9449 - no power?

Hi
I have a Scantronic 9449 (with 9427 keypad), I think the alarm went off once and then the blue strobe kept flashing. At this time there was power to the control panel, the buttons beeped but would not set the alarm, no other lights (on panel) were lit.

A friend advised to replace the battery (as it was 8+ years old), I did this the other night and now there is no power to the control panel (apart from it being back-lit).

When I connect the battery, the external bell (and strobe) go off, noise is louder when I connect mains power.

The 3x fuse seem intact (plan to replace them tonight) but could it be the transformer?