Posted By azog on July 28, 2011
After cleaning the keyboard on my SX-64, I figured to tackle my PET 4032 next. I spent several hours completely disassembling and cleaning the keyboard, down to the bare circuit board, cleaning the plungers and caps. I even did the rubber eraser thing on the contacts. When connected, only a few keys worked, the K M and U. Other than that, the keyboard was unresponsive.
I did disassemble the keyboard again, but I was also going to clean off the connector header pins. While doing that, the following caused a panic:
I don’t know how well that shows up but there is quite a bit of build-up on the pins of these two ICs. One is UC11, a 74LS145, and the other is UB11, a 10k bussed resistor network. Both of these are part of the keyboard driver.
Not sure what to do now. Don’t know the best way to clean it, if cleaning is even possible at this level. I’ll have to hook up my o’scope and see if the IC is scanning. I’m extremely wary of even trying to remove it, for fear of damaging traces.