I dont really know where the cmos battery is located to try the other solution

hello rotherman
firstly unless you are absolutly sure about fully disassembling your laptop i would entrust it to someone more qualified to get to the bios /cmos battery,
if you do feel like having a go then the service manual is here Future proof Tim’s laptop service manuals
see 3630 manual , once downloaded , look on pdf page 9 (actual page no 4) item 26 is the cmos battery ,

and you would need to follow the instructions within the manual to actually get to the battery ,

this is posted and used at your own liability, hope this is of assistance

Hi - took to the repair shop today - it turned out to be the power supply - got a new acer one for £23 - works fine now. Thanks for your help.

well thats great news rotherman , we are please your problem has now been resolved ,
please drop by to pchf anytime

marked as "resolved"
fixit