Hello everyone,

This is a long shot ,but does anyone know what the 6pin arrowed component is ?
I received a laptop recently and this is the fault on its hard drive
causing it to be totally dead with a burnt component smell.
The board uses 2 of them and they are marked 642 followed by an upward chevron.
I have attached 2 pictures with arrow to 6pin mystery component.

Thanks for looking.

Vic Pearson.

Most probably it is not the unique component at fault according to the failure because how the circuit is designed / made. I think the laptop had serious problems too, otherwise if it was a drive only failure it is very rare if there is no external cause i.e. spilled liquid or short circuit , at least in my stats and I have seen hundreds of these drives. Nevertheless, it happens.

P.S. replacing the PCB straight away work in 5 -10% , too many things must coincide otherwise the drive won't work.
P.P.S. before buying replacement parts, need to know if drive internals are OK otherwise you will screw the new PCB.

P.P.P.S. I don't know NOTHING so don't ask

For what BlackST told you, your best option should be send the drive for diagnosis to a DR company, instead of spending money and time for nothing.

It's what usually people don't want to hear...

The 6-pin component appears to be the MOSFET chopper in a DC-DC converter, possibly the Vcore or Vio supply for the Marvell MCU. The component below it is the Schottky flywheel diode, and 4R7 is the inductor.

It would help if you could upload a photo of the area around the other MOSFET.

You could also locate the supply pin of the SDRAM and use a multimeter to test for continuity between it and the coil(s) in the DC-DC converter(s). This will enable you to determine the output voltage of the converter.

I suspect there may be a small smt fuse near the IDE connector. Once again, more detailed photos would help.

_________________
A backup a day keeps DR away.

Imagine how a schematic could help...

I am much encouraged by all your replies and they are all
much appreciated.
The laptop works fine with another drive so its a definite drive fault.
I cannot afford a DR company who would charge at least £300-£500.
I think the aussie guy is right and will try to do some more photos
as well as googling MOSFET choppers.

Thanks to you all,
Vic Pearson.

There are several MOSFET datasheets in these notes:
http://www.users.on.net/~fzabkar/HDD/HDD_ICs.txt

Here is a typical DC-DC converter using the Step - Down Buck Converter topology:
http://www.powerdesignersusa.com/InfoWe ... ntrol.html

Your MOSFET chopper is the Power Semiconductor Switch, the Pulse Width Modulation controller IC is built into the motor controller IC (SMOOTH), and D is the Schottky flywheel diode.

_________________
A backup a day keeps DR away.

Thanks for the info. from the aussie.
I have done some more shots of the board both of the
burnt out chip and the 3 main IC's used on the board.
Also included is a shot of the fuse,so I guess I will need
to find out what rating this is.
Also I have shot the other 6 pin 642 device used on the board
which has not been burnt out.
I hope this helps you if you are still inclined to pursue this.
Thanks.

I can't see the marking on the fuse, but I suspect it may be rated at 2A. The rating on the label should give you a clue. The following datasheet may help.

Littelfuse Surface Mount Fuses, N = 2A, S = 4A:
http://www.farnell.com/datasheets/48294.pdf

I would measure the resistance, on the 200 ohms range, of the 1A40 diode near the 4R7 coil. That should tell you whether that particular supply rail has a shorted load.

I'd also try to determine where the Samsung K4S641632N-LC60 SDRAM is getting its 3.3V supply. Test for continuity between either pin 1 or 27 (Vdd) of the SDRAM and the components in the vicinity of the two 642A MOSFETs.

See page 7 of the datasheet for the pinout diagram:
http://www.samsung.com/global/system/bu ... _rev11.pdf

_________________
A backup a day keeps DR away.