Recondition.IT – Slide switch for crystal locked FM Radio

We have one of those three-channel crystal-locked FM Radio – commonly used for listening to the China Radio station 2CR and others.  It had been playing up at times and was unable to tune into any channel and was put aside a while ago.

It is a DP3T slide switch that is the problem.  Dual Pole 3 Position slide switch – with pin spacing at 2.5mm apart.  I was looking for alternatives and could find switches that have pins 2mm and 3mm apart, but not 2.5mm.  After some time, I was able to find a similar switch – a SK-23E01G, but would you know, I cannot find anyone who has stock of this switch.  I did find a couple of sites that do advertise this switch, but they require pre-ordering and have a minimum quantity of 1000 units – fantastic, except that I only need one piece.

My only option is to buy a new radio, or to “recondition.IT” – the switch that is.  The switch is used to select from one of three crystals that determine the frequency that the radio is tuned to.  I removed the switch from the pcb, then opened the housing.  It was immediately obvious that the switch contacts were worn and were oxidised.

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There are two movable contacts – but the fixed contacts are not allowing good contact. To fix this, I used a 240 grit emery paper, to polish up the contacts, followed by 320 grit paper.

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Now this looks better – at least the contact surfaces are shiny.  I reassembled the switch, then checked the switching resistance, and it was good.  Great, installed the switch, closed the radio, added four AA batteries, and voila – it was working.  Not bad for about 10 minutes work.

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