Hello,

I've got a Seagate Momentus 5400.4 250 GB HDD which does not power up or make any sound.

I have read some of the excellent postings on HDDGURU regarding TVS diodes, but the pictures that other members have posted that I have used for reference, do not match my device.

Could someone please point out the TVS diode and fuse (if there is one!) from the picture that I have included.

Using the tracks from the power connector as a reference, the only component that I considered to be the diode is directly below pins 10,11 and 12 of the power connector.

However, the markings on this component reads 'W0AE', which when Googled, returns information regarding a Transistor (HCPL-817-W0AE).

Here is the link to the PCB of my device.

https://skydrive.live.com/embed?cid=F58 ... 8C2fjjaDBg

Any help would be greatly appreciated.

Thanks in advance.

Direct link to your photo ...
https://public.dm1.livefilestore.com/y2 ... JPG?psid=1

"AE" is the marking code for a 5V TVS diode.

_________________
A backup a day keeps DR away.

Thank you fzabcar.

I've just tested the diode (whilst it was still attached to the PCB) using the diode test feature of a multi-meter.

It reports:

.118 one way and .113 the other, I guess that this diode may actually be faulty then?

Thanks

It's probably OK. I normally recommend the 200 ohms range for testing the TVS diodes, since the diode test range produces a higher voltage that turns on the PN junctions of other devices connected to the same supply.

Does the +5V supply remain alive when powering the PCB? If so, then the diode is not the problem. Instead I would be measuring the voltages at the two coils. There is one near the semicircular cutout in your photo, and another adjacent to the motor terminals.

http://cdn.shopify.com/s/files/1/0207/3 ... 4.jpg?1931

_________________
A backup a day keeps DR away.

Thanks again fzabkar,

I'll pass this information onto someone else at work who is more capable than me with a multi-meter, I'll get back to you with the results.

Thanks you.

Fzabkar,

I could not find anyone who knew how to use a multi-meter, which supprised me!

So I followed the part from your your guide below 'To measure the voltage between two points'.

http://forums.seagate.com/t5/Barracuda- ... m-p/118908

I set the multi-meter to 2V DC and placed the black probe onto pin 5 of the SATA power connector, I then used the red probe to test the coils.

The coil nearest the 'cut-out' reported 0.002 and the other coil near the motor terminals 1.571.

Power was provied to the PCB during this test, so I would presume that at least, power is going beyond the TVS diode.

Any further suggestions?

I don't have a problem with conventional methods of data recovery, but anything to do with electronics is a massive learning curve for me!

Thanks again.

The coil near the motor terminals appears to be part of the Vcore supply for the MCU. The other one looks like it may be part of the Vio supply. Something is wrong there.

With power switched off, could you now measure the resistance between the Vio coil and ground. This will tell us if there is a short circuit on the Vio supply. Use the 200 ohms range of your meter.

_________________
A backup a day keeps DR away.

Ok,

I've tried that and the multi-meter displays '0L'.

I've also probed the TVS diode using the 200 Ohms range and here are the results:

126.9 one way, 121.0 the other way.

Thanks.

It does appear that there is something wrong in the Vio supply. Could you tell us the markings on the square 6-pin IC in that area?

_________________
A backup a day keeps DR away.

The nearest one I can see is 9 O'Clock from the coil (on my picture).

The markings are:

3049
0838B
MSC

Thanks again

Here is the part:

LX13049, Microsemi, PWM Buck regulator, 1.25A, 6-pin, marking 3049:
http://www.microsemi.com/document-porta ... -datasheet

Very carefully measure the voltage at each pin. Do not slip with your probes, as catastrophic damage may result. I suspect that this chip may be faulty, in which case it would probably be more expedient to replace the board.

_________________
A backup a day keeps DR away.

Black probe on pin 5 of sata power,

Multi-meter set to 2V DC

Power applied to PCB

looking at the chip as it is in my photograph, here are the readings:

0.02 <IC> Minus 0.01
0.02 <IC> Minus 0.04
0.01 <IC> Minus 0.01

The <IC> field represents where the chip is.

Thanks.

That's telling us that there is no +5V power getting to the IC. That's inconsistent with your measurement of +1.57V at the other coil. Are you measuring the voltage with the power applied?

Are you certain that the probes are making good contact? Sometimes the PCB is covered with a coat of lacquer.

_________________
A backup a day keeps DR away.

I thought it was on, but I've done it again:

0L <IC> .004
.003 <IC> .808
.003 <IC> .809

Do these readings make any more sense?

Thanks

The first (VPWR) and second (VCC) pins down the left side should both measure +5V. That's because they are wired directly to the +5V pins at the SATA power connector. Either there is a dry solder joint at the VCC pin, in which case just reflow it with your soldering iron, or you have measured incorrectly once again.

However, the more interesting result is the output voltage of 0.8V.

This is what you should be measuring:

5V <IC> Not/Connected
5V <IC> 3R3 coil -> +3.3V (?)
0V <IC> 0.8V (feedback resistors)

Can you measure the voltage at both sides of the 3R3 coil again? It should measure +3.3V (or perhaps +2.5V). If it measures 0.8V, then I expect that resistor R2 would be open circuit, in which case a repair should cost you only a few cents. However we would need to calculate its correct value.

_________________
A backup a day keeps DR away.

Fzabkar,

I've tested again using a different multimeter.

5.03 <IC> 3.43
5.03 <IC> 0.00
0.00 <IC> 0.80

I was supprised as the 3.43v (top right) value should not be connected and the middle pin should have been reporting the 3.43v value.

The coil reported 3.43v one side and 3.41v the other.

Thanks

Two of the pins are reversed (typos), but otherwise the voltages are as expected.

Sorry, that's about as far as we can go.

_________________
A backup a day keeps DR away.

Thanks for all of your help Fzabkar,

Although, I do have one more question, If I was to acquire a replacement PCB for this drive, is there a chip that contains adaptive information which would need to be transplanted on this model?

Thanks

If there are any adaptives, they would be stored in the 8-pin chip at about 10 o'clock to the LSI MCU, and above the screw hole, in the following photo:

http://cdn.shopify.com/s/files/1/0207/3 ... 4.jpg?1931

_________________
A backup a day keeps DR away.

Thanks very much, i'll give that a go.

It may take me a while to obtain a replacement PCB, but once I do i'll report back the outcome.

Cheers Fzabkar, you are a star.