Hello,

I am needing some confirmation on the TVS diodes and 0 ohm resistor locations. I have attached 2 pics, one marked.

Are red squares the TVS diodes here? If so, both read at 86 ohms.
Are the blue squares the 0 ohm resistors? If so, they both read open.

If need be, I know I can remove the diodes and bridge the resistor location, but what part numbers do I need to replace all these to safely use the drive again?

Hi,
The transils are SMA6F5.0A and SMA6F13A (available at farnell.com)
The fuses are 0603 4A

Mikippp

Measure the diodes in both directions. When you place the red probe on ground, you are forward biasing the Schottky rectifier that is in parallel with the TVS diode. This is responsible for the low reading.

_________________
A backup a day keeps DR away.

@Mikippp thank you for the numbers!

Hello fzabkar,

They do not read at all in the reverse direction(200 ohm setting) reading 123 on both, one direction with setting on diode. Are the blue squares the 0 ohm resistors? Are the part numbers OK that Mikippp referenced?

I forgot to mention in the original post that this drive does not spin up.

The blue squares are either fuses or zero-ohm resistors ("0" marking).

As for the TVS diodes, most HDD PCBs would use an SMA6F12A rather than the SMA6F13A. The difference is in the standoff voltage and breakdown voltage. Your Schottky and TVS diodes are testing OK.

https://www.vishay.com/docs/89458/sma6f5.pdf
https://en.wikipedia.org/wiki/Transient-voltage-suppression_diode

_________________
A backup a day keeps DR away.

Will these work for the 0 ohm resistors? https://www.digikey.com/en/products/det ... EA/5866925

Probably, but if you want to do the job properly, I would replace them with 2A and 4A fuses for the 5V and 12V supplies, respectively.

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A backup a day keeps DR away.

I am guessing they are the 0603 package size? It does not list them in Amps, just power (watts) and they do not list anything over 1/2 watt. I think you are saying to use smd fuses instead of 0 ohm resistors? Such as this: https://www.digikey.com/en/products/det ... -2/2563499

Yes, I would use smd fuses rather than zero-ohm links.

You would need to measure the package size for yourself. An accurate way to do this would be to scan the PCB with a CCD scanner (not CIS) and then count the pixels in an image editor.

_________________
A backup a day keeps DR away.

the TVS is forward biased too, which gives low (but not as low as a schottky) reading as well.
imo...

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Adatmentés - Data recovery

There was another thread where the OP performed the same measurements. The Vio supply rail had the same Schottky rectifier ("LS4") and we found that all 3 Schottky diodes produced the same reading (130 ohms). This meant that the contribution of the TVS diodes to the forward voltage drop was essentially nil, at least for that PCB.

_________________
A backup a day keeps DR away.

And you decided that it's a "TVS diode" problem?.... How clever....

OK, I'll add to the fluff....not everyone is born an Einstein.

deleted

_________________
A backup a day keeps DR away.

Working on the same board. Drive is from an external that had a 19V laptop power cord plugged in.

12V diode (red) is shorted. [diode check is 0.1 in both directions. resistance is 0.6 ohms in both directions.
12V fuse (blue) measuring 10k ohms = bad. This is an 0603.

I have not used fuses in smd designs. From what I can see the 5V fuse is marked S. The 12V fuse is marked with something like a C with a chip in the top surface? Are manufacturers consistent on markings for fuses? From the comments above I should expect the 12V rail to have a 4A fuse labeled S, but I have a C (0.2A)? Also from above, I should expect the 5V rail to have a 2A fuse which would be labeled N -- but I have an S (4A).

For reference, presumed good values on the 5V rail: the 5V fuse (marked S) is 0.6 ohms. The 5V diode is 1.445k, and 600 ohms initially in the inverse polarity. Diode check is 2V and 0.2V.

The fuse on the 12V rail should carry around 2A at startup. The 12V rail powers the spindle motor and voice coil. I believe the 5V supply typically delivers around 1A.

The two smaller diodes (in parallel with the TVS diodes) are Schottky rectifiers. I believe they are intended for reverse polarity protection. They would be responsible for the 0.2V reading.

_________________
A backup a day keeps DR away.