Written and maintained by Örjan Smith. Last updated 2008-12-04. Please report errors.
The Toshiba MK4020GLS 2.5" hard drive runs its logic board on 3.3V instead of the more common 5V. The motor runs on 5V as usual. This means that if you want to replace it with some other drive, you need to either find a 3.3V drive, which is not very easy, or make some slight modifications to a standard drive. I have gathered some resources for the latter approach here.
The drive in my Panasonic CF-T2 broke, so I replaced it with a old drive I had lying around, a Hitachi DK23DA-20F, in accordance with these instructions. It seems to be working fine so far.
Please note that the MK4020GLS will run equally well on pure 5V, albeit with a slightly higher energy consumption. You do not need to make any modifications to your MK4020GLS to use it in another computer.
As stated above a standard 2.5" hard drive runs both its logic board and its motor on 5V, and expects to be fed a 5V current. This current is available from the drive motor power pins in your Let's Note. All you need to do is modify the connector so that the drive gets fed the correct current.
Also, the drive compartment in the CF-T2 is quite snug, so make sure the drive you are installing is no thicker than 9.5 mm.
First off, I'll give you a few tips if you have never plucked pins from a connector before. Step one is making sure you are attacking the right pins. On some drives there is a small "1" printed on the logic board at one end of the connector. There might also be an equally small "44" written at the other end. The pins are numbered in order from 1 to 44 starting at the top right end and going to the bottom left. I just lied to you, the four rightmost pins (there are actually 48 pins) are the drive identifier pins, and not included in the numbering scheme, so pin number 1 is the third from the right in the top row. Pin number 2 is located below pin 1, and pin 3 to the left of pin 1 and so on.
Depending on the construction of the connector, you might be able to simply pluck the pins off with a pair of sharp-nosed pliers without damaging anything but the victim pin. Most laptop hard drives have their pins easily accesible and can be bent at the base back and forth a few times. I would recommend using this method whenever possible, to minimize damage to the connector and surrounding pins.
To install a 5V drive in your Let's Note, you will need to modify it so that it draws power for its logic board from the motor feed. As always, read this entire section before actually doing anything!
The logic power is supplied via pin 41. Since the Let's Note only supplies 3.3V here, we can't use that. Remove pin 41. Pin 42, just below pin 41, is where the motor gets its juice. This is the mother lode of 5V goodness. The MK4020GLS draws 3.7W from this pin during startup, so it is safe to assume that it can supply at least that much, probably with a bit of margin. Check the specs of your new drive to make sure its within that range (sum up the consumption for the logic and motor during startup). My "new" drive needs 4.5W during startup, which I feel is within reasonable limits.
Next, remove pin 44. This pin tells the host that the drive is a 5V drive (Notice that the MK4020GLS doesn't have one). We don't really want to tell the Let's Note about that, as it might upset it.
According to the message board posts linked below, many drives have pins 41 and 42 internally connected, if this is true for your drive (check with an ohm meter), you are all set. If not, you need to travel a minute or so back in time and NOT remove pin 41, but instead bend it down and connect it to pin 42 (See why you should read the entire section before doing anything?). If you are handy with a soldering iron, solder it, if not, just bend pin 41 to pin 42. Make sure you do not short circuit pin 41 or 42 to any other pins than each other!
My drive was internally connected, so I just plucked the pin.
Remove pin 44. If pins 41 and 42 are internally connected, remove pin 41, otherwise bend down pin 41 and connect it to pin 42.
I have triple checked all the pin numbers in the previous paragraph, if it says anything else elsewhere this is the paragraph to go by (better yet, check the specs from the drive manufacturer). Please contact me if you find any inconsistencies.
As this entire page consists of unverified info I found while googling around, you probably want to check out the sources before doing anything.