ILS Strobe Lighting Systems
DOC-3400-MNL Rev23.doc
(9/22/2021)
Copyright 2007-2021 ITL, LLC Page 66
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Day Circuit
The Day capacitors C2A-C2E get charged through the high voltage rectifier board PCB2
500VD to 1000VDC. The positive side of the capacitors (red wire) connects to
TB1-1 through the flash choke L1 and day/night relay K3 terminal 7. In Day mode relay
K3 is de-energized.
Night Circuit
The Night capacitor C3 gets charged through the high voltage rectifier board PCB2 output
+500VN, the night resistors R1A and R1B), and the night choke L1 to 1000VDC. The
positive side of the night capacitor (red/black wire) connects to TB1-1 through the
day/night relay K3 terminal 5. In Night mode relay K3 is energized.
Discharge Circuit
The discharge circuit is used to remove high voltage from the system by automatically
discharging the day and night capacitors when power is removed from the strobe light or
one or more flash head interlock switches are opened. The coil of the discharge relay K1
is powered by the secondary 120VAC from the power transformer T1 terminal 8. When
power is applied to the strobe light and the interlock switches are engaged the discharge
relay energizes enabling the capacitors to charge through the high voltage rectifier board.
Discharge resistor R2 is wired to the cathode side of the capacitors. The other terminal of
R2 goes through the normally-closed terminals on the discharge relay K1 to high voltage
rectifier board PCB2 terminal HVDIS. The HVDIS circuit on the high voltage rectifier
board is connected together with the day bank capacitors through diodes insuring that all
capacitors discharge. Under normal conditions R2 will discharge the capacitors in less
than 20 seconds. Once all capacitors have been discharge correctly both neon lights on
the high voltage are off.
The system also has a secondary or backup bleeder resistor R3. Due to the size of R3 it
will take several minutes to discharge the system with this resistor.
Trigger Circuit
The trigger circuit begins on power transformer T1 terminals 14 and 15. This is a
120VAC output winding dedicated for the trigger. This 120VAC connects to the trigger
board PCB1 on connector J4 pins 7 and 8.
On the timing and trigger board this voltage is full-wave rectified and used to charge a
3.3uF trigger capacitor. For the purpose of triggering a SCR is used to quickly discharge
