If your Seagate hard drive was bought at retail, then you are lucky. Seagate will fix your drive for free! See this Seagate Forum Post for more information about how to contact Seagate Tech Support to have them fix the issue for you.
If your drive is an OEM drive, then you're probably out of luck. My drive came with a Dell computer. It was under warranty, so Dell sent me a replacement hard drive, but they wouldn't do anything to help with data recovery. I was stuck with either paying someone to have it done, or doing it myself. I'm a pretty frugal guy, and the DIY method didn't sound too intimidating, so I gave it a try and was successful in un-bricking my drive.
These instructions are meant to be fairly comprehensive, with lots of pictures. After reading through them once, you'll probably want to refer to the Short & Simple Instructions for fixing your own drive.
I've read through a few other web pages to gather this information. The main one was this MSFN thread. You need to read through that entire thread to get good information though - the OP has a few things wrong and is corrected by another poster in later posts.
NOTE: I am not an expert. I've gathered these instructions from other places and successfully followed them to repair my own drive. I do not guarantee that they will work for you. Proceed at your own risk.
You will also need a Torx T6 screwdriver for removing the hard drive's PCB.
Finally, you'll need various wires and connecters for putting everything together. I simply made do with what I had lying around, and if you're the type of DIYer who's actually considering this project, you'll probably be able to do the same.
The most important part, and the one you are least likely to already possess, is a serial-line TTL adapter. This is a device that will allow you to connect a computer to the serial line of the hard drive, allowing you to send it commands and receive replies (the hard drive is really a little computer itself). A direct serial-line connection won't work, because the RS-232 spec uses 12v, while the hard drive prefers about 3-5v. So you'll need some sort of adapter.
I picked this RS232-to-TTL Adapter from alldav.com. It connects to a computer's serial port, and it only costs $4, including shipping:
(click to enlarge)
Of course, this will only work if you own a computer with a serial port. Many modern computers do not have serial ports. If you don't have one, you could try this USB to UART adapter instead. It's $6 shipped. The good news is that less soldering should be necessary, since it is powered from the computer's USB port. I haven't tried using one of them, so I can't guarantee that it will work. Other people have had luck with random cell phone USB adapters that happened to contain the right type of electronics. The MSFN thread referenced above contains more information.
SATA power connector in order to connect the 3.3V line to the RS232-to-TTL adapter. Click on the pictures to enlarge. Here's a connector:
Here is the RS232-to-TTL adapter with the power supply wires connected, as well as a couple of short wires soldered to the RX & TX contacts to act as a poor-man's "header".
I didn't have a connector that would plug into the outlet on the hard drive. I did have one from an old PC that was just a bit too large - I think it was an internal connector for the lights, or maybe the PC speaker. This picture shows one of the ends of my cable. Click on the image to enlarge:
(click to enlarge)Finally, I wrapped the contacts in electrical tape to make sure they don't touch each other or anything else. These connect to the RX & TX pins on the hard drive. But don't connect them just yet - we're going to test the adapter first.
There are small tabs on the black plastic connector. If you lift up on these, you can pull out the contacts. These contacts are the right size for connecting to the hard drive's RX and TX pins:
putty, but any terminal program will do.
Configure your terminal program to use the serial port with the following settings:
Next, create a loopback connection on the adapter. All you need to do is connect the RX & TX pins of the adapter together. These pictures show a loopback being created by connecting a wire between the contacts that will eventually connect to the hard drive:
NOTE: Commands for you to type are in red boldface. Pay attention to upper & lower case - it is important.
After a few seconds, Press CTRL+z. You should then see a prompt like this:
If not, you may have the TX & RX wires swapped. Switch them and try again.
Access Level 2 (type /2):
F3 T>/2 (enter)
Wait about 20 seconds, then spin down the motor:
F3 2>Z (enter)
Spin Down Complete
Elapsed Time 0.147 msecs
If you instead see a message similar to this:
LED: 000000CE FAddr: 00280D4D
Then you entered the commands too quickly after supplying power to the drive. Cycle power, wait 20 seconds, then begin again.
Very carefully, remove the cardstock that you placed between the PCB and the drive head contacts. Carefully replace and tighten the 3 loose screws. If you removed the screws, I suggest using a small piece of masking tape to help you hold the screws while you put them back in place.
Then start the motor:
F3 2>U (enter)
Spin Up Complete
Elapsed Time 7.093 secs
Next go to Level 1 (type /1):
F3 2>/1 (enter)
And do a S.M.A.R.T. erase (create S.M.A.R.T. sector):
F3 1>N1 (enter)
When the prompt comes back up, turn off power to the hard drive, wait a few seconds, then turn it back on. Wait about 20 seconds, then finally do partition regeneration:
F3 T>m0,2,2,0,0,0,0,22 (enter)
After 15-30 seconds, you should see something like:
Max Wr Retries = 00, Max Rd Retries = 00, Max ECC T-Level = 14, Max Certify Rewrite Retries = 00C8
User Partition Format 10% complete, Zone 00, Pass 00, LBA 00004339, ErrCode 00000080, Elapsed Time 0 mins 05 secs
User Partition Format Successful - Elapsed Time 0 mins 05 secs
Do not turn off drive until you see this message.
Once seen, drive can be turned off.
Power down everything, place drive back into your computer, and confirm that it's working.