Repairing Hard Drive Logic Boards

Hard drives have been the gold standard in storage medium for a very long time. However, that isn’t to say they are without faults or are not susceptible to damage or data loss. When these drives do fail, and if there are no available backups, this can come with grave consequences. This is especially true when the drive is of great evidentiary value or contain many hours of work product. Either way, shrugging your shoulders over the loss is not always acceptable. There are a number of potential factors that could have caused the drive failure. In this blog post, we will take a look at the easiest and least invasive repair we could attempt – swapping the drive PCB.

Getting Started

Before you get started, you should unscrew the logic board from the damaged drive and inspect it. There may be visible signs of damage that could clue you in on the issue. Components with bulges, scorch marks, or melted plastic are good indicators of damage. However, you may not always see visible damage on the drive itself. That said, swapping PCBs is straightforward and does not require a clean room because we will not need to open the drive and expose the platters. Therefore, it is worthwhile attempting the repair first prior to moving onto more difficult repairs (like swapping the drive’s read/write heads).

With the PCB removed, we need to review the board for two pieces of information. First, identify the PCB revision number, which should be printed on the edge of the board (here are some examples). Secondly, identify the 8-pin ROM chip on the PCB. The ROM chip, which contains unique drive geometry and firmware data for that specific drive, must be swapped onto the PCB board from the donor drive. If you do not swap over this chip the repair will be unsuccessful.

There may be a few 8-pin chips on the board, search the component number on the face of each chip online to identify the ROM chip. If there is any confusion, one could swap over all of the 8-pin chips – although if any of these chips is causing the problem you will see that issue carried over onto the donor board. Some drives may not have a separate 8-pin ROM chip and its function may be integrated into a separate chip or controller. Our example will assume this hypothetical repair drive contains a free standing 8-pin ROM chip (as is often the case). Lastly, make sure to photograph the orientation of the 8-pin ROM chip prior to removing it from the damaged PCB.

Lastly, make sure to photograph the orientation of the 8-pin ROM chip prior to removing it from the damaged PCB. These chips must be placed in the correct orientation on the donor board. Failing to do so can damage the ROM chip itself, and if that data is permanently lost, will make any attempted repair futile. For that reason, it is recommended to use a chip reader and preserve the ROM chip data in case the chip is damaged in the repair process.

Picking the Donor

After the damaged drive has been inspected and photographed, it is time to find a suitable donor drive online. There are a couple ways to go about this. If you are only interested in attempting the PCB repair itself, you can buy standalone PCBs from various online retailers for the same drive make, model, and board revision number as the damaged drive. However, I would recommend buying a near match donor drive from eBay or Amazon. The reason I recommend that, is that by picking the correct donor drive, you can go straight from the PCB repair to attempting other more complicated repairs, like swapping the read / write heads or the drive motor, in cases where you are not sure what needs to be replaced on the drive.

In general, when looking for good donor drives, you want to match on the following items: Model, Part Number, Firmware Version, Production Date, and Site Code. Using an online retailer like eBay or Amazon is helpful because there will typically be pictures of the front label where you can find this information. Additionally, you can ask the retailer to identify these values as well as the PCB board revision number which may not be captured in the listing photos. I have found this guide to be a particularly helpful reference when identifying suitable donor drives. In the two photos below, see an example of the board revision number printed on a PCB and the 8-pin Winbond ROM chip, respectively.

Performing the Swap

As mentioned previously, performing the swap itself is relatively straightforward and should not take more than 20 minutes of your time. In some ways, inspecting, researching and documenting the board and finding the correct donor drive takes more time than the actual repair itself. It isn’t as easy as unscrewing the PCB from the donor and screwing it onto the damaged drive. As we discussed, this would fail because the damaged drive’s 8-pin ROM chip would not be transferred over onto the replacement PCB. So let’s discuss how that process works — it’s very simple.

Prior to removing the ROM chip, you can attempt to read the chip using a chip reader and an 8-pin SOIC clip. You may need to read the chip multiple times as doing this while it is on the board can give you bad readings. If you find you are not getting the same read reliably enough, you may have to perform an additional read once the chip is removed from the board and there is no other electrical interference to be had. Store this preserved data like you would any other evidence as you may need to write it back to a replacement ROM chip if the damaged drive’s ROM chip is damaged during the repair process.

Before removing PCBs, make sure to distinguish between the damaged and donor drive PCBs so that you do not mix them up accidentally. Additionally, ensure you are aware of the correct orientation of each 8-pin ROM chip and which board it originally belonged to. Now, we will need to remove the ROM chips from each board either using hot air or IR. Raising the chip to around 200-220°C in about 10 seconds should allow you to remove it without any resistance. Using a pair of tweezers can help feel out when the chip is ready to go. Do not attempt to remove the chip if there is any resistance at all. It will readily come off when the solder has reflowed. You can apply flux to the leads to promote solder reflow.

Once you have removed the ROM chips from the damaged and donor drive, you can now swap the damaged drive ROM chip onto the donor drive PCB. The donor drive’s ROM chip can be stored elsewhere for now as it will likely not be needed from here on out (unless you want to place it back on the donor drive PCB if the repair is unsuccessful). Before you swap the damaged drive ROM chip, use a soldering wick and clean up the pads on the donor drive so that they are level.

There are two ways to get the damaged drive ROM chip onto the donor drive. If you’d like to keep the heat down and do it the slow way, you can manually solder each of the 8 pins onto the donor board. This is a little bit safer as it keeps the heat localized to the pins rather than hot air or IR which can inadvertently heat up other components on the board if you are not careful. Otherwise, you can use the hot air or IR rework station which will take far less them. Either way, make sure to use a liberal application of flux to promote reflow of solder. And more than anything, make sure the ROM chip is oriented in the exact same manner as it was on the damaged drive board.

Once you have successfully soldered the ROM chip onto the donor board, use a multimeter’s continuity testing functionality to ensure each lead is making an appropriate connection, check for solder bridges, and clean up the board to remove any potential electrical interferant. After the cleaning solution has evaporated, screw the donor board with the damaged drive’s ROM chip onto the damaged drive and plug it in. That’s all there is to it. Remember to practice this and all techniques like it on test boards prior to doing it on the real thing.

Did this process work for you? Do you have any suggestions from your experience? Please feel free to add your thoughts in the comments below.

 

Repairing Hard Drive Logic Boards

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