As you may know, first step of diagnostics on Seagate drives is to check terminal output after power on and check is drive able to read system files.
But there a lot of firmware errors when you can’t access terminal – got T> string after pressing Ctrl Z. In terminal log you have last message something like:
但也有不少错误的固件，在希捷硬盘数据恢复时当您无法访问终端 – 按Ctrl Z后能够得到T>字符串信息。但是在最后终端的日志消息类似：
At this situation you should try to short read channels.
Where to short?
You need to search for differential pairs – two pair PCB traces that are going between main chip and headstack contacts. Like this:
If there is a resistor inserted between the lines – it’s definetely read channel.
At some drives there is no resistor on both lines – so only one way to find read channel is to check both differential pair:
Since the PCB on the drive is fixed to HDA, you should short-cicuit transitional openings on the external side of board.
How to short?
You should to use tool with as low resistance as possible. We recommend to use pincers with holding a paperclip.
There is two shorting techniques, depends on does the drive has diskware or no.
First one (for drives without diskware) is short before power on, and after power on trying to reach terminal by Ctrl Z
Second one (for drives with diskware) is short after power on and second “SpinUp” message in terminal, and keep shorting until “NO HOST FIS” message appeared after power on trying to reach terminal by Ctrl Z
How to check is there diskware or no? Simply. If drive hasn’t diskware – with isolated heads it will give a terminal access and print output of Ctrl L command without any LED error.
The sign of right shorting is motor stop, going to readiness state is not obligatory (in fact, after shorting only Moose family drives are going to ready state). If drive doesn’t stop the motor – it has hardware malfunction or you shorted no correct way.
After that you must be able to reach T> string after pressing Ctrl Z, spin up the drive by T>/2U command and then have access to all terminal commands (like /7X, V1, V40 etc.).
Summary. Why my shorting doesn’t work?
Possible reasons of non-working shorting may be:
1) wrong points 短路位置错误
2) wrong moment for shorting or duration 短路时刻错误的或持续时间
3) wrong instrument 不正常的工具
UPD. If you have a latest 6.1.x version you can patch the ROM and after that you will easily catch right moment for shorting – you need just make a shorting before utility handshaking invitation. As alternative you can short the spindle motor.
However this hack has a limitation: it wouldn’t work at Pharaon, Moose, Wyatt and Crocket-like drives. In this case you will see an error “Code segment not found” in utility log.