Refurbishing Rheostats
Posted: 18 May 2017, 15:18
We needed a prac that involved 12 Rheostats . As usual I was alerted to the fact that the last time anyone used them they were really touchy and could I check them out . Indeed they were . Connecting a light bulb in series with them and a power pack , the light would flicker and/or die as the slider was moved up and down the resistor .
I looked at the cost of new ones and realized I was looking at over $1000 to replace them with a similar quality unit .
So I fixed them .
These are the type ,they were very common in schools and although they are over 40 years old , they ended up as good as new .
Start by undoing the screw at the end of the slide bar and the nut at one end of the rod that goes through the Resistor. (They are Nylock nuts so they will be tight until almost completely undone .)
Disassemble the bits .The important thing to watch are the two little springs in the slider don't go ping .
Start by scrubbing the top of the Resistor with a scouring pad .It should quickly go from dull and grimmy to shiny .
Also give the slide bar a gentle wipe after cleaning with metho . The Slide bar is Chrome plated so you don't want to be too aggressive and damage the plating .
In all of mine , the Carbon Brush had worn a groove in it . .......see those little springs ......don't loose them .
I held the slider assembly parallel and run it up and down a coarse file a few times and it easily removed the worn groove .
I looked at the cost of new ones and realized I was looking at over $1000 to replace them with a similar quality unit .
So I fixed them .
These are the type ,they were very common in schools and although they are over 40 years old , they ended up as good as new .
Start by undoing the screw at the end of the slide bar and the nut at one end of the rod that goes through the Resistor. (They are Nylock nuts so they will be tight until almost completely undone .)
Disassemble the bits .The important thing to watch are the two little springs in the slider don't go ping .
Start by scrubbing the top of the Resistor with a scouring pad .It should quickly go from dull and grimmy to shiny .
Also give the slide bar a gentle wipe after cleaning with metho . The Slide bar is Chrome plated so you don't want to be too aggressive and damage the plating .
In all of mine , the Carbon Brush had worn a groove in it . .......see those little springs ......don't loose them .
I held the slider assembly parallel and run it up and down a coarse file a few times and it easily removed the worn groove .