I've been lurking around here for the past couple of weeks. I posted over at a different thread in regarding the TVS chips on the Seagate boards.


won-start-with-seagate-hdd-connected-t12678.html

I uploaded a few views of my board (First few were huge in file size so I trimmed them down; hope the quality is adequate)

I suspect the SMOOTH Chip might be the problem. The drive is not powering up at all. My untrained eye doesn't see other anomolies on the board.

Willing to do a PCB swap and move the EEPROM chip from the patient to the donor. With your help, I need to verify which components failed.

So far, I've metered the TVS diodes on a multimeter and the mV values I get for them are good: 481mV and 527 mV.

hi,
please connect power and check this 3 pins voltage.(sometimes need connect with hard drive too).
can and you heard sounds like it?(closeup hard drive and listen carefully)

_________________
data recovery service[/b]

You asked which components failed. Generally when you troubleshoot an MCU based circuit, you check the power supplies, oscillator, and reset pin.

So in addition to the SMOOTH chip, you could measure the voltages at the load side of each of the inductors in the onboard switchmode supplies.

There is a 2R2 inductor at the top RH corner of the SEAGATE MCU. Carefully measure the voltage between the top LH corner of the inductor and ground.

Also measure the voltage between ground and the bottom LH corner of the 4R7 inductor above the MCU.

Then measure the voltage between ground and the bottom LH corner of the 4R7 inductor at the LH side of the SMOOTH motor controller.

I suspect that the M78AQ / L119B chip below the SMOOTH chip may be a linear regulator, but I'm not sure.

FYI, the EEPROM chip is located at the bottom RH corner.

M25P40VP, ST Microelectronics, 4 Mbit (512 K × 8) Serial Flash memory:
http://www.datasheetcatalog.org/datashe ... Xyuxsz.pdf
http://www.farnell.com/datasheets/40267.pdf

Here is the datasheet for the chip above the middle 4R7 inductor.

uPA2680T1E, NEC, MOSFET WITH SCHOTTKY BARRIER DIODE, marking A2680, 6-pin:
http://www.datasheetarchive.com/pdf-dat ... 436380.pdf

I need some time to do some research; looks like a steep learning curve here for me. Hopefully this thread won't go stale on me.

I will measure the suggested components. Question: can I backprobe these and make meaningful measurements? It was suggested to assemble and power up the drive and therefore the components are facedown toward the HDA.

I'm not a DR guy, but I expect that the power supplies should be present if you test the board on its own, without it being mounted on the HDA.

1st inductor (2R2) - 1.115 V to ground
2nd Inductor (4R7 - above MCU) - bogus readings basically 0V
3rd Inductor (4R7 - below EEPROM) 0V

As for the 3 pin power connector to the spindle - no voltage readings and the spindle is dead quiet. Nothing is happening when fully assembled.

Will look for specs on the inductors. Thanks for you directions so far.

ISTM that you have confirmed that the SMOOTH chip is faulty. I'm assuming that the 12V supply is getting to the chip.

I have only found one datasheet for a SMOOTH controller:

L7250 5V & 12V SPINDLE & VCM MOTORS DRIVER:

http://www.datasheetcatalog.org/datashe ... Xyuswx.pdf

The L7250 is an early design. I don't how the current versions compare. Certainly the pinouts are different. I suspect that nowadays the SMOOTH controllers are custom designed.

The application circuit for the L7250 shows that it is responsible for three voltage regulators -- +1.8V, +3.3V, and -4V. The latter probably feeds the preamp inside the HDA.

I suspect that the two 4R7 inductors are part of two switchmode supplies that are under the control of your SMOOTH chip. The fact that you are measuring 0V would suggest that the chip is dead. Either that, or there is a short on one of the loads. The chip also looks a bit discoloured.

I don't know which core is used by the Seagate MCU, but if it is an ARM9, then the 1.15V regulator is consistent with a 1.2-V core voltage. Typical I/O voltages are 3-V and 1.8-V.

BTW, don't worry about the inductors. They are usually more robust than the surrounding active components.

As the number of faulty components seem to increase with my troubleshooting, the solution of ordering the same drive and using its PCB as a donor appeals to me. With my scant experience soldering microcomponents, changing out a smooth chip would take me too long. With the 64 pins and tight space I visualize myself soldering and unsoldering the pinouts because of where I am on the learning curve. Luckily, I might have access to a facility that can make these small solders a bit more managable (ie magnifying lenses, proper sized soldering tools, contamination control...etc) I think even changing out the EEPROM from patient to donor will stretch me.

I am tempeted to find a donor. I can continue troubleshooting and changing out components on the patient once the data is out.

I am assuming that you know for sure that the circuit board isn't receiving power?

This drives have widespread failure with the Bearings, which can to some seem like PCB issue, but power will clearly be flowing if checked.


Also; on these drives if the PCB is at fault...the easiest course of action is to just replace the PCB and transfer the EEPROM. Saves a lot of time.

That is the most expedient solution. All the rest has been an intellectual exercise.

Ultimately, I am not giving up on the board. Where I am sitting on the learning curve, I know just enough to be dangerous. Not a good combo for the drive: ambition and inexperience! I assume the components on the HDA are good thus far. Just need to put the PCB in order first. I'm almost positive that means changing out components on it before I get to the HDA. So I will eventually need some guidance down the road.

Currently, the biggest hurdle is appropriate bench equipment. I have access to tools superior to what I own. Unfortunately they're offsite and means extra time which is unavailable right now. Last set of of probing (24 hrs prior to this post), I caused some arcing (short-circuiting) trying to get V readings from the SMOOTH Chip. Pins were just too damned small for my probes - my eyesight is a little on the dim side. So I temporarily stopped troubleshooting.

All I know so far is that I have good voltage at the TVS diodes and need to re-follow the traces. I assumed one of them was going to the SMOOTH Chip but I am second-guessing myself right now. A magnifying lens is in order here & some better voltage testing equipment. I used an oscilliscope before and remember delicate probe clamps that might be appropriate and will show an irregular signal too (if it's relevant)

I just worry this thread will go stale by the time I gain any insight. Would it be appropriate to add these to the thread here if too much time elapses (weeks/months?) Never expereinced my prior threads on any message board go this long without closure. Suggestions? BTW, thanks y'all! Appreciate your enthusiasm and knowledge.

I purchased a new drive with similar specs. The drive powered up and spindle is operational. Powered down and all is good. No unusual noises...etc. Next step will be to move EEPROM from donor to patient. Let u know how that turns out within next seven days.