Note that from the Power Input module X12 and X16 go the the water valve board #4. Since everything else comes off bd #1, that is a big clue. If you replaced all the boards, then either there is something wrong with bd #1, #2, or #3, or there is an open circuit in one of the connecting cables.
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Bd #2 is likely an AC to DC module. So, X200 & X300 will probably have DC voltages on them. X100 will have AC voltage on it. That will shut down everything except the water valve if it is bad. That would be my 1st suspect. See if you can measure any DC voltages on X301 or X201. If no, find out why, cable or bd #2. If no AC input, then bd #3.
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Bd #2 is likely an AC to DC module. So, X200 & X300 will probably have DC voltages on them. X100 will have AC voltage on it. That will shut down everything except the water valve if it is bad. That would be my 1st suspect. See if you can measure any DC voltages on X301 or X201. If no, find out why, cable or bd #2. If no AC input, then bd #3. Because of the proximity of X10 and X301, I would guess that X301 is supplying 12VDC thru X10 to bd #4. So I would concentrate on X201 voltages.
I don't think there will be a single point failure on bd #1 that will cause your symptoms.
Note that from the Power Input module X12 and X16 go the the water valve board #4. Since everything else comes off bd #1, that is a big clue. If you replaced all the boards, then either there is something wrong with bd #1, #2, or #3, or there is an open circuit in one of the connecting cables.
Bd #2 is likely an AC to DC module. So, X200 & X300 will probably have DC voltages on them. X100 will have AC voltage on it. That will shut down everything except the water valve if it is bad. That would be my 1st suspect. See if you can measure any DC voltages on X301 or X201. If no, find out why, cable or bd #2. If no AC input, then bd #3.
I don't think there will be a single point failure on bd #1 that will cause your symptoms.