HDD from inside: Main parts

[Doomer]

Here we can discuss this article - http://hddscan.com/doc/HDD_from_inside.html

[ahmed_samy]

Hello Doomer,

it's very nice to meet you here - it's really a helpful article plus it's very simple .

I got a question why some WD HDDs come with a ransient Voltage Suppression diodes while some of the same WD models have not any of them on the PCB - I noticed that in many 80 and 160 GB ATA WD HDDs.

Best Regards

[Doomer]

I guess it would depend of place and time of manufacture
Because TVS diodes are not interfere with normal drive's behavior but only protect the device sometimes manufacturers do not solder them - to cut price

[ravi6662]

hi there. .. great site..

attached picture...

where would i find a TVS for this..
i can see the one on the 5v line.
but whats the component for the 12v line??

thanks

ps...
"Because TVS diodes are not interfere with normal drive's behavior but only protect the device sometimes manufacturers do not solder them - to cut price".....

does that mean i can remove the TVS, and my drive will spin up??

i can copy my data. and RMA it back to seagate!!.. warrentee till 2014..

[fzabkar]

You can remove the TVS diode, if you trust your PSU. A HDD will work quite happily without it, albeit without protection on the affected supply rail.

The 5V TVS can be substituted with an SMAJ5.0A unidirectional 400W diode, while the 12V TVS can be replaced with an SMBJ12A 600W unidirectional diode.

They can be purchased from Farnell, Digikey, Mouser.

Here are datasheets:

http://www.st.com/stonline/products/literature/ds/5616/smbj.pdf

http://www.st.com/stonline/products/literature/ds/5544/smaj.pdf

[fzabkar]

Here we can discuss this article - http://hddscan.com/doc/HDD_from_inside.html

Thank you for a very informative article.

Can you tell us where the temperature sensor is located?

Is it inside the preamp?

[Doomer]

Temperature of air inside HDA measured by read heads. Read elements can work as thermoresistors. Also there are at least two temperature sensors on PCB inside VCM controller and read channel. Temperature of HDA measured by read channel sensor (I think it's also used to calibrate read heads as thermoresistors on a factory, because each head has different resistance)

[fzabkar]

Temperature of air inside HDA measured by read heads.

I understand there is a heating element inside each head, for thermal flying height control. Furthermore, the write coil heats the head during writing. Then there are the occasional thermal asperities, etc.

This makes me wonder, what temperature are we actually detecting?

Recently, I was watching a thread at the Seagate forums where a particular HD reached 60 degC very soon after power up:

http://forums.seagate.com/stx/board/message?board.id=ata_drives&message.id=15916#M15916

What could cause this? IIRC, the SMART log showed 0 reallocated sectors and was otherwise clean.

FWIW, I found the following text strings inside the 7200.11 firmware update images. There are references to a "preamp temp", and to a thermistor.

Preamp temp %04X, %dd
Thermistor voltage %04X
Thermistor temp in degrees C %04X, %dd
VCM_TEMP
Temp Sensor Config
Thermistor Temp Sensor Offset
Thermistor Temp Sensor Scale
Thermistor Temp Table Elements
Thermistor Temp Lookup Table:
Temperature:
A to D Value:

[Doomer]

Preamp temp is the temperature measured by read heads
And thermistors temperatures are VCM controller temperature and Read Channel temperature

IDK what is wrong with this drive maybe it's bad sensor/calibration or maybe the drive is 60C or maybe it's glitch in FW
If temp sensor in Read channel was faulty when drive was calibrated on factory that would cause wrong calibration of heads measured temperature which would lead to wrong temp reports