Tektronix 5110, Инструкция по эксплуатации

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Circuit Description-5110
The Geometry adjustment R285 varies the positive level
on the horizontal deflection plate shields to control the
overall geometry of the display. The TRACE ROTATION
control R291, permits adjustment of the de current
through beam-rotation coil L291 to align the display with
the horizontal graticule lines.
voltage due to ripple, change of current through the load,
etc, is immediately transmitted to the base of Q860 and
nullified by
a change in Q860 conduction, thus main­
taining a steady output. The output of the supply is set to
exactly —30 volts by adjustment of R878, —30 V Adj. This
control sets the conduction of Q870, which controls the
bias levels of Q865 and Q860. CR865 and Q865 provide
short-circuit protection by limiting the current through
Q860.
LOW-VOLTAGE POWER
SUPPLY AND CALIBRATOR
The Low-Voltage Power Supply circuit provides the
low-voltage operating power for the oscilloscope system
from three regulated supplies and three unregulated
supplies. Electronic regulation is used to provide stable,
low-ripple output voltages. The circuit also includes the
Calibrator circuit to produce an accurate-amplitude
square-wave output.
Power Input
Power is applied to the primary ot transformer T801
through fuse F201, thermal cutout S200, and Powerswitch
S201, and the line-selector block, P801. The line-selector
block allows changing the primary-winding taps of T801
to fit different line requirements.
Low-Voltage Rectifiers and Unregulated Outputs
The full-wave bridge rectifiers and associated filter
components in the secondaries of T801 provide filtered de
voltages for operation of the oscilloscope system or for
regulation by the Low-Voltage Regulators. The un­
regulated outputs are+200 volts, +38 volts, and-38 volts.
The +200-volt and +38-volt outputs to the instrument are
fuse-protected by F810 and F835 respectively.
Low-Voltage Regulators
—30-Volt Supply. The —30-Volt Supply, besides
providing power to circuitry throughout the instrument,
provides a reference-voltage source to establish operating
levels for the feedback regulators in the +30-Volt and +5-
Volt supplies. The regulator for the — 30-Volt Supply is a
feedback amplifier system which operates between
ground and the unregulated —38 volts. Current to the load
is delivered by the series-pass transistor, Q860 and the
supply voltage is established by the drop across R877,
R878, and R879. The feedback path is through R875, Q875,
and Q865 to the base of Q860. Any variation in output
+30-Volt Supply. The regulato30-VoltSupply
consists of series-pass transistor Q840 and error amplifier
Q850. This is a feedback amplifier system similar to that
just described for the -30-Volt Supply. R858, +30 V Adj,
provides an adjustment to set the output of the supply at
e30 volts. Q845 protects the supply in the event
the output is shorted by limiting the current demanded
from the series-pass transistor under excessive load.
During normal operation, Q845 is biased off.
+5-Volt Supply. The regulator for the +5-Volt Supply
consists of series-pass transistor Q815 and error amplifier
Q820. Operation of this feedback amplifier system is
similar to that described for the —30-Volt Supply. The
short-protection transistor, Q825, functions as described
for Q845 in the +30-Volt Supply.
Line Trigger
A line-frequency signal is obtained from thesecondary
of T801 and attenuated by R830, R832, and R834 to
provide a line-trigger source for the time-base plug-in
unit.
Calibrator
The Calibrator circuit composed of Q885, Q890, and
their associated passive components produces a square­
wave output with accurate amplitude and at a rate of twice
the power-line frequency. This output is available at the
probe test loop on the display unit front panel as a 4-
milliampere (peak to
peak) square-wave current, or as a
400-millivolt (ground to peak) square-wave voltage.
The resistive-capacitive network
at the base of Q885
receives a pulsating de voltage from full-wave rectifier
CR835-CR836 and produces a nearly symmetrical
switching signal forQ885 and Q890. AsQ890 is alternately
switched on and off at twice the line frequency, current
through R890 is alternately switched through the tran­
sistor or through CR890, the probe test loop, and R891,
producing the required test signal.
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