HP-50G trying to fix failed keys

[HPing]

Today, we disassembled the 50G and determined why three of the keys (0 . G) do not register.

1. Main problem: There are 3 holes punched in the soft black rubber mat between the keys & dome switches. So when the key is depressed, the "key pin" just goes through the rubber mat but no pressure is put on the dome switch (picture 1).

2. Secondary issue: A broken hinge on two of the keys (0 .); note each of the keys has 2 hinges (picture 2). In the photo, the broken keys are on the bottom row, from right hand corner the second & third keys.

3. OK: The white dome switch panel looks ok, with some wear on the white cover for 2 keys (0 .). All 3 of the keys register when I use a finger to press the white dome switch panel (maybe the 0 is slightly less tactile).

Potential causes:

1. Black rubber mat wore from use. Also, the "key pins" are very small diameter. Bigger diameter might not have punched through the rubber mat.

2. Key hinges are feeble. Beefier hinges might not have failed.

Potential fixes.

1. New black rubber mat or some type of (very) thin plastic over the mat

2. New keys. I have seen some people epoxy the keys on the hinge (glue back side only to not interfere with top case)

Any recommendations?

BTW - We found an easy way to separate the 50G's top & bottom cases. Method from an obscure old video that didn't describe steps well. Will document that later. Along with the helpful links and videos that helped with the disassembly.