PDP-12 at the RICM (Michael Thompson)

Some progress on the PDP-12. We borrowed a TU56 tape head from the TU56 in the warehouse and replaced the broken right head. We reran ran MAINDEC-12-D3AE-PB PDP-12 TAPE CONTROL TEST, PART 1 OF 2. The diag runs OK, so at least the timing track in the borrowed tape head is OK. We reran MAINDEC-12-D3FB-D Tape Data Test. This diag searches for the block number, but rocks the tape back and forth after finding the block. If you put the tape a long way from the beginning of the tape the diag will move the tape in the correct direction. We connected Warren's logic analyzer to the data signals that from the tape heads and the register outputs that have the current block number. It looks like there are glitches on Data Track 1. We swapped the G882 modules in F07 and F09 for tracks D1 and D3. D1 looks much better Swaped the G882 modules back to the original slots and both D1 and D3 look OK. Maybe just a bad connection between the G882 module's gold fingers and the backplane's tin connector contacts. Now it looks like the current block number in the tape controller logic is reasonable, and it looks like it can find blocks on the tape. The Tape Data Testdiag still does not work, so next week we debug the write & read logic in the LINCtape controller. -- Michael Thompson