https://youtu.be/5hHaXGQY06M 04:27 ssh'd into the raspberry PI that connects to the paddles run from pdp8v/driver directory: ./autoboardtest -verbose -page seq 05:25 to get the serial numbers of the paddles, run: sudo ./iowlist.armv7l then put them in the iowsns.si shell script export iowsn_a=00000242 export iowsn_b=00000326 export iowsn_c=00000324 export iowsn_d=00000323 and run the autoboard test program again; ./autoboardtest -verbose -page seq 07:50 when it stopped with an error, it had IR = 1 1 1 (top 3 bits of opcode) MA = 1 1 1 0 1 1 0 0 0 0 0 0 (whole opcode for 'operate' instructions) and the error messsage said: PIN C23 (_ac_aluq) is HIGH should be LOW https://www.outerworldapps.com/pdp8v/seq_yt_err1.png 09:00 pin 1 of every paddle is ground 09:30 signal _ac_aluq says to load the accumulator with the output of the ALU at the end of this cycle 10:52 read +3.4V on pin C23 so it matches what the paddle says 12:12 report file seq.rep https://www.outerworldapps.com/pdp8v/seq.rep.txt search for where signal '_ac_aluq' is generated: 0._ac_aluq/seqcirc[0:0]3 out: J94 15.9, 2.6 1L-U5B => Q.0._ac_aluq/seqcirc[0:0]3 => J87 11.8, 0.2 Conn/ccon<23> in: D253 15.1, 2.1 <= Q.0.and2q/seqcirc[0:0]2 or D255 15.1, 2.5 <= Q.0.tad3q/seqcirc[0:0]2 or D257 15.1, 2.9 <= Q.0.dca2q/seqcirc[0:0]2 or D259 15.1, 3.3 <= Q.0.grpa1q/seqcirc[0:0]1 or D261 15.1, 3.7 <= Q.0.iot2q/seqcirc[0:0]2 or D263 15.1, 4.1 <= Q.0.grpb1q/seqcirc[0:0]1 and D264 15.1, 4.3 <= I2/bcon maq[7:7] 14:43 J94 (top pin) shows +3.4V so we got the right gate that drives pin C23 15:28 source file seq.mod https://github.com/mrieker/pdp8v/blob/github/modules/seq.mod _ac_aluq = ~ (and2q | tad3q | dca2q | grpa1q | grpb1q & maq[7] | iot2q); ...shows the and-or-invert gate that generates the _ac_aluq signal 17:00 -3.0 ---- D253 ------------- -0.6 ---- D255 ------------- -2.6 ---- D257 ------------- big NOR -> J94 -> _ac_aluq -2.0 ---- D259 ------------- -0.6 ---- D261 ------------- +0.4 ---- D263 ---\ AND ----- +5.2 ---- D264 ---/ +3.6 ---- doesn't have anything to do with this gate ! 22:50 look back in report file at that same spot to see what signal each of those diodes is connected to 0._ac_aluq/seqcirc[0:0]3 out: J94 15.9, 2.6 1L-U5B => Q.0._ac_aluq/seqcirc[0:0]3 => J87 11.8, 0.2 Conn/ccon<23> in: D253 15.1, 2.1 <= Q.0.and2q/seqcirc[0:0]2 or D255 15.1, 2.5 <= Q.0.tad3q/seqcirc[0:0]2 or D257 15.1, 2.9 <= Q.0.dca2q/seqcirc[0:0]2 or D259 15.1, 3.3 <= Q.0.grpa1q/seqcirc[0:0]1 or D261 15.1, 3.7 <= Q.0.iot2q/seqcirc[0:0]2 or D263 15.1, 4.1 <= Q.0.grpb1q/seqcirc[0:0]1 and D264 15.1, 4.3 <= I2/bcon maq[7:7] it shows D253 is signal 'and2q' D255 is signal 'tad3q' D257 is signal 'dca2q' etc so we have: and2q = -3.0V tad3q = -0.6V dca2q = -2.6V grpa1q = -2.0V iot2q = -0.6V grpb1q = +0.4V MA[07] = +5.2V 24:27 from the autoboardtest output, it shows MA = 1 1 1 0 1 1 0 0 0 0 0 0 = 7300 = CLA CLL 1110 9 8 7 6 5 4 3 2 1 0 25:20 opcode 7300 is a group 1 instruction (CLA CLL), so we should have grpa1q something like +3.0V or greater but it is -2.0V so is incorrect 25:50 look for grpa1q signal in seq.rep file to see where it is located: 0._grpa1q/seqcirc[0:0]2 out: J104 14.9, 1.1 1L-U2A => Q.0._grpa1q/seqcirc[0:0]2 => J21 14.3, 0.2 Conn/dcon<6> => D479 15.1, 1.1 D1_1.0.inc_axb/seqcirc[0:0]2<1> => D251 13.1, 1.1 D_1.0.grpa1q/seqcirc[0:0]1<1> => D273 16.1, 4.3 D_2.0._alu_and/seqcirc[0:0]2<1> in: D248 14.1, 1.1 <= Q.0.opr1q/seqcirc[0:0]2 and D249 14.1, 1.3 <= I25/acon _maq[8:8] and it shows +4.0V coming out J104 for signal grpa1q but the grpa1q signal going into D259 is -1.9V ...so something is wrong! So I look up the Sequencer PCB in KiCad to see where the trace goes.