Repairing a vintage Switchcraft switch
Posted: Thu Feb 05, 2009 6:23 am
The SPDT-off switch in my '57 U1 has been broken for sometime. I replaced it with a cheap Carling from the Shack, but could never find a modern reissue of the og Switchcraft, which was bought in bulk from a bankrupt oven maker. Fixing it turned out to be simpler then I thought.
Here's a look inside:
Four tabs on the edge hold the fiber base on. There are 6 tabs towards the center that hold the contacts in place - DON'T REMOVE THOSE! Gently bend the four tabs back just far enough to slide the base out - they are VERY fragile.
Inside the workings are simple. The handle is connected to a stiff rubber (possibly Delrin) piece. This slides against a greased rocker with contacts in the middle and at either end. Indentations lock the rubber in place. The rocker is copper, and you can see the green corrosion which has built up over the last 51+ years. One side of the switch was dead; the other made contact but with 1k ohms resistance.
Using a bit of emery cloth, I gently cleaned off the corrosion and excess grease. I was careful not to sand any thickness off the metal. You can see how shiny the right side of the rocker is compared to the uncleaned left side.
After all the contacts were clean I gently pushed the whole assy back together and bent the tabs forward. Checking with a meter, both sides of the switch now work and read <1ohm resistance. SUCCESS!!!
Here's a look inside:
Four tabs on the edge hold the fiber base on. There are 6 tabs towards the center that hold the contacts in place - DON'T REMOVE THOSE! Gently bend the four tabs back just far enough to slide the base out - they are VERY fragile.
Inside the workings are simple. The handle is connected to a stiff rubber (possibly Delrin) piece. This slides against a greased rocker with contacts in the middle and at either end. Indentations lock the rubber in place. The rocker is copper, and you can see the green corrosion which has built up over the last 51+ years. One side of the switch was dead; the other made contact but with 1k ohms resistance.
Using a bit of emery cloth, I gently cleaned off the corrosion and excess grease. I was careful not to sand any thickness off the metal. You can see how shiny the right side of the rocker is compared to the uncleaned left side.
After all the contacts were clean I gently pushed the whole assy back together and bent the tabs forward. Checking with a meter, both sides of the switch now work and read <1ohm resistance. SUCCESS!!!