Hi everyone,

I have an external HDD Toshiba 4TB MQ04UBB400 that recently stopped showing up entirely on the computer. I've gone through some troubleshooting with the hard drive, but with my limited knowledge, I've not been able to solve the issue.

Condition of the HDD:
Once plugged in, the disk spins without any issue. The LED light does not show any activity and never turns on. The PCB has been fully inspected under magnification, and there are no obvious signs of damage, burns, or problems with the soldering. The ribbon cable connecting the heads to the PCB is in good condition. The platter and heads show no issues.

Here's a list of things I've done:
1. Checked Disk Management and tried to clean the port and check all connections: Not showing up
2. Checked the BIOS for the hard drive being detected: Not showing up
3. Tried multiple computers and multiple cables: Not showing up
4. I've fully visually inspected the internal components of the HDD by opening it up carefully.

At this point, I figure it must have something to do with either the BIOS chip inside the HDD or the firmware being corrupted. But with my limited knowledge, I'd rather have someone with more knowledge than myself suggest anything else I can check and/or do. I'm reluctant to try to get my hands on a new PCB and solder the BIOS chip on it as I don't have the equipment to do so accurately and reliably. However, I do have the equipment to test components, in case there is an obvious voltage I can test to see if a particular component has failed.

Any help would be greatly appreciated. Thank you.

Opening was not a good idea. I will not lecture more on that but others might. If you want advice and if the data is important, then please consult a pro, best go for an independent local one (Google). The guys here can recommend one depending on where you are based in the UK.