Member Avatar for hibbo102

The unit shut down on it's own during boot up, likely because it reached an over-temperature limit condition.

I've tried booting the machine from AC and from battery after the unit cooled. I've also tried holding the on switch for 5 seconds, but there is no indication of power getting to the machine: no lights turn on, not even a flicker.

Any ideas?

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  • Latest Post Latest Post by Kegtapper

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The symptom described by — a ThinkPad T40 that died during boot and now shows no LEDs or fan activity — narrows the fault set: this behavior most often points to power-delivery or motherboard-level failures rather than an OS issue. The replies from and correctly move the thread toward hardware isolation; the following expands that into a concise, practical troubleshooting sequence and cautions to help reach a fix or decide on board-level repair.

Suggested diagnostic checks and sequence:

  1. Confirm the AC adapter actually produces the voltage printed on its label (multimeter). An adapter LED can be helpful but is not definitive.
  2. With battery removed, test for any standby voltage at the DC jack or nearby board test points. Absence of standby usually indicates a fault in the input/power section (jack, fuse, MOSFETs, or PCB trace).
  3. Check board fuses for continuity and measure resistance between main positive rail and ground to detect a hard short. Use a current-limited bench supply for controlled powering if available.
  4. Visually inspect the input/power-management area under magnification for cracked joints, lifted SMDs, burnt traces, or bulging capacitors. This complements @Kegtapper’s observation that intermittent solder/connection faults in the power area are common.
  5. If a suspect solder joint or component is found and soldering skill/equipment is available, use flux and a temperature-controlled iron to reflow; otherwise the repair should be performed by a technician.

Notes and cautions: an immediate total-loss-of-power is less consistent with simple CPU overheating (thermal shutdowns normally allow some LEDs/activity for a short time). Work on live circuits only with appropriate knowledge and ESD precautions. If adapter and standby rails are present but the machine still shows no signs of life, the fault is typically board-level and often requires component-level repair or motherboard replacement; weigh repair cost against machine value.

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Member Avatar for ian_tec234

Try removing the memory modules and power on with your battery alone or ac adapter. If you can swap a known good battery that can isolate things more. Is the AC adapter LED light solid by the way?


Good luck

Member Avatar for Kegtapper

If you have opened the machine - check the coils. Bad solder on one pad. There are about 4 of them and should be on the right side near DVD/Extra battery power connector. Check the top and bottom sides of the board. They are rather large by comparison to the rest of the parts on the board, and if you can lift one side of the coil with your fingernail, that is the one. This was just discovered last week by me, on several motherboards that I had in the pending stack.

Member Avatar for cguan_77

CPU over heating? or do as suggested in post #2 :)

Member Avatar for Kegtapper

1 - it is not an overheating problem. (Overheating was a guess)
2 - If a unit is overheating, it should still take about 2min before shutdown even if the fan is not working at all.
3 - my previous suggestion is a known problem. And had been recognized on several models doing the same thing.

I have repaired over 500 laptops and recognized the pattern of manufacturing failures in Thinkpads, Gateway, HP and the other common brands.

Disassemble the unit and check the larger coils (indicated by L1, L4 or something) they will be grey and 4 sided. One side is lifted -no contact. When the current tries to go though it, it warms up, and the connection breaks. Check and see!

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