Seagate barracuda hard drive - Page 1
Forum section: electronics / repair

author: G7PSK
author_rank: Super Contributor
timestamp: August 23, 2014, 04:45:21 pm
content: 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

author: leppie
author_rank: Frequent Contributor
timestamp: August 23, 2014, 04:55:21 pm
content: BAT54 maybe?If you have a STM32 F4 discovery, you can source one from the SWD output (if you dont use it)

author: wraper
author_rank: Unknown
timestamp: August 23, 2014, 05:53:03 pm
content: 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.

author: DmitryL
author_rank: Regular Contributor
timestamp: August 23, 2014, 09:24:00 pm
content: Quote from: G7PSK on August 23, 2014, 04:45:21 pmYou 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 diedSurprisingly, HDD worked well after I desoldered blown TVS.Check the computer PSU, next time it may blow something else

author: leppie
author_rank: Frequent Contributor
timestamp: August 23, 2014, 09:37:09 pm
content: Quote from: wraper on August 23, 2014, 05:53:03 pmBAT54 is a schottky diode...

author: wraper
author_rank: Unknown
timestamp: August 23, 2014, 09:57:49 pm
content: Quote from: leppie on August 23, 2014, 09:37:09 pmYes, 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.

author: wraper
author_rank: Unknown
timestamp: August 23, 2014, 10:09:38 pm
content: here is a picture from the same PCB (also crappy)

author: G7PSK
author_rank: Super Contributor
timestamp: August 24, 2014, 08:33:06 am
content: 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.

author: wraper
author_rank: Unknown
timestamp: August 24, 2014, 08:47:46 am
content: 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.

author: free_electron
author_rank: Super Contributor
timestamp: August 24, 2014, 10:18:21 am
content: Thats the 5 volt rail TVS diode.

author: G7PSK
author_rank: Super Contributor
timestamp: August 24, 2014, 11:05:35 am
content: 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.

author: wraper
author_rank: Unknown
timestamp: August 24, 2014, 11:10:53 am
content: 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.

author: G7PSK
author_rank: Super Contributor
timestamp: August 24, 2014, 03:32:20 pm
content: 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.

author: leppie
author_rank: Frequent Contributor
timestamp: August 24, 2014, 07:21:26 pm
content: Quote from: wraper on August 23, 2014, 05:53:03 pmArghhh! I never did read "adjacent" in the OPSorry dude

author: SeanB
author_rank: Super Contributor
timestamp: August 24, 2014, 07:24:32 pm
content: I have a number of those drives, removed from old computers. They are good for replacing old IDE drives in dead obsolete computers.