25, or 4 to 6 [Not Chicago Content]

[Geoff Quickfall]

Mel's,

If just a debouncing issue then the DEOXIT will work. This sounds a little bit more complicated.

Personally I start with the "KISS" principal or at least the medical tenant to "do no harm". I would start with the pinholes for the 4 key and the 6 key and introduce a tiny (bigger then a pinhead) drop of DEOXIT gold by placing the tiny end of the tube against the offending pinhole and squeezing, then working the button. Clean up the excess.

If this does not work I would disassemble the calc and clean all the pin contacts for the PCA and display. Reassemble and check.

Next check the PCB for corrosion and cold solder joints maybe rinsing in a white vinegar bath followed by a water rinse and thorough dry. This bath does not include the LED BLOCK. Reassemble and check.

I have actually washed the keyboard but only with water and a mild liquid dish soap solution. No nail brush but maybe a natural bristle paint brush. Do not use hot water, in some cases this may cause a bloom on the black background of the keyboard facia. This is due to the lacquer breakdown by UV light. It happens rarely and can be fixed by allowing the keyboard to dry thoroughly. If still present, some conditioners like Armoral can be applied with a Q-tip to the facia of the keyboard. Do not use alcohol or solvents as the silk screened characters will vanish.

Lastly, swear an oath to the inventor of the heat stake and then removing the caps sparingly leaving some residue for re melting. Not to be attempted by the faint of heart!

Or find a dead 25 on your favourite auction site and harvest the keyboard from it. The dead ACTS 25s are plentiful!

Cheers