The older chargers were pretty simple units. A large transformer to step down the AC voltage to what ever voltage was required, 2 diodes to rectify to DC output, a circuit breaker to prevent self destruction, a switch to control it, and an amp meter to register the current output. There is not much to go wrong and most parts can still be sourced for them.
The new ones have LEDs and things with a programmed life span so don't expect the modern stuff to outlast the old stuff. It just ain't going to happen.