Repair of Plextor SSD PCB

[superrdan]

Hi, my Plextor 512 GB SSD recently failed to detect. Upon investigating further I located a fault on the PCB itself. The PCB is called a M6S-TSOP Rev:01, 68p38lcsm6s601x. The IC's labelled as U22, U23, U24, U25 and is a six legged device. On the device, it has the letters: aj3zk. Would be most greatly if anyone could assist with identifying this device or the PCB schematic. Thanks.

[nidlaX]

Hi, my Plextor 512 GB SSD recently failed to detect. Upon investigating further I located a fault on the PCB itself. The PCB is called a M6S-TSOP Rev:01, 68p38lcsm6s601x. The IC's labelled as U22, U23, U24, U25 and is a six legged device. On the device, it has the letters: aj3zk. Would be most greatly if anyone could assist with identifying this device or the PCB schematic. Thanks.

Please post a picture of the PCB. Although you can find pics of the M6S, it's always good practice to show us the exact board in question.

[superrdan]

Here is a link to the PCB images:

http://imgur.com/a/gFlkf

[jitter]

Hi, my Plextor 512 GB SSD recently failed to detect. Upon investigating further I located a fault on the PCB itself.

What is the fault?

The PCB is called a M6S-TSOP Rev:01, 68p38lcsm6s601x. The IC's labelled as U22, U23, U24, U25 and is a six legged device. On the device, it has the letters: aj3zk. Would be most greatly if anyone could assist with identifying this device or the PCB schematic. Thanks.

I strongly suspect they are step down regulators, but can't be more specific.
Edit: it looks like a DFN6 package. It's probably something similar to this.

[superrdan]

Your hunch on a step down regulator is consistent with the problem I see. Essentially the drive is not been detected. Not on an os, not in the bios and not in other pcs. It is a relatively new drive, and my aim is to recover the data on it. It would appear to be a power issue, as it is not detected at all. Will do some tests to see if the ground,power and signal pins match the pins on that step down regulator.

[wraper]

It would appear to be a power issue, as it is not detected at all.

Completely irrelevant. Not detecting the drive can be caused by almost any sort of fault.

[superrdan]

It would appear to be a power issue, as it is not detected at all.

Completely irrelevant. Not detecting the drive can be caused by almost any sort of fault.

Yes, but where would you start debugging? The sudden stop and not gradual intermittent failure suggests something sudden. Plus the suspicious look of of an IC that would appear to be located around the general power area of the PCB leads me to believe that it may be a power failure. If say one of the flash IC's stopped working and the controller was still functional, I would think the power is fine. Also I should add, when powered on, the seems to be heat build up in the area of said IC.

[wraper]

Yes, but where would you start debugging? The sudden stop and not gradual intermittent failure suggests something sudden.

Take the multimeter and measure actual voltages?

[superrdan]

Measuring is definitely a good idea. Thats why I asked for a possible schematic, to find some test points. I believe most SSD's have 5V supplied to them and then regulate down to 3.3V, 1.8V and 1.2V. Checking some of the other chips, I can find the 3.3 V. Still hunting for test points for the rest.

[wraper]

Almost all of the ceramic capacitors are for decoupling. Just measure the voltages on them. Your chances to find the schematic are not higher than winning $10000 in lottery.

[superrdan]

The SSD also used Marvell® 88SS9187 controller by the way. Measuring across the caps, I find a 5V, 3.3V and 1.8V. I cannot find a 1.2 V but not conclusively say ifs its missing or present.

[jitter]

Marvell isn't exactly known to publish datasheets freely, so I can't even find out what voltage it's running on.

The suggestion to measure across ceramics was a good one, but not all ceramics may be for decoupling of power lines.
Locating the step down regulators is the easy bit, and typically, their output will be through an inductor close by. I would probably measure on the inductors with respect to ground to see if the step down regulators are all working. I agree with one of Dave's laws: "though shalt measure voltages".

