Polar 76em Trouble with keypad not functioning, only some of the keys

Suddenly today the keys in the yellow outlined area in the picture below stopped functioning. Any ideas? Other keys seem to function fine.

 

Hi,
It's seems, most probably the problem will be in the ribbon cable connecting the cards back panel (CU) and the keyboard. if this happens suddenly, there might be some rats around your print shop. Check the cable first. If not, let's go further step by step.

 

Thanks for your response. The ribbon cable is intact and plugged in properly on both ends. We don't have rodent issue in out plant.

 

Hi,
Then most probably the problem will be with the keyboard itself or with the KDI card. This can extend from a simple PCB trace disconnection to burnt IC. Since your display and other keys are working, the voltages should be OK. (But better you can check the voltages). Do you have a way to check the KDI card? The best way is to move the KDI card to another similar machine. Then we can make sure it's working or not. If the card is good then we'll move into the keyboard.

 

Today I checked the ribbon cable connections and the condition of the ribbon cables going from the main display down to the controller boards at the bottom of the machine. Everything seems fine. I also unplugged and visually inspected the KDI board. The limit of my IC troubleshooting is checking the pathways on the PC board for continuity and I did check a few of those that also seemed fine. I did check the 2 voltage taps on the Keyboard and one of the voltages was low, (The 9V tap was reading 8.8 or something like that) The 5V tap was fine.
I "think" the issue is with the keyboard PC board and I am working with a local contractor on my parts options with replacing this.
I don't have a similar cutter here to interchange parts to.

 

Check the keyboard pathways too before you go for a new keyboard