HP 67 programming?

[DaveBr]

I have a HP-67 and when I first got it, it had several keys in the bottom row that varied from”mushy” to requiring seemingly way too much force to register the input.
After careful disassembly, I sprayed the key board with DeOxit contact cleaner and then passed a strip of printer paper between the metal springs and key contacts.
After reassembly, the keys feel consistent and register perfectly. I’m amazed at the quality of materials, design and assembly of HP’s early calculators and I agree, the red LEDs are Wonderful.
Dave