HDD GURU FORUMS

Hello,

I have a hard disk [Maxtor Diamondmax 10 6L250S0) that was in a desktop whose power supply blew (loud bang, smell of burnt electronics). When the power supply was replaced, the PC would not boot at all. I started doing troubleshooting and as soon as I removed the SATA power cable from the hard disk the system powered on perfectly.

I checked the PCB on the hard disk and saw absolutely zero burn marks/blown/cracked components at all. Nevertheless, research on this great board makes me think that a TVS tripped (as it should have) and is now causing a short when plugged in. I've read that the TVS can be removed to see if it then powers up to allow for data to be retrieved (and perhaps later to replace the TVS to return to service as a junk drive - no essential data obviously)... but I have no idea what the two TVS in question (5V and 12V) look like on this particular board.

I'm attaching a photo of the board below and would appreciate if someone could point them out. Also, I have access to a multimeter but have no idea how to test the TVSes to see which one could be shorted open (which setting on multimeter, it has DC 5V/10V/25V/50V/100V, AC settings, resistance measurements, etc...) and where to probe. I tried to search for this information on the forum here but couldn't quite find the right info. Apologies if I'm missing something obvious.

Thanks!
Mike

Hi,

You can check the 2 big diode (CR501 and CR502) under the big white circle component (L500).
And you can check the similar diode on the left bottom on the photo, next to the power connector.

You can use the dmm with diode measuring function, and the good value is >100 on all direction for you.
You looking for short circuit, and maybe you have some on the pcb, you need to lift up the component, what you want to measure.

Maybe you need to check the 3.3V regulator also, and the FET on the right up on the photo.
If the short circuit still exists, you need to replace the VCD chip.

"Or find a pro is the better solution..."

Good luck,
Janos

Just a gut feeling, but I think your chances of success are good if you're careful. The fact the rest of the computer is undamaged is a good sign. The fact the computer won't start up with the power connected to the drive is also a good sign the TVS shorted. They don't always smoke, or look physically damaged. I suspect you'll find a short with a meter. While a diode check is usually how you would check a TVS (It's a type of diode), you could probably test it with an Ohms or continuity check, as it looks shorted. If it beeps on the continuity setting, or if Ohms reads close to 000, the TVS is likely bad. As mentioned, you'll need to lift one end of the TVS, or remove it completely, to determine that's the shorted part.

Thanks for all the great info.

I thought I would head back tonight to my parents (it's their computer and HDD, and I left it behind by accident) but the backup my Mom performed a couple of months ago restored successfully on their new drive. I'll get over there by Thursday because there's some recent info they'd like to get back if possible, and at least now I have a good idea how to check the TVSes and how to proceed.

Just to confirm, IIRC the CR201 and CR501 components were the same (large black components, 201 next to the power connector and 501 next to the L500 white round component), while CR502 looked slightly different. CR503 and CR504 were much smaller, but near to them on the board were diode symbols. I'm looking at primarily CR501/502 and maybe 201 as the culprits at this point, right?

This is all new to me even though I've been in IT [software support] for years, but I love new puzzles and challenges. Thanks again.