I tried to repair the errors and none of the suggested methods worked.
So did a clean install of mint from a usb to mate 19 32 bit… then tried booting after everything in the 8ntall worked fine …
Reboot and error 3f0 hard disk faulty.
Just like
Thought been here before !
Boot this time to a new downloaded version of lmde having failed with the copy yesterday, but no reason why.
Re ran install and selected the grub to go to sda the default. Install fine no errors
Reboot and again 3f0 error.
Reran hp test of system no errors found anywhere on disk, memory, system total.
Formatted the hard disk totally wiped every partition so it was like a new disk. No errors found no faulty sectors or tracks all reports clean.
Reboot to usb, re install but this time chose sda1 for grub. Install worked fine. System up and running as it should be. User files copied back. Just waiting to reboot and run system update.
Still have no idea what went wrong with grub in first place or why the error codes but more worrying is, will this return if there is a fault on motherboard and connection to disk could that be why it failed before. User tells me all had been well till he connected a cooling fan tray below it as temperature in his apartment was going towards 35, normal here in high summer.