COMPONENT MAINTENANCE MANUAL
IN 1502H RADAR INDICATOR
TM109102
1-35
May/01
When Q5005 switches on, it grounds terminal 1 of T5001 and terminal 3 of T5002.
The centertaps of each transformer r12 volts via Q5008 when the LVPS is on.
Thus, when Q5005 conducts, a positive voltage is induced at the base of Q5001 and
also on the base of Q5004. The collector of Q5001 is connected to +28 volts and the
emitter of Q5004 is connected to ground. When these two transistors switch on, the
path for current flow is through the proportional drive winding (terminals 6 and 7) of
T5001, the primary of transformer T5003, capacitor C5001, the primary of output
power transformer T5004, proportional drive winding of T5002 and finally to ground
through Q5004.
When Q5006 conducts, it switches the ground to the opposite ends of the primaries of
T5001 and T5002, causing Q5002 and Q5003 to conduct.
The proportional drive winding of each transformer (T5001 and T5002) has a 1:15
turns ratio with the secondary windings connected across the base and emitter of
each power transistor. Thus, when one of these transistors conducts, the current
through the proportional drive winding induces a corresponding current gain of 15 in
the operating transistor. The output of the circuit, across the primary of T5004, is a
sinusoidal current that swings positive (terminal 2) when Q5001 and Q5004 are
conducting and negative when Q5002 and Q5003 are conducting.
The current waveform produced is always the same shape and is determined by the
resonant frequency of the LC circuit. The output frequency of the VCO determines
how often the transistor pairs are switched on, but has no effect on the current
waveform shape. Refer to Figure 1-7 for examples of the current waveform at different
operating frequencies.
Frequency is maximum at full load and with the line voltage slightly above the point at
which the undervoltage shutdown circuit turns off the LVPS.
The document reference is online, please check the correspondence between the online documentation and the printed version.
