The following procedure should be used to test the Seagate drives’ heads for HDD repair and you may need to use some professional hdd repair tools or data recovery tools.

If a drive hangs at startup, perform the first part:

*  Switch the drive to Safe Mode.
*  Load boot adaptive data and SA defects list (you can do that manually or using the following

HDD Commands
F>R1
F>R2
or with the corresponding command from the loader start dialog).

*  Load App code (the easiest way to do that is through the loader startup dialog) and start it in Safe mode
(from the loader startup dialog or using the F>j,,1 command)

*  When the drive enters the T> mode, load System Sectors (from the loader startup dialog or using the T>R command).

Note: HDD commands mentioned above are used for drives equipped with Serial Flash memory only

*  Load CERT code ad CERT tables (the easiest way to do that is through the loader startup dialog).
*  Proceed to actual testing of the firmware and drive heads.

Now you can proceed to actual testing of drive heads (the procedure from this step on can only be used when a drive
does not hang during start). To do that you either need to run test 4 or attempt to switch heads manually.

Heads switching test. To perform the test, use the ; (semicolon) terminal command to find out the number of heads in the drive (the MxHd parameter means the highest head number) and run the following series of commands:
T>/2
2>s444,0,22(The command to position over cylinder 444, head 0 is required because during drive start the variable used to store the current cylinder number in operations with the terminal can remain uninitialized; then subsequent commands will terminate with code FB, which means an invalid address. )
2>U
2>H0
2>H1

etc., where the digit after 2>H stands for the number of the head to test. If a head can “see” the surface, it will be
switched and the drive will respond with a message like:
Head …
where ellipsis will be replaced with the head number. The drive should output no other messages like $ or Head Mask
or HM. If these messages appear or the drive hangs, then the head is damaged.

Test 4. To perform the test, send the following command to the drive:
T>T4
– then it will begin sequential attempts to use allowed BIAS reading current values for all heads. The drive will output
to the terminal during the test a report similar to the following:
T>T4
Begin Test 04
ASCII logging on
LBA=1B4F93F1
ASCII logging off
ASCII logging on
Kick Off Test

Testing head 0…
DAC value = FD02
Biasing with current 0025mA
DAC value = FBEA
Biasing with current 0050mA
DAC value = FAD2
Biasing with current 0075mA
DAC value = F9BA
Biasing with current 0100mA
DAC value = F8A2
Biasing with current 0125mA

DAC value = F78A
Biasing with current 0150mA
DAC value = F672
Biasing with current 0175mA
DAC value = F55A
Biasing with current 0200mA
DAC value = FD02
Passed  Max OD Bias Current = 0200mA. Limit = 0100mA

Head Mask FFFF – Switch to full int.
Spin Ready
Testing head 1…
DAC value = FCD7

…………………………………………………………..
and so on for all heads. If during BIAS sweep the drive hangs, begins long (infinite) output of the $ or Head
Mask or HM messages, it means that the head is damaged. Here the “Head Mask FFFF – Switch to full int.“ message
in the end of the example is produced after BIAS sweep and represents a part of diagnostic messages generated during recalibration; thus it is not an error message  Moreover, if head test is failed for some BIAS, it means a damaged head.

HDD repair tools recommended: PC3k UDMA version, HD Doctor for Seagate

More HDD repair tools or data recovery tools here

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