Saturday, April 23, 2011
Compaq C500 - LED's Flash Rapidly, and never posts or starts
Unit arrives with following symptoms:
Flashing LED's on the power panel, and the power LED on the front edge flashes continuously. [See video]
When I connected the DC source with the battery inserted, I thought the charge light would come on as it should regularly. Since it didn't and flashed at the same rate as the other LED's this told me what area to check. When checking the MOSFETs PQ5, PQ49, and PQ4 all of them were of the same type [FDS4435] but PQ49 had a short in both directions with meter set to DIODE mode. This indicates the FET is shorted. So that was the first thing to replace and test again.
When I replaced the PQ49 FET and plugged in the charger (with battery inserted) the charge light came on, as it normally should. Upon powering the unit, it posted normally on external monitor.
Since it was a power in/charge circuit I assumed everything else was fine and reassembled the unit. All items work. USB/Wifi and other peripherals. So the unit was tested with OS loaded and everything fine there, and allowed the battery to fully charge.