Battery Charger Parts

[CamaroCracka]

I have an old Craftsman charger/booster I fear the digital panel is going out on. I was thinking the other day how a lot of modern improvements are nice, but digital button panels seem to just ensure you will end up throwing away a perfectly good appliance because they don't make the part anymore. Plus, they tend to cost about 10 times what the old analog switches and rheostats they replace cost.

Low and behold the wife ran across the beauties below at a garage sale an picked them up dirt cheap. The big one seems to work except for the 2A setting and the smaller one only works on boost, which leads me to believe the amperage control is the first thing to go out on these things. As they sit, they were worth the $20, but I'm thinking with my electromagical background, I might be able to restore them to their former glory, at least functionally.

This brings me to the question I am posing, particularly to the older timers older than me. Are these just rheostats that control the voltage/amperage sent to the battery? Does anyone still sell parts for these old Shumacher chargers. I remember my automotive mentors having these chargers when I was young and they seemed indestructible. Would really be nice to have one in prime working condition without and digital readout or button panel.