Big cheese alarm

Hi all

My first post on here.
Bought a cheap machine off a friend at the weekend.
Barcrest Big Cheese
I know nothing about them so just after a few pointers if anyone can spare the time?

Firstly, I can't stop the voice alarm going off when I turn it on? It continuously says (loudly)
Stop over here - or something like that??
I assume it's a tilt or damage alarm?
Ive trawled the web but can't find anything conclusive?
There is a normal flat key hole that I don't have the key for that is wired up? Is this an alarm key?

Any ideas how to stop it?
The top red LED on the board is flashing red if that helps?

Also, if I can turn it off and get it working again how would I go about changing from £5 jackpot to £25?

Thanks in advance for any help

Matt