Hi Everyone,
New member here with long-time interest in electronics, but not much experience. My power supply for my low voltage landscape lights stopped working (Nitelight 1200 watt multi-tap transformer about 8 yrs old). After disassembling it, I found that is contains a small printed circuit board that among other things holds the SPST relay (T9AS1D22-12) that connects the 120v AC power to the massive toroidal transformer. A portion of this relay case is burnt and partially melted where it abuts two large (2" long) white rectangular ceramic resistors that are cracked and need replacement also. These are not marked and I measure infinite resistance across them on my cheap multi-meter.
These are connected across the relay switch in parallel. I'm not sure of their purpose. Might they be there to help prevent arcing at the relay contacts? I would assume their resistance would have to be relatively high to keep any significant current from flowing in the transformer primary winding when the lights are off. I was wondering if anyone knew what these resistors are for and what value might be appropriate for a replacement.
I also found it interesting that they have an elaborate circuit to activate the relay when the power is turned on. The 120V is converted to 12V DC and also to 5V DC. The 5V powers an op-amp that in turn controls the base of a Darlington transistor. This allows the 12V to flow through the relay coil and activate the relay. Seems like overkill to me, but I'm sure there must be a purpose for it.
Thanks for any input.
Dave
New member here with long-time interest in electronics, but not much experience. My power supply for my low voltage landscape lights stopped working (Nitelight 1200 watt multi-tap transformer about 8 yrs old). After disassembling it, I found that is contains a small printed circuit board that among other things holds the SPST relay (T9AS1D22-12) that connects the 120v AC power to the massive toroidal transformer. A portion of this relay case is burnt and partially melted where it abuts two large (2" long) white rectangular ceramic resistors that are cracked and need replacement also. These are not marked and I measure infinite resistance across them on my cheap multi-meter.
These are connected across the relay switch in parallel. I'm not sure of their purpose. Might they be there to help prevent arcing at the relay contacts? I would assume their resistance would have to be relatively high to keep any significant current from flowing in the transformer primary winding when the lights are off. I was wondering if anyone knew what these resistors are for and what value might be appropriate for a replacement.
I also found it interesting that they have an elaborate circuit to activate the relay when the power is turned on. The 120V is converted to 12V DC and also to 5V DC. The 5V powers an op-amp that in turn controls the base of a Darlington transistor. This allows the 12V to flow through the relay coil and activate the relay. Seems like overkill to me, but I'm sure there must be a purpose for it.
Thanks for any input.
Dave
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