Seagate barracuda hard drive

[G7PSK]

I have a seagate barracuda 7200 hard drive that I have removed from my mother in laws computer to replace with a larger unit.
Although it works there is what appears to be a blown diode on the board just above the sata power connection and next to an inductor. The one adjacent to it is labeled 54 40 google shows this a schottky diode, is this correct as the ones shown are all axial leads and I cannot find them as smd's.
Sorry about the photo quality I used my phone

[leppie]

BAT54 maybe?

If you have a STM32 F4 discovery, you can source one from the SWD output (if you dont use it)

[wraper]

No way it is BAT54. This is for power input protection from reverse polarity and maybe overvoltage. So it is either schottky or TVS diode.

[DmitryL]

I have a seagate barracuda 7200 hard drive that I have removed from my mother in laws computer to replace with a larger unit.
Although it works there is what appears to be a blown diode on the board just above the sata power connection and next to an inductor. The one adjacent to it is labeled 54 40 google shows this a schottky diode, is this correct as the ones shown are all axial leads and I cannot find them as smd's.
Sorry about the photo quality I used my phone

You might have taken a sharper picture... I've seen case like this. It was a blown TVS across HDD power connector.
I presumed that the cheap low-quality computer PSU started to generate high ripple voltage because of the capacitors degradation, TVS tries to cope with that and died Surprisingly, HDD worked well after I desoldered blown TVS.
Check the computer PSU, next time it may blow something else

[leppie]

No way it is BAT54. This is for power input protection from reverse polarity and maybe overvoltage. So it is either schottky or TVS diode.

BAT54 is a schottky diode... 

[wraper]

No way it is BAT54. This is for power input protection from reverse polarity and maybe overvoltage. So it is either schottky or TVS diode.

BAT54 is a schottky diode... 

Yes, but it is in completely different case and low current . And you need to be crazy to assume that someone have a spare  STM32 F4 to get a diode from it. Moreover there are 4 variants of BAT54 with different diode connections to pins.

[wraper]

here is a picture from the same PCB (also crappy)

[G7PSK]

The crazy thing is the hard drive still works despite the top having been blown right off the diode. I am uploading a better picture today.

[wraper]

There is nothing crazy. Pretty sure it is connected between power rail and GND. Therefore when it became open that did not affect working. You can just replace it with TVS diode with appropriate rating for the power rail where it is connected. +1 about that you need to check PSU.

[free_electron]

Thats the 5 volt rail TVS diode.

[G7PSK]

Thanks for all the reply's and advice. I checked the voltage on a known good power supply and found 5.18 volts across it when checked on the computers power supply it was 5.12 volts. I have ordered some 6 volt smd tvs diodes will that do.

[wraper]

Multimeter won't show the crap happening on the rail. You need either to use oscilloscope and measure under load or unscrew the PSU and check if there are not any bulging capacitors.

[G7PSK]

The scope shows just under 200mV peak to peak ripple. Took the power supply apart and could not see any bulging or leaking capacitors. Could be that it was a weak diode or there was some form of transient on the power input, I will try replacing the diode and see what happens the drive is expendable as its only a 40GB one I have flash sticks bigger than that.

[leppie]

No way it is BAT54.

Arghhh! I never did read "adjacent" in the OP  Sorry dude 

[SeanB]

I have a number of those drives, removed from old computers. They are good for replacing old IDE drives in dead obsolete computers.