Toshiba Satellite A300 - HDD power

[czoran]

Hello,

I have Toshiba Satellite A300 which fails to detect hard disk.
Laptop had water (juice) damage.

I cleaned motherboard and keyboard. Everything is working except it won't spin up hdd. Serial ATA power connector is giving 4.05V instead of 5V and disk is not spinning. Disk is working fine in another laptop or over the USB in same laptop. It detect CD/DVD drive, but won't boot of it, because can not spin it too. Same 4.05 volts there.

Do you have idea what could it be? I am measuring that 4.05V on several places over board and not know what is causing such drop. Nothing overheats, checked all capacitors with ESR meter, all OK, checked few mosfets, all OK. Even replaced some of them with new.

I tried booting via USB with linux live (knoppix, ubuntu) and everything else seems to be fine: sound, graphics, mouse, usb, touchpad, keyboard, bluetooth, lan, wlan, card reader.

Thank you very much.

Regards,
Zoran

[shadow]

Re: Toshiba Satellite A300 - HDD power

Wow what a weird problem. Hopefully someone can steer you in the right direction. At least you know why the discs are not spinning (not enough voltage). Only thing left is to find the culprit.

Careful circuit tracing would eventually lead you to the cause, however this is quite difficult (i would think at least).

[czoran]

Re: Toshiba Satellite A300 - HDD power

Yes, really weird situation. I would be happier if there were no voltage at all, if something burned, etc. )

[Wizard]

Re: Toshiba Satellite A300 - HDD power

I advise you to start at the switching voltage regulators where low voltage is from for the 5V. This is the ones with square or round dark grey material are inductor coils with arrays of ICs around them. Probe either side of the coils till you find the 4.05V then focus on cleaning more carefully with more water then dried with alochol on the controller IC for that 5V in the feedback circuit. This will be same circuit that senses the 5V and control the array of MOSFET ICs (transistor switches) that chops the battery/charger voltage and fed chopped pulses to the coil. I bet you will
find some remaining spill there.

Cheers, Wizard