FCFC part 2

Fake chips from China (FCFC): faulty 8279 chips

The 8279 Programmable Keyboard/Display Interface from Intel is a device from 1976 that controls a keyboard and a 16-digit display. I use the 8279 in my PIONEER project.

Front and back side of a 8279 chip

An oscilloscope capture of a "good" 8279 chip looks like this:

It's selecting diplay digits 0 to 15 again and again.
A dead chip does nothing at all:

Expected interrupt signal after a key press:

Actually dead (no response on key press):

The front side after using nail polish remover, too easy to remove the markings:

IMO it's very hard to get fully functioning original chips almost 50 years later.
Some of my chips have a working diplay but fail to recognize key presses, others are completely dead.
For the next release of my PIONEER project I'll work on an 8279 replacement.