So, the first step is to make sure that all step down regs are outputting what seem to be logical voltages by measuring at the outputs of all regs (or rather behind the inductors).

Having said that, a dodgy looking IC may be an indication, especially if there's a heat build up that seems higher than normal. But be aware that a reg that's running hot may not be faulty, but running hot because something further down the line draws too much current.

[superrdan]

Thanks jitter and wrapper. You are really providing very insightful advice. I will do as suggested as measure each regulator. The good news is that there is another regulator like this on the board that I can measure as a reference. I notice some inductors nearby and will do some tracing to pair the correct inductor to the regulator prior to measuring.

On the suspected faulty regulator, it is very likely that is was something downstream that either failed or drew more current perhaps due to heat. This may of raised the temperature threshold or current draw on the rail. I notice a slight burn on pin 5 of that IC, likely the output. It then runs to a via and there is an inductor close by on the other side of the board.

An interesting note, this drive comes from a slim high performance ultrabook type laptop. Mostly used for light workloads but sometimes runs FPGA builds and Matlab sims.

Will report back once I have made these measurments.

[superrdan]

I can confirm that the suspect regulator is in fact faulty.

I first measured a working regulator (same part number) and confirmed that pin 5 is the input at 5 V and pin 1 is likely the output at 1.5 V (it routes to an inductor).

I repeated the measurement on the suspect regulator, the input is present at 5 V but the output is 0 V. Ok having now confirmed that this IC is blown and is a regulator that takes a 5 V down to 1.5 V, any suggestions as to how to proceed to either repair or at least it get powered in a temporary state to copy the data of it.

[Monkeh]

That doesn't confirm the IC is blown, simply that it's not running.

Have you investigated WHY it's not running?

[jitter]

I can confirm that the suspect regulator is in fact faulty.

I first measured a working regulator (same part number) and confirmed that pin 5 is the input at 5 V and pin 1 is likely the output at 1.5 V (it routes to an inductor).

I repeated the measurement on the suspect regulator, the input is present at 5 V but the output is 0 V. Ok having now confirmed that this IC is blown and is a regulator that takes a 5 V down to 1.5 V, any suggestions as to how to proceed to either repair or at least it get powered in a temporary state to copy the data of it.

Good, you narrowed it down to a voltage rail but I agree with Monkeh that no output doesn't necessarily mean it's broken. Usually regulators can withstand certain fault conditions for indefinite amounts of time because of built in protection circuitry.

Now it's time to find out if it's indeed broken, or shutting down because of overcurrent.

What I might do is remove the inductor to disconnect the output from the rest of the circuit and feed in the correct voltage from a lab power supply with a lowish current limit. The other rails are powered the normal way. If the SSD works normally, then copy the files from it. The drive may even turn out to be repairable later.
If it doesn't work and current drawn from the lab supply is excessive, the fault was not with the regulator but further down the line. If that's the case, salvaging data from the SSD might not be possible.

[superrdan]

I can confirm that the suspect regulator is in fact faulty.

I first measured a working regulator (same part number) and confirmed that pin 5 is the input at 5 V and pin 1 is likely the output at 1.5 V (it routes to an inductor).

I repeated the measurement on the suspect regulator, the input is present at 5 V but the output is 0 V. Ok having now confirmed that this IC is blown and is a regulator that takes a 5 V down to 1.5 V, any suggestions as to how to proceed to either repair or at least it get powered in a temporary state to copy the data of it.

Good, you narrowed it down to a voltage rail but I agree with Monkeh that no output doesn't necessarily mean it's broken. Usually regulators can withstand certain fault conditions for indefinite amounts of time because of built in protection circuitry.

Now it's time to find out if it's indeed broken, or shutting down because of overcurrent.

