Member Avatar for Stabu

I literally pulled this laptop from the dumpster. Seems like an interesting project. The confuser displays symptoms similar to the no power issues and fixes listed all the web with some twists. Plug it up to AC with a battery I get the plugged in led and the battery charge light. The unit does charge the battery. Hit the power button on or off AC power and the hard drive spools up but the power light does'nt come on nor does the hdd led flash. So I tore it apart to see what was goin on in there. The DC connector looks fine. Nothing burned or smells burned on the board. When I put power to it I see the cpu fan run for a couple seconds and stop. The fan on the power supply side next to the CMOS battery does nothing. All thats on the power supply side a a few diodes and resistors. I did notice a SMD 5A 125v fuse. Thinking that was the issue having seen it in playstations I jumped it. It made no difference to the issue. So my thought process here is there is something awry in the power supply circuit and it is repairable without resorting to a whole new system board. Voltage is being fed to the charger circuit and hdd fine. The feed to the "mainboard" has an issue thus the no boot, power light or cpu cooling and power supply fans. So my question is does anyone here have experience at the component level that could give some advice on what the culprit is. For the record I'm not scared of a soldering iron nor do I have anything invested in this project beyond a CMOS battery. So risking frying this system board is no real concern to me. At this point in its current state Compaq recommends replacing it anyway. However, I would much rather invest in a .39 part instead of a replacement board from Compaq to the tune $685. Thanks

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Useful next steps that build on 's basic checks and move into component‑level diagnosis for an Evo-class board.

Start with measured voltages and shorts rather than parts swapping. Verify the adapter at the DC jack under a small load, then probe the board: measure the input rail at the jack/battery connector, then look for the standby rails (typically a 5VSB or 3.3VSB) at the SuperIO/EC and the BIOS/RTC area. Use a multimeter to check DC resistance from each major rail to ground — a very low ohms reading flags a shorted device. A current‑limited bench supply (or an inline fuse/resistor) is invaluable to apply power safely while watching where current is drawn.

Focus inspection and measurements around the DC input filter, the input fuse/polyfuse, the main MOSFETs/diode pack that feed the VRM, and the switching regulator ICs. On older laptops common failures are shorted MOSFETs or diodes, blown tiny SMD protection fuses, and bad electrolytic/tantalum caps; cold solder joints at the DC jack and large connectors are also frequent culprits. Use diode mode on the meter to spot shorted MOSFET body diodes and check regulator IC input vs. output pins for expected voltages (no main rail outputs with standby present usually points at the power enable/control stage).

Practical tips: document every voltage and where it was measured, photograph suspect areas at 10x magnification, replace inexpensive parts first, and only bridge pads (power‑on pads or fuses) with care and a solid plan. If component tracing and replacement is impractical, salvaging a donor board or a cheaper used motherboard is often more cost effective than full OEM replacement.

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Member Avatar for BuggZ

Before you get out the soldering iron, you should check the basics first. Make sure the power supply is the correct voltage for your laptop. Remove the AC adapter, battery and memory and press and hold the power button for 3 seconds. Try starting the laptop with the AC adapter connected but no battery installed, then try with the battery but no AC adapter. Try reseating or swapping the memory with known good memory. Make sure the memory is the correct speed for your laptop. Try starting the laptop with the hard drive, CD, and floppy disconnected/removed. Reseat the processor if it is not soldered to the motherboard.

Member Avatar for BuggZ

Sorry but previous post should read "Press and hold power button for 30 seconds."

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