Restoring a Sony Ta-F7 Vfet at the moment and have come across a couple of lever switches that haven't responded to deoxit, so I have taken them apart with a view to cleaning them and regreasing them but I don't quite know how to clean them out. Is it as simple as cleaning out the old grease polishing the contacts with something like brasso then re greasing?
I would steer away from anything abrasive. Since the switch is apart anyway, you could soak the contact portion in mineral spirits, using a soft brush to clean the oxidation from the contact surface. Clean the oxidation from the pins also. Once you get the oxidation removed then give it a good cleaning up with isopropyl alcohol. Then apply a light coating of Deoxit to the contact area, and reapply some grease to the slide surface area.
Good procedure from glen65. Note that some solvents can dissolve or at least soften early moulded plastics, perhaps even the grey switch contact frame. Test them first by applying a little with a Q-tip or tissue to an outer plastic surface, rub a few times in the one spot and wait to see if the surface dulls. If it does, don't use it. I think the isopropyl alcohol will be safe for all the operations - otherwise, rubbing alcohol.
Those sliding switch assemblies usually have more wear in the moving contacts than the fixed ones we see in the pics. I assume they're inside the black mouldings? You may have to deform (bend together) those contacts to get reliable contact even after cleaning. Unfortunately, this will only be a temporary fix and once the contacts wear, you have to nurse these old switches. Replacement parts will only come from cannibalising another one that is relatively unused, since wear accelerates and if there is any significant heat generated by currents, the copper alloy spring metals will soften and lose contact pressure.
Those sliding switch assemblies usually have more wear in the moving contacts than the fixed ones we see in the pics. I assume they're inside the black mouldings? You may have to deform (bend together) those contacts to get reliable contact even after cleaning. Unfortunately, this will only be a temporary fix and once the contacts wear, you have to nurse these old switches. Replacement parts will only come from cannibalising another one that is relatively unused, since wear accelerates and if there is any significant heat generated by currents, the copper alloy spring metals will soften and lose contact pressure.
The contacts are slid over the bars then the black plastic is placed on top, moving the contacts, the switch seems to make good contact on the bench, hopefully the problem was the grease drying it out giving the switch a sludgy feel, and the fact that they have had very little use in 35 years.
Would lithium based grease be ok to use?
Would lithium based grease be ok to use?
Lithium grease is for high temperature, heavy duty bearings but it makes little electrical difference because the soap and oil which grease is composed of are an insulating mix that can only carbonise minutely at the likely switch currents. Personally, I'd use something without the soap - like petroleum jelly. (Vaseline is an everyday source)
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