BT139F triac dimmer circuit

there is the data sheet on it.. Test the Gate Voltage to low side of the load and make sure you are getting a trigger voltage. Normally, these units short and one or two things. They stay one at full output meaning both thyristors are shorted or, you'll get an effective dimming of 50% min with control up to 100%, this would indicate one of the thyristors are shorted and the other isn't. Getting nothing at all leads me to believe you may some other problem. You stated it has a torroid, I assume that maybe a pulse xformer for the Gate circuit for isolation. You need to test if a pulse on the input side( Primary) is actually there.

If the torroid isn't doing this job and then maybe it's a common mode choke which is needed to remove the noise from the line. In this case, you may have a DIAC component. This looks like a Diode but its main purpose is to clamp to a short when input phase reaches a set level, this clamping normally has a capacitor that generates a pulse for the gate. You must dig into it more to know.. Btw, this package you have is a Full Pack , fully insulated plastic.. you can replace it with just about any generic type TRIAC that meets the Amps, Voltage and Trigger current that is close to the existing component how ever, I would first dig deeper before assuming the component to be bad.

And Btw, there is a Repair group you may want to ask those questions in the future. sci.electronics.repair

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tnx for the info and other group - will followup there -

I'll dig a little more, and yeah... it's a classic choke. Just had it apart on the living room floor with my VOM, so I'll snip the wires and take it down to the bench.