Changes

The stock DIP switch config for the steady 3 min cycle timer is, from left to right (Up = ON): up, down, up, down, down, up, down, up. This sets pins 1, 3, 6 and 8 high, and 2,4,5,and 7 low (the DIP switch numbers are backwards in reference to the IC pins). This equates to a RC time constant of 165.

Pin 13 of the IC is the RC input which is fed by a 1.1MOhm resistor and a 1uF 35v tantalum capacitor. Cross referencing those values in the datasheet chart, we get a RC timebase of ~1Hz, though measuring via scope it shows the period to be 0.66Hz (1.5sec/cycle exactly). The confusing part is that with these figures, we get a cycle time of 165 ~110 seconds, not 180 as 3 minutes would work out . Still not super clear how this works. At low values it seems tobe pretty accurate (eg. I will have to try setting switches 5 sec), but with my test of "180s" (8, 6, 5 and 4 high which should equal exactly 180s) yielded approximately 3m18s (almost 200s). Timing the stock setting gets 2m57s, or 177s.

'''U1 ''' - Motorola MC14081BCP<ref>https://www.mouser.com/datasheet/2/308/1/MC14001B_D-2315187.pdf</ref> (B-Series CMOS Quad 2−Input AND Gate)

'''U2 ''' - Motorola MC14011BCP<ref>https://www.mouser.com/datasheet/2/308/1/MC14001B_D-2315187.pdf</ref> (B-Series CMOS Quad 2−Input NAND Gate)

'''U3 ''' - N/A (Populated on other boards)

'''U4 ''' - Maxim ICM7240IPE<ref>https://www.analog.com/media/jp/technical-documentation/data-sheets/1360.pdf</ref> (Programmable Timer/Counter IC)

** P1-1:Signal Out to Relay Driver** P1-2:STOP (Local control via terminal strip) I assume this pulls pin 10 of the ICM7240 to GND(?) to reset the chip cycle. COM is referenced to GND on the terminal strip.** P1-3:START (Local control via terminal strip) I assume this pulls pin 11 of the ICM7240 to GND(?) to trigger the cycle.** P1-4:Trigger Input? (Goes to STOP terminal on terminal block as well as P2-4 on decoder module B?)

** P2-2:N/C on Main Board** P2-3:Coupled to GND via C44** P2-4:N/C on Main Board** P2-5:N/C on Main Board