help with old fruit machine

Hi , I recently purchased an old fruit machine ( fun nudgin criminals ) it works but on startup the screen displays AB50 no other info then runs , however it very often displays ( no win available ) is this a fault or just some dip switch setting ? the machine is red machines / barcrest with mpu 5 2006 , i have no manual , anyone know what the various dip switch settings are ? I t rarely pays out , so I would like to increase the chances of winning , it’s just for home use , any help would be much appreciated thsnks