There are two small glass tube fuses in the top left hand quadrant of the circuit board, labelled F1 and F2.
F1 is 1A quick blow, F2 is 250 mA quick blow. Sizes are 20mm long and 5mm diameter. Prise out of spring holder and check with eye or preferably with meter. In my case F1 was blown and gave the !!!!Check!!!! Low batt indication.
The in-line Fuse in the positive battery lead can be unscrewed for visual check/meter check.
if you need to change the battery, can be sourced from