Resurrecting a PDP-12 in Duluth

Here is a list of all the replaced ICs as a result of our -30V mishap. Thanks to Warren for writing it up. The picture shows the white tags on all the cards we replaced something on. (Apologies for the weird formatting. Some lines appear to be bold when I didn't tell them to be bold. Oh well.) Cards tagged, but okay: Slot E19 M121     tests ok. Slot M216 M623     tests ok. Cards repaired:      1. Slot AB22 M222     pin BV1 bad.                                         BV1 is RTRF RWB 10 OUT H     Replaced E14 7450                                         probably not caused by -30v problem.                                         (this output not used for bit 10,11)                                         (only 0,1;4,5;7,9).      2. Slot A35 M111       pin U1 stuck low.                                         U1 is LWN MARK WORD H                                         U1 is E4-8                                   Replaced E4 7400      3. Slot A38 M212       pin

Its been a while since the last post, so theres a lot to update on. A couple weeks ago we let the magic smoke out of a couple of ICs. We found a lot of cards with bad outputs. We replaced everything we found. After we replaced all of these it started working again. I will post soon with a write up of everything we replaced... there were lots of 7474s and 7400s. On Friday 7/07/17 we decided to try to get the second 4k stack working. We started up Warrens Tune 3 program and selected data field one with a 6211 instruction. We took initial measurements with the multimeters and oscilloscope. The two voltages that we needed to keep an eye on were across pins M2-V2 and S2-R2 on slot F2. M2-V2 is the core voltage and S2-R2 is the thermistor voltage. On initial startup M2-V2 was 20.31V and S2-R2 was 563mV. The initial pulse length for field 1 was 224ns.   We adjusted the pot until we got errors in an attempt to find the center point for the pulse length. At 267ns we had 50-100 e