Re: Push-push switch repair (need some theory of operation)


Well I did this yesterday and it was even easier than expected. Removal was just a matter of solder-sucking and wicking. Heat gun didn't work a damn. If my desoldering gun had been working it would have been even easier, but it wasn't. Insertion was just a matter of tack-soldering a pin at each end with the PCB vertical, then fllipping it horizontal and going over each hole. Plenty of solder in each hole, as some of them have connections on the top side, and the holes aren't through-plated. Did the switches one at a time so I could inspect the topside soldering of at least one of them on the inside where they meet.

I didn't bother with the green spacers as they wouldn't fit on the flat pins on the new switches. Fit to the switch shafts was perfect.

I sourced the switches for about $A6.50ea from X-On, which is the Australian version of Mouser. They used to have an MOQ of 25 on them but it dropped bo 2 between the two times I looked.

Only remaining issue with the 7CT1N is that with PNP selected the dot is at bottom right, not top right. Am I right in thinking this is controlled by S70D, which is the part nearest the latch? All connections look OK and seem functional considering things like resistance to ground that should and shouldn't occur in the two positions. It's actually not a showstopper, as I can always adjust the vertical offset myself, but it's annoying.


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