Assistance identifying TVS diode

[Nick_CT]

Hi, please help me identify which is/are the TVS diode/s on this PCB. It's a WD800JD-00JRA0 and it won't power up. Note the PCB has both SATA and MOLEX power connections. I assume both connections will have TVS diodes in place to protect the board? I've searched other threads and TVS diodes seem to look different on each board. If I check it/them on a multimeter on 200k what should the reading be?

Thanks in advance.

SATA connection:




MOLEX connection:

[Cleanroom]

Get a matching board and swap U12. Match the etched number on the board. Should start with 2060

[cheadledatarecovery]

Older WD drives do not have the component you are looking for. Most power surges knock out the motor controller chip.

[Nick_CT]

I was hoping it would be a simpler matter of removing the busted TVS than swapping board and U12.

Is there a way/criteria for identifying TVS's? Are they labeled with a D on the board? It's difficult for me at this stage to identify which boards have them and which don't.

[fzabkar]

Is there a way/criteria for identifying TVS's? Are they labeled with a D on the board?

On those boards where the components are labelled with circuit references, a diode will usually be identified as Dnn. However, some designers use the CRnn designation although I usually see this on older boards, and usually for rectifier diodes.

A TVS diode works by clamping voltage spikes. Therefore it will be connected directly across a supply rail, sometimes with a series inductor or fuse. The anode of the diode goes to ground, while the cathode (striped end) connects to the positive supply rail. They will usually be located near the power connector, but not always.

My notes may help you identify them via their marking codes:
http://www.users.on.net/~fzabkar/HDD/TVS_diodes.txt
http://www.users.on.net/~fzabkar/HDD/HDD_ICs.txt

TVS diodes in HD applications are usually (always?) unidirectional, meaning that they behave like a forward biased diode in one direction, and a high speed zener clamp in the reverse direction.

A diode test at the power inputs may be able to identify the existence of TVS diodes.

[poehere]

Older WD drives do not have the component you are looking for. Most power surges knock out the motor controller chip.

I am sorry but I think you are not reading and understand what we just told you on this one

Older WD drives do not have the component you are looking for. Most power surges knock out the motor controller chip.

Get a matching board and swap U12. Match the etched number on the board. Should start with 2060

Read this carefully and follow the advise here on this one. You can get your Local compter store or even your local TV repair shop to move this one for you if you wish and are not skilled at solidering. Frank will say it is cheap to do this one.

[Nick_CT]

Thanks fzabkar for answering my question, that's all I was after. Ta.

[Nick_CT]

As a follow up to this I thought let me have a look at a different drive and see if there are TVS present. This is a WD160 manufactured in June 2010. I've circled what I assume are the TVS's. Am I correct?

[fzabkar]

I've circled what I assume are the TVS's. Am I correct?

Spot on.