After a few water cycles the master valve closed all on its own. I attached / removed the MV wiring several times and managed to get it to stick open. I can hear a noise in the front so I or the plumber should be able to located it.
It needs to be replaced and I like your idea of just using a manual valve. When I bought the house I added an hose bib outlet in zone 1 as I didn't know the MV was stuck open. I verified it no longer works with the valve closed. I need that outlet as it drives two motion detector sprinklers to keep
feral hogsout of my front yard.
The transformer, rated at 750ma, overheats badly. Looking at the TEST-OUTPUTS I read between 400ma to 975ma on the MV. Way to high. the 5 zones show 220 +/- 10ma each which is correct. I can put a resistive load on the output for the MV to fool the SmartLine controller but will have to add a 2nd transformer, 24vac, rated at 1amp to get the valve to close.