I had a couple of issues. A poorly seated DBB card. This was followed by trouble using the extender card that Cameron Cooper and I had made a while back.

SCELBI card extender

When the extender was added to troubleshoot the DBB card, it introduced noise on the strobe lines, which resulted in issues with my TTY interface. Removing the extender card, and properly seating the DBB card resolved all issues.

Next up: another attempt at printing the front panels and construction can start on the cassette interface cards.