k,
On the surface what you say does not make sense... If you have voltage coming out of the main board, then the actuators have to have voltage as each actuator has its own wiring and I find it hard to believe that a number of wires have all failed at the same time.. So, let's try this...
Each actuator has a little toggle switch with three positions.. on1, off, on2.. Move the switch on one of the actuators from one side to the other.. so if the switch is set to "on1" then set it to "on2".. The actuator should rotate (usually 180 degrees).. if it does, set the switch back to its original position and the actuator should rotate 180 degrees back to its original position.
Do the same thing on all actuators.
If none of them move that means there is no voltage coming from your Main Circuit card.. The voltage is 24 VAC....
If a valve moves one way but not the other it is generally a bad actuator micro-switch.
Please let us know the results of your test and what you are using to measure the voltage..
Thanks,
Jim R.