Member Avatar for JD4121

I recently removed, cleaned, and reinstalled the heatsink on a Toshiba 2435-S255 laptop. I was very careful, made sure I was properly gounded, never removed the uP, all this good stuff. After putting it together it powers up but never boots. It doesn't even go into BIOS. Not sure what went wrong. Any thoughts?

Further, if the BIOS battery is dead, how can I find it? I removed all covers and such, but cannot find it. Any comments where to look?

Thanks.

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  • Latest Post Latest Post by caperjack

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A few focused checks that often solve a laptop that powers up but never reaches BIOS.

First, do a careful visual inspection around the heatsink and the areas you removed to get there. Look for any stray screws or metal debris under the board, blobs of thermal compound off the die, lifted or cracked PCB near the heatsink mounting holes, and any ribbon/flat-flex connectors whose locking tabs are not fully engaged. was right to flag connectors — expand that to check the power-button board ribbon, keyboard/palmrest ribbon, display cable, fan power lead and the HDD/ODD ribbon or connector.

Isolate the machine to a minimal configuration: remove HDD/ODD, wireless cards and all removable peripherals; leave only one known-good RAM module (try each slot); connect AC (no main battery) and try to power on. Listen for fan spin or beep codes and watch any LED pattern. If nothing changes, perform a power-discharge: unplug AC, remove main battery, hold power 30 seconds, then try again with AC only. If the unit posts with no drives and one RAM stick, add components back one at a time to find the culprit.

About the CMOS/BIOS battery: on many Toshiba Satellites it’s either a small coin cell in a holder, a two-pin wired cell tucked under the keyboard or palmrest, or a small wrapped “pouch” battery that may be soldered. If it cannot be located from the bottom covers, the keyboard/palmrest usually must come off. If the cell is soldered, replacing it is a board-level job.

Finally, rehearse the heatsink reassembly: clean mating surfaces with 90%+ isopropyl, use a thin, even layer of non-conductive thermal compound, and tighten screws gradually in a cross pattern. If no POST after the isolation steps or if you find physical damage or soldered CMOS you’re unsure about, professional board-level diagnosis is the safe next step.

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Member Avatar for sparksterz

When you say you cleaned it, what did you use to clean it?

Member Avatar for JD4121

I removed the heatshink and blew air through it to clean it. Then reinstall the heatsink. I've done this before (about a year ago) successfully, but this time the machine will not boot.

Member Avatar for caperjack

a computer will still boot with a dead bios battery ,it will just revert to the default bios settings each time you reboot comp!
most likely cause of your problem is a small ribbon or some other wire not hooked back up or broken off even .

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