PDP-12 Restoration at the RICM

We did a lot more debugging on the TC12 LINCtape controller. We saw a 500ns glitch in the LMU MOTION signal that corresponded to a short slowdown in tape speed. We will investigate this next week. We entered the LINC instruction to check a single block (0707) in the left switches and a block number (0777-0000) in the right switches. When we pressed the DO key it should go to that block on the LINCtape. With large block numbers (07xx) and with the tape positioned half way through the tape it worked OK. With lower block numbers it sometimes could not find the block and searched back-and-forth on the tape. The logic analyzer showed that the block numbers were correct in a sequence of several blocks, and then it will read a bad block number. The TC12 would tell the TU55 to turn around, it would read a good block number, realize that it was going the wrong direction, and turn the tape around. It would then read a good block number, and then a bad block number, and turn around.