tried connecting an external monitor?

author: lezginka_kabardinka
author_rank: Regular Contributor
timestamp: December 19, 2023, 06:05:58 pm
content: Quote from: Peabody on December 19, 2023, 05:14:47 pm~ No video detected (meant to mention that in initial post) - shone flashlight and another ring light, NADA.~ No go with VGA out; tested on a TV and an external monitor.Thanks

author: jmelson
author_rank: Super Contributor
timestamp: December 19, 2023, 06:21:34 pm
content: Does it have a spinning hard drive? If so, can you hear the drive seek during the boot sequence? If so, it is likely a graphics issue, and could even be a software issue where the windowing system fails to start. If SSD, then does the disk activity light flash?Jon

author: Halcyon
author_rank: Unknown
timestamp: December 20, 2023, 01:21:27 am
content: It could be any number of things.It's not impossible, but CPUs are extremely unlikely to fail. Aside from the days of the poorly designed AMD CPU's, I've never had a CPU just stop working in over 25 years.In rough orders of most likely to less likely, I would suggest:- Manifestation due to pre-existing damage (due to liquid or foreign matter ingress, exposure to extreme temperatures, mechanical damage...)- Corrupt firmware (although Lenovo's self-healing BIOS should take care of this)- Power supply or power regulation issue- Problem with the GPU or display circuitry- Fault with the motherboard or bad solder joint- Fault with the CPU

author: lezginka_kabardinka
author_rank: Regular Contributor
timestamp: December 20, 2023, 11:54:45 pm
content: (it was the CPU)Thanks to all for the input, I solved this by Occam's razor logic, and going by what a ThinkPad expert had told me, elsewhere (and what sounded counter-intuitive to me) - "Try the CPU first" - yep, it went pop like a blown light bulb;can you Adam and Eve it!