Goldstar OS-7020 Service Manual page 21

Trigger
Preamp
The Trigger Preamp circuit amplifies the internal trigger signal
to the level necessary to drive the Trigger Generator circuit.
Input signal for the Trigger Preamp circuit is obtained by samp-
ling the signal applied to channel 1 or the composite vertical
signal from _the Vertical Switching circuit.
This circuit also -provides a signal to the Horizontal Amplifier
for X-~ operation.
Trigger Generator
I
The Trigger · G enerator circuit produces trigger pulses to start
the Sweep Generator circuit. These trigger pulses are derived
either from the internal trigger signal from the ve r
t i
ca L defle-
ction system, an external signal connected tq the external TRIG
Input connector or a sample of the line voltage applied to the
instrument.
Controls are provided in this circuit to select trigger level,
slope and source. The trigger MODE switch determines the oper-
ating mode for the trigger circuit. In the NORM position, a
sweep is produced only when a trigger pulse is received from the
Trigger Generator circuit. Operation in the AUTO position is the
same mode as NORM position, except that a free-running trace is
displayed when a trigger pulse is not present or when the ampli-
tude of the trigger signal is not adequate.
Sweep Generator
I
The Sweep Generator circuit produces a sawtooth voltage which is
amplified by the Horizontal Amplifier circuit to provide horizon-
tal deflection on the CRT. This sawtooth voltage is generated
on command(trigger pulse) from the Trigger Generator circuit.
The Sweep Generator circuit also produces an unblanking gate to
unblank the CRT during sweep time.
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