On May 25, 2020 at 10:39, danieljgor said...
To answer the below, if ports1,2,3 or 4 on the RFX9600 are connected to Zone 1 or Zone 2 on the ZC21 it kills the zone and all emitters light up like a Christmas tree.
Oh, then the RFX9600 has shorted to the positive rail. You can confirm this by measuring its output voltage.
You only need to insert diodes in the IR leads. Each diode will drop the drive voltage by about 0.6V
