Open the case and remove the printed circuit board. Be careful not to touch the solder joints or the bare metal leads as the capacitors will hold a charge and zap you with a nasty shock.
OK with the battery connectors towards you look to the left hand side of the circuit board and you will see a big 150uF 400v capacitor, its an aluminium can about 20mm high 10mm dia with a black plastic sleeve and 150uF 400v on it. to the right see a component with coloured rings which are BROWN GREY YELLOW Its a 1/2 watt resistor. Its purpose is to be a pseudo load and discharge for the 150uF capacitor.
It blows/burns out without any visible sign of damage. replace it with a 180K Ohm 2 WATT resistor you can buy from ebay or if you are an electrician or electronics engineer Maplin sell 2 watt resistors you can cobble in series to make 180Kohm.
BINGO ! I think you will find it works.
If it doesn't then check the soldered in 2.5 amp fuse. Now the entire board and components are coated in varnish so you need to really scratch the varnish off to get a good connection for the meter leads.
If it still doesnt work ( though its unlikely ) replace the electrolytic capacitors ( the components that stand vertical with a plastic sleeve with something like 47uF 30v on them there are two.
I hope this helps.
Jet provost pilot