TVS diode always goes short on Samsung

[helpless]

Hi again,
This HD103SI had a faulty TVS 12V diode, replaced, applied power, and it went short again.
Do not think I have a faulty PSU, as other drives behave normally.
What other components need checking for fault before deciding on PCB swap? Thank you.

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[shahij]

It's because of PSU or POWER CABLE CONNECTOR. Re-check

[helpless]

Thanks for your reply. FYI first short was not in my computer/PSU.
I use Maxtor, Seagate, Samsung, they are all satisfied with voltage. It's a 1 year old Corsair, shouldn't have any problems.
IMHO problem lies elsewhere.

[ShaneWard]

Might not be the new diod that is shorted, perhaps another component shorted too...

[michael chiklis]

Check if there are shorted capacitors, it can be also shorted motor chip SH6125B.

[fzabkar]

A TVS diode can only be damaged by an external fault. That's because it is connected directly across the supply. Therefore your PCB is not the problem.

Perhaps the breakdown voltage for your diode is slightly less than those used in other drives. Did you actually measure your PSU voltages? BTW, if your PSU has leaky or swollen capacitors, then this could result in overshoot at switch-on. A subsequent test with a multimeter, when the rails have settled down, may not show up the fault.

Take the cover off your PSU and inspect the capacitors. For numerous examples, see http://www.badcaps.net/forum/forumdisplay.php?f=32

[fzabkar]

Oops, I just had a closer look at your photo. You have installed the diode backwards.

[helpless]

Are you sure? The original diode was installed the same way, anode facing the power connector. And it looked as an original soldering.

[thatdellguy]

Picture:

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[helpless]

Well, at least I was far-sighted, bought 2 diodes.
Still don't understand, I can swear, the original diode was installed same way. And the soldering was done by my friend, who has been repairing televisions and monitors for 30 years. I may have been mistaken, but not him. Ok, I try the other way round and report back. I have nothing to lose. Thanks everyone, who helped.

[fzabkar]

Ask your friend what happens when you do this ...

+12V o---- |>| ----o Ground

;-)