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 Post subject: need help in 2.5"hdd of hitachi
PostPosted: August 2nd, 2019, 8:04 
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Joined: August 2nd, 2019, 7:23
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Location: EastAsia
it sudden dead with no power.
before that it does suddenly turn off my computer when it is connect, then I turn it on again, it seem no problem, but after that it sudden turn off when using, and can not detect by bios ever again.
I have read some post that it may be the problem of tvs diodes, and the resistance between is about 30ohm ?
so I remove it but after that I measure the resistance, it is still near 0 ohm, it seem to be grounded in the whole +5V rail,
I would like to ask is this normal? and why there are 2 tvs diodes connected in parallel ?

(the red area and green area is ground, after I remove all 2 tvs and 2 cap)


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 Post subject: Re: need help in 2.5"hdd of hitachi
PostPosted: August 2nd, 2019, 8:36 
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could anyone can suggest some testing point, so that I can test it?


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 Post subject: Re: need help in 2.5"hdd of hitachi
PostPosted: August 2nd, 2019, 12:42 
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When you power on the drive is there any sound at all. ie can you hear a soft beeping sound coming from the drive.

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 Post subject: Re: need help in 2.5"hdd of hitachi
PostPosted: August 2nd, 2019, 14:03 
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Fuse at F1 is “open” (I.e. no continuity)?

Should be closed (I.e. continuity meter should “beep”)

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 Post subject: Re: need help in 2.5"hdd of hitachi
PostPosted: August 3rd, 2019, 2:59 
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How do the diodes measure out of circuit?

If the two fuses are open, and the diodes are OK, then I would be looking at the motor controller IC.

As for your question regarding the parallel diodes, one is a TVS diode for overvoltage clamping, while the other is a Schottky rectifier for reverse polarity protection.

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 Post subject: Re: need help in 2.5"hdd of hitachi
PostPosted: August 3rd, 2019, 8:15 
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Joined: August 2nd, 2019, 7:23
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Thank you so much for all of you replies.
for Q1, When you power on the drive is there any sound at all. ie can you hear a soft beeping sound coming from the drive
no , ther are no spin and no power.
for Q2, Fuse at F2 is “open” (I.e. no continuity)?
yes, may be F2 burned so that it is open, infinite resistance; I did not bridged it yet, because it seem to be toasted the board if the green and red area is still grounded. ( 0 ohm between them, after I remove all the component 2 cap and 2 diodes.)
and besides fuse F1 is shorted (normal)
for Q3 yes after I remove the TVS diodes, I measure them offline, It is about 900 ohm, which mean it is normal

And I would like to ask why green zone is grounded?
And I found some strange thing, for my common sense cap should not have 0 ohm resitance in DC; but in point A, B, C it show 0 ohm, is this normal?
And I can not find correct TLS2505 motor ic pinout, it seem quit different in google search compare to the board, is ther are many different vers?
And if I swap the board, did I need to swap (bios & nvram), or just nvram?


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 Post subject: Re: need help in 2.5"hdd of hitachi
PostPosted: August 3rd, 2019, 13:15 
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If you are lucky, there may be a shorted bypass capacitor across the +5V supply. Otherwise the motor controller is most probably bad.

As for pinouts, I have not seen any datasheets for motor controllers since around the time of the L7250 SMOOTH IC. I suspect that many ICs are custom designs.

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 Post subject: Re: need help in 2.5"hdd of hitachi
PostPosted: August 4th, 2019, 7:25 
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Thank you for your replies.
the 2 bypass capacitors is normal after measured off circuit, may be the motor controller is dead


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 Post subject: Re: need help in 2.5"hdd of hitachi
PostPosted: August 15th, 2019, 8:59 
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I would like to ask that what is the common value of the resistance to ground of the capacitor D which near the inductor,
the value now is forward 49 ohm and reverse 80 ohm , is it relatively low? thanks


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