[Leighton]

Hi Ray,
I’ve measured one of the solenoids in isolation, and it reads 35 Ohms resistance. Measured from the terminal blocks they’re between 35 and 38 ohm depending on the cable run lengths. A couple of my normal zones are at about 38 Ohm and trigger reliably, but the master solenoid at 38 ohm doesn’t – presumably because another zone is already active.

After writing that, I pulled it out to have a proper look at it. I noticed the voltage across the main capacitor was just sitting at power supply voltage, which seemed wrong, also I could detect no boost voltage at all. A closer inspection of the board shows that QB2 has blown, and possibly QP2 as well. I’m also measuring dead short across across RP2, but that could be QP2 acting up. My best guess is that RP2 has failed short and blown QB2. QP2 might be ok. I can’t see anything else that’s obviously blown, so I guess I’ll grab a couple of parts and see what that does.

Edit: After desoldering some bits, QP2 and QB2 are both blown.

Cheers,
Leighton…

[Leighton]

Hi Ray,
Sorry for the delay, I’ve been busy with other projects, but the winter sprinkler ban just kicked in here so I’ll be looking at this again. I switched over to a 12vdc power supply – this results in one of the master solenoids triggering sometimes, but not reliably enough to depend on. The more distant master solenoid wouldn’t trigger at all (when under water pressure – it works when under no pressure). It’s actually not the holding current that’s the problem – it’s the initial in-rush current. If I turn on the zone, then manually turn on the solenoid (using the manual release), then back off again, the zone will stay on. At 12VDC these solenoids will often trigger even without a higher voltage triggering pulse, so I’m guessing there may be something wrong with the boost circuit – I’ve seen a higher voltage, but maybe there’s not enough stored power in the cap for some reason.

Cheers,
Leighton

[Leighton]

Hi Ray,
Thanks for the response. I’m not using pump start relays, they’re just standard 24VAC solenoids (the original was a Weathermatic 12000, and when it stopped working I replaced it with a brand new Weathermatic N100 I had spare). One master solenoid is on town water, and the other from a tank which has an automatic pump, so they’re both always pressurised (the pump switches on when it detects a pressure drop).

Cheers,
Leighton Haynes

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