If I were you I'd run the Apple diagnostics program ( called hardware test on older systems) and see what it finds.I've found it to be very useful.
You don't say what version of OS you are running and the technique you use to find it depends on the version.
On some older systems , you have to use the installation disks (thats the full ones which will have pretty pictures on them not the grey upgrade ones). You should still be able to use a full installation disk anyway if you have one as long as you have a disk drive. I used it on a copy of Tiger when I was running High Sierra as the OS
On systems where the OS was downloaded, it's usually on the drive in a hidden partition and you have to press a key combination at start up. You will have to do a search to find which is appropriate for your system I'm afraid.
Timing is very important and you don't always get it to work first time. You might hold the key too long or not long enough.
If you get the option to run it in 'extended mode' or something similar (sorry forget the exact term but you get the idea) definitely go for that. It will take a lot longer to run but it's definitely worth it.
It checks loads of things in the hardware and will tell you if your mother board is failing, graphics card, HD etc. Once, it told me something along the lines of ' your HD has a problem and you need to back up everything and change it as it will fail soon'. It's a brilliant set of tools
It comes with every Mac and frankly, you should always run it before you have anything changed rather than someone guessing that it's this or that.
If you have a graphics card problem, or other hardware problem, it'll most likely tell you what the problem is.
Also, if you still have a system that has the chimes on start up, the chimes are also a hardware test, each note representing a test. If there's a note missing or if the sound is off somehow, then there's a hardware problem.
Good luck.
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If I were you I'd run the Apple diagnostics program ( called hardware test on older systems) and see what it finds.I've found it to be very useful.
You don't say what version of OS you are running and the technique you use to find it depends on the version.
On some older systems , you have to use the installation disks (thats the full ones which will have pretty pictures on them not the grey upgrade ones). You should still be able to use a full installation disk anyway if you have one as long as you have a disk drive. I used it on a copy of Tiger when I was running High Sierra as the OS
On systems where the OS was downloaded, it's usually on the drive in a hidden partition and you have to press a key combination at start up. You will have to do a search to find which is appropriate for your system I'm afraid.
Timing is very important and you don't always get it to work first time. You might hold the key too long or not long enough.
If you get the option to run it in 'extended mode' or something similar (sorry forget the exact term but you get the idea) definitely go for that. It will take a lot longer to run but it's definitely worth it.
It checks loads of things in the hardware and will tell you if your mother board is failing, graphics card, HD etc. Once, it told me something along the lines of ' your HD has a problem and you need to back up everything and change it as it will fail soon'. It's a brilliant set of tools
It comes with every Mac and frankly, you should always run it before you have anything changed rather than someone guessing that it's this or that.
If you have a graphics card problem, or other hardware problem, it'll most likely tell you what the problem is.
Also, if you still have a system that has the chimes on start up, the chimes are also a hardware test, each note representing a test. If there's a note missing or if the sound is off somehow, then there's a hardware problem.
Good luck.
Additionally as an afterthought. Sudden shutdown and restart is very often associated with overheating.Not sop common in Macs it's true, and as the repair guy has had the machine open, he's probably cleaned all the dust out but it could still be clogged with dust inside the and otherwise a failing power supply.
You can download a program which will load a tray icon and keep an eye on the temperatures inside for you (sorry don't remember what it's called but there will be more than one). If you are performing a high intensity task, watch the temperature and if you see it's getting really hot and then it shuts down, then that could be a clue. You can also get info about what temp your CPU etc should run at.
Your guy has changed a few things and although putting in an SSD and changing the battery hasn't solved the problem, it will still be very useful and will improve the machine when you get the problem finally fixed.
You haven't really wasted your money- as long as you get it working again.
