Does this PCB have a TVS diode? (Toshiba 3T DT701ACA300) photo

jsflynn603 · Oct 30, 2017

I thought I dodged a bullet recently when one of my PSU's lit up like a Roman Candle but I have found that my 3T Toshiba HDD failed. Can someone please tell me if there is a TVS diode on the PCC (she photo) and tell me which one it is? Or is the drive too new to either have a TVS or perhaps it's too difficult to remove it in this never-ending world of miniaturization.

Snipergod87 · Oct 30, 2017

Are you trying to recover the data off the drive in question? While I have no idea what the diode would look like, but you often can get the PCB from the same model drive and install it and retrieve the data.

JaredDM · Oct 30, 2017

Snipergod87 :

You can't do that with Toshiba brand drives as they store all of the read/write head adaptives and service information in a ROM chip on the PCB itself. Non-native PCB will never work.

Actually, though, this specific model is a re-branded HGST drive sold as a Toshiba. However, these have a unique NVRAM code stored on the PCB which is also drive specific in most cases. So you can't just replace the PCB with another one and expect it'll work.

In actuality the only modern drives you can cold swap PCBs are Samsung drives, and not even all Samsung drives because some are actually rebranded Seagate drives.

JaredDM · Oct 30, 2017

Getting back to the OP's question. That PCB does have TVS diodes located where I've circled in red:

Test them both with a multimeter. A good TVS will read almost infinite resistance in one direction and a much lower resistance in the other direction (when you switch the red/black leads from the meter). A bad diode will read 0 or near 0 ohms in both directions.

If either one is blown, you can likely just remove it and it'll work long enough to copy out the data. Just don't continue to use it afterward as some of the overvoltage protection circuitry is now gone.

jsflynn603 · Oct 30, 2017

Thanks both. I know that I can't just flip out the PCB but my understanding is that I can if I remove the 8 legged chip and transfer that, correct?

However that won't be necessary, indeed, the inboard one (the one closest to the big square chip reads zero both ways, the other seems fine.

I know that you can buy replacement TVS diodes, if I cut out the old and replace I should be ready to go, yes? (assuming nothing else within the device was also dealt a death blow.

They are cheap meaning $0.40@ so postage and handling will cost more but there are many and there are no id #'s to tell which to replace it with.

See: https://community.wd.com/t/hdd-tvs-diode-faq/14692

Is that chip a flat bottom chip? Meaning if I use a soldering gun and as soon as I see melting I can lift the chip with tweezers and one end pops off the board, then repeat on the other end. Reversing that if I can find a comparable diode seems easy enough. (If I could find the right chip)

Any place that you know of where I can send the PCB to who will flip out the bad diode and install a good one, then I'll have a good working drive (as good as ever anyway) with protection still in it.

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Does this PCB have a TVS diode? (Toshiba 3T DT701ACA300) photo

jsflynn603

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Snipergod87

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JaredDM

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JaredDM

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jsflynn603

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