HP-67 bouncing keys

[teenix]

Depending on the type of coating used, total immersion in IPA may start to dissolve the PCB coating on the top part of the PCB. I doubt it would affect them, but the plastic LED displays may suffer a bit as well.

In a previous post I mentioned I used thin plastic strips cut from cheap disposable food containers and used a scriber to cut a cross hatch pattern on both sides. These were placed under the domes and used to scrub under them with IPA. Quite a bit of brown colored grime came out, but the plastic is soft enough not to cause damage.

The trouble with IPA on its own, it that there is no protection left on the circuit board contacts if the plating on the PCB has corroded or worn though. The problem may soon come back as the thin oxidization builds up again on the exposed copper traces.

cheers

Tony