2012 Macbook Pro Unibody

Definitely agree with @leroydouglas as the hard drive SATA Cable is most likely bad. The hard drive SATA Cable on the 13" non-Retina MBPro has an extremely high rate of failure especially when used with an SSD. You can test this theory by removing the SSD and booting the SSD externally using a USB to SATA Adapter, drive dock, or enclosure (assuming that the fault did not damage the file system or OS).

If you are not getting a startup chime, backlight on the display, or sleep/power LED, then you have some sort of hardware issue. The most common reason for a Mac laptop not to power on is due to a bad or completely discharged battery. Disconnect the battery and try powering on the laptop again. Also try an SMC Reset while the battery is still disconnected and try powering on again. Observe the fan to see if it spins up at all. If the laptop still won't power on, then disconnect the hard drive SATA Cable from the Logic Board and try powering on the laptop again. Is the Magsafe LED lit?

zanderstruwig wrote:

Hi all

I replaced my HDD in my mid 2012 MBP with a Crucial MX500 SSD and it worked well for a few months and then one day while I was using the laptop it froze up and I switched it off and when it came back on the folder with the question mark reappeared. I tried to reinstall MacOS but the laptop doesn't seem to detect the SSD anymore.

I am thinking of buying a different brand SSD but not sure if this would fix the problem.

My other suspicion is that it may be the Harddrive cable and thinking of replacing the cable before buying a new SSD.

Any advice on which of these two options would be best will be appreciated.

Replace the SATA cable especially when upgrading from HD to SSD it is a known weak point.

SATA replacement 15" MBP mid-2012

https://eshop.macsales.com/item/Apple/9230084#15_inch

SATA replacement 13"MBP mid 2012

https://eshop.macsales.com/item/Apple/8211480/%20%2013%22%20MacBook%20Pro%20SATA

Sounds silly, and assuming you have not ... try unattach and reattach the HD cable a couple of times. The reason old cables fail with new drives is that the old drive cable was shaken too much by spinny drives and contacts in the cable wear down and those contact points are key.

Since you did not mention an external enclosure ... part of a backup strategy is an external enclosure for a drive. I have a clone (CarbonCopyCloner, bombich.com) and an enclosure to swap drives. The clone can boot (use the "option" key) if the internal fails or can "clone back to internal" for faster drive replacement.

OWC sells good enclosures (BestBuy has a few, a MicroCenter also if one of the 20 or so stores are close to your house) and can help verify if the internal parts are broken or the drive is broken. If only the internal parts are bad the system will boot with the "option" key, or if the drive is bad the external enclosure will also fail to respond. Either way, you will have an enclosure for future use ... new systems have soldered-on SSDs and service replacement units do not include recovering your old drive. Eventually you will have one of these new units and "clone back" is the easiest way to rebuild after a unit is swapped due to damage.