27-12-2017, 04:40 PM
I would question the connections on the SCR.
When the zena conducts and triggers the SCR it should shunt the zena and resistor so that nothing flows in the zena/resistor.
It should never blow the zena.
Test the SCR on an analogue meter such as an AVO on low ohms.
It should trigger when it is the right way round if the gate is touched on the right probe and reset when the probes are touched together.
You can also test it with a battery or bench power supply and a bulb.
When the zena conducts and triggers the SCR it should shunt the zena and resistor so that nothing flows in the zena/resistor.
It should never blow the zena.
Test the SCR on an analogue meter such as an AVO on low ohms.
It should trigger when it is the right way round if the gate is touched on the right probe and reset when the probes are touched together.
You can also test it with a battery or bench power supply and a bulb.
