PDP-12 at the RICM

J. Victor Nahigian donated some M221 and M222 boards for the processor and TC12 LINCtape controller. They are in pretty bad condition, but are repairable. Warren wrote a test program for the M222 boards, and some of the just donated boards actually work OK. It will be nice to have some spares. Dan (the donor) brought over the now lubricated top of cabinet fan. He had to make some special tools to disassembled it but was able to lubricate the dry bearings. We will reinstall it next week. He also dropped off the system logbook and more diagnostic manuals. More scanning for Bitsavers! It is really interesting to see the service history of this system since it was new. The LICM scanned some of the missing MAINDEC documentation so we were able to run: MAINDEC-12-D1AC-D Extended Memory Control (EXTMC12) MAINDEC-12-D8CC-D_KW12A_Clock_Test Fails test #11 where the AC should be 0000 and is 7777 on the CLRB instruction. MAINDEC-12-D8CA-D-(D) KW12 Real Time Clock Diagnostic (KW12TST) shows the same failure mode as D8CC. MAINDEC-12-D6BA VR12 Display Test Runs, but we have no display connected. We connected the 'scope to the outputs of the VC12 display controller when MAINDEC-12-D6BA was running. Without a way to interpret the intensify signal, and no persistence in the phosphor, the resulting image was not too good. At least we know that the display controller is responding to commands and outputs signals that look reasonable. We reran MAINDEC-12-D3AD-D-D Tape Control Test Part 1 of 2. It still fails at 3400 with the error message "LGP GP=GPC PRESET" printed. We reran MAINDEC-12-D3GA-D-D Tape Control Test part 2 of 2. That runs fine. I bought the matching terminator for my current probe and was able to give it a try today. The normal setting for PDP-12, PDP-8/I, and PDP-8/L core is 320mA. When we debugged the core we set the voltage regulator to the middle of the high and low voltage settings that caused periodic errors. The low going part is the read current and the high going is the rewrite current. The result turned out to be 316mV for the read. Not too bad! -- Michael Thompson