My Book 500 GB - Used Wrong A/C Adapter - How to Remove D4 Diode?


I used a 19V laptop A/C adapter on a My Book 500 GB, and it started blinking nonstop with an audible clicking. It continued to blink when I used a USB connector, and the blinking stopped when I used FireWire, but the drive would not power on.

After trolling this board, I have deduced that I tripped the 12V safeguard when I used the 19V adaptor. I have read that the D4 diode is the likely culprit, but I’ve never tinkered around with diodes and Torx screws before, so I wanted to put a picture up here before I do anything too drastic. Many thanks in advance to this community for any assistance you can provide.


Look for the posts by fzabkar he is the only who really understands this area. Many of those posts have Pics attached. He’s helped a few people who hav e done the same thing.


TVS diodes D4 and D3 are commonly found near the SATA power connector in WD’s 3.5" drives. Your photo is of the bridge board inside the enclosure. I suspect that D4, D18, and U9 may be involved with the power supply, but I can’t see their markings or their circuit connections.

Have you tried connecting the drive directly to the SATA controller of a computer motherboard? If it shuts down the supply, then upload a photo of the component side of the drive’s PCB.

Hey there, fzabkar! Thanks for checking in with me.

I do not have the equipment for connecting the SATA controller directly to a motherboard. I can see D4, D18 and U9 pretty clearly… I’m attaching a couple other photos here, hopefully one of them will clear things up. Here’s the first, in which I flipped the bridge board over to reveal the other side. Power supply in the lower left corner, the D4 and D18 diode pairs are by the barcoded silver sticker on the left:


And here’s the second photo, of the board on the drive itself:


Again, I’m a total dunce at all this, I hope this gives you the information you’re looking for. Thanks again, fzabkar!

You need to remove the hard drive’s PCB. On the other side you will see D4, D5, R67, and R64 near the SATA power connector. D4 and R64 would be the most likely suspects. Inspect them for visible damage. Measure their resistances on the 200 ohms range of your multimeter. If you don’t have one, a cheap digital multimeter should cost you US$10.

Hello again! I’ve taken the PCB off, but I can’t see any visible damage, and when I test the resistances of D4 D5 R67 and R64 with the multimeter, the result always seems to be the same no matter where I put the needles: a momentary spike to anywhere between 10 and 30, then a quick plummet to anywhere between 1 and 3, eventually winding down to 0. Here’s what I’m looking at:


Are you measuring the resistances on the 200 ohms range of your meter, with power disconnected from the board?

There is a burn mark on the insulation sheet. Remove the sheet and upload a new photo.