Background
My mum is very keen on solving puzzles, crosswords in particular. For a good number of years she has used one of these electronic crossword puzzle solving aids. Unfortunately with its daily use the on/off button became very worn and it became impossible to switch the device on and once on it has an 'auto off' function which made using it quite frustrating. Other than this problem the device worked perfectly well. A replacement would cost £20-£30. There are no spare parts available so it was a case of repair or replace! A challenge not to walk away from!
I suspected that either the circuit board contacts or the reverse of the keypad were worn. I looked at getting a repair kit which can be used to pint on a new layer of conductive rubber onto the rear of the rubber keys but instead decided to try a different approach. A couple of years ago i scrapped a banking security keypad to salvage some parts, one of which was the rubber keypad. I decided to try to remove one the conductive button contacts and transplant it into the damaged keyboard.
I suspected that either the circuit board contacts or the reverse of the keypad were worn. I looked at getting a repair kit which can be used to pint on a new layer of conductive rubber onto the rear of the rubber keys but instead decided to try a different approach. A couple of years ago i scrapped a banking security keypad to salvage some parts, one of which was the rubber keypad. I decided to try to remove one the conductive button contacts and transplant it into the damaged keyboard.
The first job was to dismantle the device and get access to the keypad. This required removing about 10 external case screws and a further 10 to allow the circuit board to be removed and gaining access to the rubber keypad.
This picture shows the very low component count on the rear of the circuit board. No DIL PQFP IC's are present. The chips are directly bonded to the circuit board, wired to it and then a blob of resin is placed over the chips to hold everything in place.
The device keypad is on the left and the donor keypad from the online banking security device is on the right. Two of the conductive pads from the donor device were carefully sliced off from the donor keypad using a very sharp craft knife blade. The conductive pads were removed from the red key of the donor keypad.
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The old worn out conductive pad from the puzzle keypad was carefully sliced off. Glue was applied to the stump of the pad and the donor conductive pad was secured in place. The keypad was left for a few hours to fully dry.
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After the glue was fully set the components were put back together and the device tested. It was now possible to reliably and easily switch the device on and off.
Assuming that the glue holds well the crossword puzzle solver should give many more years service.