(3) Triac drivers. The triac drivers are opto-isolators which generate a short
gate turn on pulse.
(a) R1 and R2 for the developer heater and dryer triacs, respectively,
limit the gate turn on current.
(b) The voltage to fire the gates is generated across the triac when it is
in its non-conducting state.
(c) When the voltage across the triac is approximately 10 volts, there is
sufficient current to fire the triac gate. Be sure not to disconnect the load from the triac
when testing. If the voltage across the triac is too great, for too long, resistor R1 and/or
R2, as well as the opto-isolator, will burn out due to a current on 1 ampere flowing
through the opto-isolator. Refer to figure 4-5 to see the normal gate trigger current as
seen with a Tektronix Model 6302 current probe.
Figure 4-5. Dryer/developer current.