My neighbor took his RD-600 to a shop and they found replaced a bad cap on the controller board. All is good now.
There is a plastic key that opens the box. Went through the same thing with my neighbor. If you don't have a key, use an awl or sharp screwdriver to move the plastic inside the key hole down. That will release the door.
I'm helping a neighbor with an Irritrol RD-600. The problem is that the solenoids chatter when turned on. I disconnected all zones from the RD-600 panel and connected a Solenoid directly to the panel. When that solenoid is turned on, it will make a screwdriver chatter when put close to it. I checked the input voltage and found it to be 27 VAC. on a digital meter. I checked the voltage across the solenoid I had connected to the panel and don't get a constant AC voltage. It jumps around from 5 to ...
