Wd external HD power failure


I have a 500G WD hard drive WD5000H1u-00, I wrongfully plugged my laptop power supply (19 V) to hard drive, and did not realized it about 40 minutes or so, when connected the right power supply the blue light flashing and no access to the drive.

I did read some of the problem solving on this forum with the same power supply problem on possible damages of TVS Diode on the HD board,

so I did cut the D4 diode and tested it with millimeter and both ways there were no resistant ( 0 ohms), so the diode was dead, then I tested the hard drive without the Diode connected, fortunately my hard drive worked without any problem,

the diode on the board was marked LG 7BA and I did buy a replacement diode ( SMBJ12A), as was suggested on the board.

But the problem is,  I can not find the Cathode and Anode sign on the board,nor on the bad diode.

How can I connect the new diode when there is no sign of + or -?

1- Have anyone tried connecting the replacement diode successfully? 

2- is it safe to use the Hard Drive this way? ( without the D4 diode)

I just connected the hard drive to my laptop and did backed up some of my data and then disconnected it.

Appreciate your help on this.

The only person who might be able to help you is fzabkar. Try checking his posts or sending him a PM.


The cathode is the striped end of the diode. It should connect to the +12V pad. There should be continuity between this pad and pins 15, 14, and 13 of the SATA power connector.

The anode should connect to ground.

There is a diode symbol on the PCB in the following photo clip:

It is showing the anode on the left and the cathode on the right. If you set your multimeter on the diode test range, there will be a low reading (~0.600) in the forward direction, ie when the red probe is on the anode and the black probe is on the cathode. In the reverse direction the diode will be open circuit.

It is safe to run without the diode. However, your drive will no longer be protected from overvoltages.

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Thanks for the response;

sorry about the newbie question,

just to be sure and not to mistake any other sign on the board with diode related to D4,

is this direction that I have on the picture below correct?

appreciate your reply.


Yes, that’s correct.

Thanks a lot