On Sun, Jan 30, 2022 at 11:45:33PM -0500, Jeffrey Brace via vcf-midatlantic wrote:
Maybe others want to chime in on what they were working on.
First I tried to read the RD53 from the 11/73 discussed on the list earlier. The drive wasn't spinning up so we lifted the drive electronics board to get at the spindle motor and got it to spin. Remarkably easy to do. Two captive screws to undo one side of the board and it pivots up on some pins at the other end. The MFM reader mostly didn't see anything. One point it seemed to identify proper data for a short time. With a scope it was outputting just very narrow pulses at improper interval. We were going to try to swap the electronics board with a drive I brought but when we pulled a flex cable one of the pins stayed with the connector. Three more pins were about to break. Instead we jumpered the four lines hoping the initial broken pin was the problem. No such luck. We decided that further work was going to be time consuming. May still be possible to recover but not easy. I think he was going to try to get the tapes read and see if that goes better. I moved on to the 8/I. At end of last workshop it would single step short programs toggled in but not run at speed. Much poking and found the memory voltage was collapsing when running. Two regulator cards were bad. Swapped in a spare and one from the PDP-12 and it could run programs. Replaced bad bulbs on front panel and one bad drive transistor. Was able to load diagnostics over the serial port. Instruction test 2A passed. 2B failed with a memory location looking like it was incremented by one. The first 4k of memory passed it diagnostics. Tried to run FOCAL language. Crashed after printing CONGRATULATIONS. More for next visit. Left it with two light pattern programs that can be used to show it does something. Got to play with the front panel on the LINC for a little while. It was showing a reasonable amount of life but looks like its going to need some attention.