Will be doing 2x velociraptor 300gb PCB/u12 swap

I plugged my power supply cable wrong to my 2 velociraptors and killed both of the motor control chips on the PCBs of the hard drives. I’ve ordered 2 identical velos from eBay and will be doing a PCB + U12 chip swap with them when they arrive. Here are the pictures of the PCB showing a little damage on the smooth chips:

Do you guys think that this is the best way to go or is there a smarter/more efficient way of getting the data off of these drives?

Any comments are appreciated.

Yes, I believe that is your most expedient solution.

Be aware that the SMOOTH chip controls the onboard switchmode supplies, including the Vcore (1.2V ?), Vio (2.5V or 3.3V), and the negative supply for the read preamp inside the HDA. I suspect that U12 is powered from the Vio supply. Hopefully the damage was limited to the motor controller.

Good luck.

Hello and thank you Frank, I’ve read alot of your helpful posts over at HDDguru but chose to ignore those forums due to the data recovery naysayers.

I’ve several questions:

  1. I’ve bought a drive with the exact parameters - exact same MDL, DATE, DCM, LBA, COUNTRY, board number/rev etc, do I still need to swap the EEPROM from the old drive or should I just go ahead and swap the boards and try see if it works?

  2. Suppose I do so, is there any chance of damaging the new board or any part of the HDA? Suppose the preamp died as well, would that damage the new board?

  3. Is there a way to test if the preamp is faulty or it’s really a luck of the draw?

  4. Why didn’t the TVS diodes ‘save’ the motor chip?

Thanks so much for your help

Well I swapped the PCB, and the drive spins up now, but bios pauses for 10-20 seconds and still doesn’t recognize the hard drive. no seeking/clicking sounds at all…

I’m not a data recovery guy, not even an amateur, so I can only try to help you with very basic things. Please don’t accept the following statements as Gospel.

That said, I believe it is safe to swap WD and Seagate PCBs without transferring the EEPROM, but the DR professionals at HDD Guru warn against trying this on certain Samsung drives, IIRC. The EEPROM stores unique “adaptive” calibration data. If the tolerances between two drives are close, then a straight swap may work on some models, otherwise the drive will click, or power down, or identify itself with its internal family name.

You may like to refer to this thread for a more detailed explanation:

A dead preamp, particularly if it presents a short circuit across its supply rail, may also kill the associated DC-DC converter on the replacement board. You can test the preamp for shorts, but I don’t know of any other way to test it other than by powering it up.

I have often seen damage extend beyond the TVS diodes, so I am not surprised that this happened to you.

I see from your latest post that a board swap has failed, although the drive does spin up now. The next step is to transfer the EEPROM. If you are not adept at soldering, then your local TV/AV repair shop should be able to do it for you.

BTW, before you do anything else, I’ll try to help you test the preamp. There appear to be three DC-DC converters near the SMOOTH chip, each with its own inductor (L4, L1, L3). We need to do a little circuit tracing to find out which one connects to the 22-pin preamp pads at J1. If you can bear with me, I’ll compose another message with additional suggestions. I’ll also try to answer your PM.

Good luck, and keep cool.

Hello again and thanks for your detailed reply.

I’m planning to swap the ROM for the drive that spins up this weekend, and can see what happens from there. As for the drive that doesn’t spin up no matter what, it could be a preamp damage that somehow doesn’t let the drive boot up? What happens if we find out which DC converter sends power to the J1 contacts? Also is there a way to test the preamp pins to see if they’ve shorted? This way at least we can test to see if the U12 rom swap is worth doing to begin with

Photo of the pins:

I was thinking exactly the same thing. The heavier traces that lead to the preamp pads would probably be the power rails, plus two pads for the voice coil. The thinner traces would be the signal pins.

If we can determine which regulator powers the preamp, then a continuity check with a multimeter may be the easiest way to locate the power pins.

AIUI, the SMOOTH chip senses the onboard voltages. If any are out of spec, then the controller holds the Power_OK signal low. This keeps the MCU in a reset state. It could also be as you say, ie that the MCU refuses to spin up the drive if the preamp doesn’t communicate. If you are game, you could experiment with your new drive by masking off the signal traces at the preamp connector.

Here is the datasheet for an L7250 SMOOTH “5V & 12V SPINDLE AND VCM MOTORS DRIVER”:

It is not the same as your chip (L7251), but there are similarities.

Are you saying I should measure the on board currents while the harddrive is plugged in and running? Also, couldn’t I test the pins on the HDA of the two broken hard drives to see if there’s a difference? (in fact can test all 3 - the one that works, the one that spins up, the one that doesn’t spin up)

I would avoid live voltage measurements for the moment. But the HDA testing sounds OK. Just avoid the diode range on your multimeter. The DR guys at HDD Guru claim that you can damage your preamp on the diode/continuity range, but I suspect that’s FUD. If you are concerned, see the photos in the following thread:


How can I tell which of the pins are ground and 5v? Do I measure the paired contact pins or are they set up independently of each other? Do I have to trace the GND from the SATA connector to the HSA contacts to find which contact pin is GND?

If you haven’t already done so, I would set your DMM on the 200 ohms range and confirm the resistances of the TVS diodes at D3 and D4, and the adjacent zero-ohm resistors at R64 and R67.

As you say, you can use the SATA power connector as your reference point for circuit ground, and for the +5V and +12V rails.

Here is the pinout:

To identify the functions of each DC-DC converter, measure the resistances between each coil (L1, L3, L4) and ground. IIUC, the one that connects to ground will be part of the negative voltage supply for the preamp.

Another coil should connect to the Vio rail that supplies the SDRAM and EEPROM. Pin 8 of the EEPROM is the supply pin (Vcc).

M25P20VP, ST Microelectronics, 2 Mbit (256 K × 8), SPI, Serial Flash memory:

The remaining supply will be the Vcore (1.2V ?) for the MCU (WD70SC56). There should be continuity between the corresponding coil and several of the pins of the MCU.

I’m guessing that the two thin pairs of traces between the MCU and preamp are Tx/Rx differential pairs.

Two of the heavier traces would connect to the voice coil driver MOSFETs within the SMOOTH chip.

D3 is shorted both ways. This is the 5V diode?

D4 I’m not sure, it’s not infinite and it’s not 0 either (I don’t have a digital multimeter). I think it’s fine though, because in one way the resistance is > 100.

R64 and R67 are fine (0 OHMs).

I’ve actually measured these quite a while ago since I started researching about hard drives. The reason I didn’t mention them is because the SMOOTH motor chip has a burn mark/pin hole on it so I thought it doesn’t matter what the fuses do I still got to replace the PCP board. Thanks for the reply as usual.

D3 is the 5V TVS diode. IIUC, the +5V and +12V inputs were reversed, which is consistent with the damage.

If you are concerned about the spindle motor, you should measure the resistances of each of its three windings with respect to the common terminal. See the application circuits on pages 43 and 44 of the L7250 datasheet, and the block diagram on page 21.