Lewmar windlass control - problem and fix

[Ian_Edwards]

The Lewmar, hand held, wired, raise/lower controller on Eynhallow started to operate intermittently. It's about 10 years old and gets a lot of use, I prefer to anchor, rather than use marina.

I checked the switches at the plug using a multimeter, expecting to see zero resistance when the switches were pressed, but they remained open circuit, so I took the unit apart.

The micro switches looked in good condition and the circuit board clean and dry, so I checked the micro switches with the multimeter probes on the micro switch solder tabs, and they worked.

So, I figured that there were "dry joints" between the micro switch and the printed circuit board.

I re-soldered the joints with a hot soldering iron and a little flux cored solder. The unit now operated perfectly.

When I had a critical look at the design, the only thing holding the micro switches in place is the soldered joints into the PCB. These joints take the full compression load of the finger pressing the micro switch through the membrane.There no other mechanism holding the micro switches. I don't think that this a very good design, the solder tabs aren't designed to take mechanical load, they are just for electrical connection.

I just thought that other members of the forum, might be interested, since a new one is £100.

 

[RichardS]

What you've found is the usual mounting for surface-mount components like SMT microswitches.

Well done for solving the problem though.

Richard

 

[Ian_Edwards]

Hi Richard,

These aren't surface mounted, they are soldered into plated through holes, but they haven't been pushed through so that the base of the switch rests on the PCB. The base of the switch is a 1mm or so above the PCB. This means that all the finger pressure is transmitted into the PCB, and then the housing via three soldered joints, which is why I don't like the design.

Apologies, I should have taken a picture before I put it all back together, it would have made the explanation simpler, but it didn't cross my mind until later that it might be of interest to other members of the forum.