What I might do is remove the inductor to disconnect the output from the rest of the circuit and feed in the correct voltage from a lab power supply with a low current limit. The other rails are powered the normal way. If the SSD works normally, then copy the files from it. The drive may even turn out to be repairable later.
If it doesn't work and current drawn from the lab supply is excessive, the fault was not with the regulator but further down the line. If that's the case, salvaging data from the SSD might not be possible.

Agreed, so best case is that it is indeed that regulator. I will do as suggested, remove the inductor, and solder a test wire to a lab power supply. That may at least allow me to retrieve the data (my primary concern). What current do you suggest I start with as a limit, 1A perhaps?

[jitter]

Hard to say. I might start at 500 mA and see if the lab supply goes into CC mode. If so, I might turn it up a notch to 1 A and try again. If still no luck, 1.5 A, but anything above that and I think it was toast already.

[wraper]

I would not recommend supplying 1.5V right away. There seem to be 2 resistors connected to the feedback pin for setting the output voltage. Measure resistor values for both ICs, if their values are the same for both ICs, then you can assume there should be 1.5V. If their values are different, output voltages should be different too.

[janoc]

Also some of these regulators have enable/inhibit pins.

Lot of these complex boards have very specific power sequencing needs - so check whether or not that regulator is actually enabled! It may not be and by applying power from a lab PSU you could blow the board for good.

[superrdan]

Good points,

I got abit over excited and trigger happy. Prior to powering on, I should check if there is a power sequencer and if it is indeed 1.5 V. The "aj" on the buck converter also suggests it is adjustable and set via external resistors. It might prove quite tricky to get the power sequence right if using a lab supply. Will give it a bash when I am back at work and have better equipment.

[jitter]

Getting the voltage right is essential, but the timing may not be that much of a problem. With a 6-pin package, there's likely only going to be an Enable pin, but not a PWR_OK signal back to the sequencer. Perhaps that's also why it looks dodgy, it might have burnt up because there was nothing to detect the fault and it wasn't shut down as a result.

I might try powering the labsupply first and then the rest. Worst case would be to have to power the labsupply exactly in sync with when the Enable is applied.

[superrdan]

Ok great stuff, I managed to make some progress:

For starters, each of these regulators has an output inductor and a resistor divider network that determines the regulated voltage.

As I do not exactly know the part number, I have had to measure and compare to the other working regulator on the board.

The output voltage is set probably by a formula such as:

V out = V fb * ((R1+R2)/R2)

On the working regulator, R1 and R1 are 11k ohm. The output voltage was measured to be 1.5 V.

On the broken regulator, R1 is 26k ohm and R2 is 13.6k ohm.

Back calculating Vfb from the working regulator puts it around 0.75 V.

Applying this formula to the broken regulator results in a speculated value of 2.4 V (this is surprising, I expected 1.2 V, maybe I have the resistors mixed).

For reference, if anyone ever encounters this problem, here are the connections (the components are connected through vias in some cases):
U23 -> L3 -> R62 -> R65
U24 -> L4 -> R67 -> R68

I then removed the output inductor L4, and powered up the board, I confirmed that the regulator still does not produce an output voltage (not surprising as I removed the inductor). I also checked other inductors on the board, 1.5 V, 1.8 V, 3.3 V and 5V are all present.

I guess the next step is to connect a lab supply in there. Even though the calculations show that it could be 2.4 V, I will rather start with a lower voltage at 1.2 V for testing and then only go higher if it still doesn't work.

Thanks everyone for giving me a fighting chance 

[Monkeh]

The next step would be to confirm there's no short on the rail you're wanting to power..

[superrdan]

 

Sorted, soldered a test lead into the removed inductor and powered at 1.2 V. The current drawn is 0.6 A. Connected this supply first and then the SATA connector and power. Drive took around 10-20 seconds and then bingo, detected in my windows PC.

I was able to recover all of my critical data. My main objective is now complete. I may still try and repair the drive fully as a hobby, but will not really ever use it for anything important or critical.

Thanks all for your assistance! I would be nowhere close to retrieving my data without you!