Hi all,
I have a switch which isn't making electrical contact. It consists of two leaf springs. Dead simple. They're springy enough to push against each other alright. And I've cleaned them with ethanol (didn't work) isopropyl alcohol (didn't work) and Servisol switch cleaning lubricant (didn't work either). I am at a complete loss here. Has anyone come across something like this? I can confidently say I never have!
Suggest you look for bad contact in nearby detail.
RL
You mean there may be nothing wrong with the switch itself?
I have had this happen when Hypoy gear oil has got on the contacts, but as other have said, the fault may be elsewhere. Were you making your measurements directly on the springs or on something attached to them?
A possibly short term solution is to rub very fine folded over emery paper between the contacts. It tends to destroy plated contacts but might just get the switch working.
No, I got the probes directly on the leaves themselves.
Which is what I plan to do next, in fact. I have some 3000 grit paper which should be close to perfect for this kind of thing. In fact I have a full range from 3000 right through to 40. I'm hoping it won't require anything below 1200, though!
Have you verified that the meter leads are making good electrical contact to the switch blades? Oxidation can fool any of us! Touch one probe to the switch blade, and touch the other probe further down the blade - repeat on the other side, only then check for electrical contact closure once you are certain you have good probe connections.
John :-#)#
For the future, it is best to arrange the contacts so the gap between them is vertical; that way any dirt falls out of them instead of being ground into the surface. GPO telephone exchange equipment always had the relays aligned that way.
Soak some unbleached kraft paper in alcohol or kerosene, and force between the leaves' contacting surfaces. Move vigorously in a circular patternm, then remove and retest.
Nick Hayward = Cursitor Doom ? Wouldn't have bothered, if I'd known.
RL
Acting on the advice of someone very much more experienced with this attenuator than I am, it's the case that the offending material was silicon oxide. Something to do with contact sparking and silicon grease that they used in the early versions of this device. The only remedy is fine abrasive paper. I used 1500 grit in then end; very lightly just a few strokes. it's fine again now - and before anyone says anything, there was no gold plating on these contacts to rub off!
Yeah, that's my name; don't wear it out!
That's worth remembering. I had always assumed silicone grease was fairly benign and could be used anywhere, now I know differently.
Not to criticise your decision (which I actually suggested) there are lots of other contact plating materials than gold. Some of them are thicker or softer than others. Apart from other noble metals, nickel and tin spring to mind.
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