Battery tool repair advice for a battery charger

[Petekay]

I have a mapole 12/24v battery charger 2014 model approx.it will not charge it switches on and lights up the transformer is buzzing but no life at the 12/24v have cleaned all connections I removed the rectifier so how do I test it or just buy a new one thanks petekay

 

[Avo Mk8]

Buy or borrow a cheap multimeter (at least AC volts, DC volts, ohms, DC amps).
Do the fault finding things:-
Check AC volts out of transformer (is it buzzing like it always did, or has it started buzzing since the fault?)
Check resistance of rectifier diodes in each direction (low ohms one way, infinity the other)
Prod around to find volts. make sure switches are conducting when they are on!
Might need to sketch the circuit to make sense of what you find.
Etc.