I have found it very difficult to plug the four cable strands from Serial/TTL adaptor to the HDD. Two of the cable strands can be plugged easily, but plugging the third one has been a nightmare to me, there just is not enough space available. I tried different starnds of cable; I even tried to make the strand connectors thiner using sand-paper but all to no avail. Those cables are widely available because they work; am I missing something ? Please help.

Thanks

These are the cable strands I am talking about:

http://www.amazon.com/gp/product/B00DUW ... UTF8&psc=1
http://www.amazon.com/gp/product/B007XP ... UTF8&psc=1

Use a more professional adapter as this:
http://www.drivestar.biz/pc-usb-terminal-p-304.html

However you can connect only 2 wires (TX + RX), GND wire is not necessary if the hard drive ground is in common with the computer ground.
If you use two different power supply (one for the computer and the other for the hard drive), to do a common ground (GND) you can use a wire that goes from the hard drive power supply metal case to the computer metal case (or to the computer power supply case).

For example you can insert a end of a cable under a screw of the metal case of the hdd power supply and the other end under a screw of the computer power supply.

If you use only one power supply for everything (hdd + terminal adapter + computer), you don't even need to build any ground connection because ground is already in common for every device.

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My firmware database:
https://mega.nz/folder/O01DkBRI

Alternatively, your ttl connection will fit this:

http://www.ebay.com/itm/Seagate-Termina ... 2582d4421a

assuming you are working with seagate?

Thank you michael chiklis and hddguru.