Member Avatar for TheKeeper

I have a Dell Inspiron 1150 which had a problem with the plug (solder cracked through normal use). I resoldered ii and put everything back together. Unfortunately, now the laptop won't start.

The symptoms are:
Power Light comes on.
Fan comes on for a while, then shuts down.
Screen is blank.
There are no warning beeps or blinks.
Power light stays on until the power button is pressed to turn the computer off.
The 3 lights above the keyboatd do not come on.

Things I have tried:
1) Powering up with only the power cord, and no battery
(same symptoms)

2) Powering up with the battery in, with or without the power cord
(same symptoms)

3) Removing hard drive, CD drive, and network card
(same symptoms)

4) Rearranging or removing RAM
(same symptoms)

5) Disconnecting the keyboard and touchpad cables
(same symptoms)

6) Removing LCD screen, stripping down to motherboard, and attaching external monitor
(same symptoms)

Just wondering if anyone can think of anything else I could try.

I did check the CPU to make sure it was securely seated against the heatsink - it is.
I have tried a new motherboard and am having the same symptoms.

Thanks.

- TheKeeper

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  • Latest Post Latest Post by finito

Dani AI

Generated

Given has already stripped the machine, tried an external monitor and fitted a tested replacement board, and rightly pointed out that an LED can be misleading, the next logical focus is the power-entry and low-voltage rails (the bits that live between the DC jack/battery and the motherboard regulators) and the embedded controller/BIOS that initializes the keyboard LEDs and POST. A board that only briefly powers the fan then dies usually means a rail collapses under load or the EC is cutting power to protect the system.

Suggested checks (ordered, practical, and safe for a hobbyist with basic tools):

  1. Verify actual voltages under load. Check the adapter and battery voltages with a multimeter while powering the laptop. Compare to the label. A green LED does not prove the adapter holds voltage under load.
  2. Inspect and reflow the DC jack area. Look for lifted pads, cracked traces or cold joints created during the earlier repair. Probe continuity from jack pin to the motherboard power input.
  3. Check the primary fuses and the MOSFET/regulator area near the jack for opens or shorts. Measure for a short between the main input rail and ground (with battery and adapter removed). An intermittent short will cause the behavior described.
  4. Confirm presence of standby rails (3.3V/5V standby) at test points when the adapter or battery is connected. If those are present but no POST, suspect BIOS/EC or a bad replacement board. If they are absent, the fault is in power delivery.
  5. Perform a CMOS/EC reset: remove the coin cell, drain capacitors (press/hold power ~30 seconds), then try booting from adapter only.
  6. If a current-limited bench PSU is available, use it to power the board and watch current draw. A high draw that drops the voltage points to a shorted component.

Tools and cautions: multimeter, magnifier, small soldering iron with flux, current-limited PSU if possible. Observe ESD and battery safety. If the power rails check out yet nothing posts, the fault shifts toward BIOS/EC failure or an incompatible/defective replacement motherboard; at that point swapping with a known-good donor board (or reflowing/reflashing BIOS by a skilled technician) is the usual next step.

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Member Avatar for finito

Well if it were a desktop machine I would suggest to replace your power supply. And seeing that there was a prior problem with that, it may just be that.

When you say you replaced your motherboard was the motherboard new or at least tested?

Member Avatar for TheKeeper

Yes, the replacement (not new) motherboard was tested.

I don't think it's a power supply problem because I get a green light on the front when I have the AC adapter plugged in. Also, when I have the battery in, I get a green light on the front for that (the right-hand one) so I think that's working too.

When I have the laptop on, nothing happens when I hit the Caps Lock or Num Lock keys. Those lights at the top of the keyboard should go on, shouldn't they?

Member Avatar for finito

From my experience the green light doesn't mean anything, I have had machines boot halfway with bad powersupplies, after scratching and banging my head only to realize that the powersupply was bad.

The keyboard not powering up only reinforces it. I don't work with laptops much but the concept is very much the same, If the power connectors are identical try and boot the laptop with a standard PSU.

Member Avatar for TheKeeper

Do you still think its the PSU if I have the same symptoms using just the battery?

Member Avatar for finito

The PSU is not the Battery or the Adapter.

I am not sure how it works for a Laptop, but it's combination of the two. So I guess the PCB controlling the Power Mechanism is faulty.

As I said I don't work on laptops. But My general understanding of circuits and electronics, I am sure there must a be an auto switch which automatically changes the power source. But the power delivery is a different part.

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