Tektronix 184, Instruction Manual

Page: 11 / 95

attached to the output connector and preserves the rise
and fall time of the time-marker pulses.
Power Supply
The power supply for the Type 1 84 consists of th ree reg­
ulated dc voltages. Circuit details for the suppl ies are shown
on the Power Supply schematic.
Power for the dc regul ator circuits is suppl ied from th ree
ful l-wave bridge rectifier power suppl ies connected to sec­
ondary taps of a single transformer T501 . These regulators
will maintain a constant regulated output with ac input
fluctuations of 94.5 or 1 37.5 or 1 89 to 275 volts. The primary
of T501 consists of equal windings which may be connected
in parallel by SW501 for 1 1 5 volt input or in series for
230 volt ac input power. A crystal oven is wired inde­
pendently to the ON-OFF switch SW400 so power is ap­
pl ied to the heater of the 750 C oven as long as the in­
strument is connected to a power sou rce. The circuit for the
OVEN indicating neon is complete with the thermal switch
closed. This neon is therefore an ind icating device of
proper operation of the crystal oven thermostat. The volt­
age regul ators are mounted on the second countdown
board with the exception of the power transistors 0527,
0547 and 0587, which are mounted on the main frame
heat sink.
-30 Volt Supply
The -30 volts is the prime supply and the reference volt­
age for the other dc regulated supplies. The circuit con­
sists of 0583 connected as an emitter fol lower to drive a
series current regulator transistor 0587.
Error sensing is accompl ished by the comparator ampli­
fier 0566 and 0576. Reference voltage for the -30 volt
supply is established by Zener diode 0560 at approximately
9.1 volts at the base of transistor 0566. The bias on the
other half of the comparator 0576 is obtained from a volt­
age divider consisting of R574, R570 and potentiometer
R572 (the -30 volt Adjust control). When R572 is properly
adjusted the output voltage is exactly -30 volts.
®I
Circuit Description-Type 1 84
+
1 2 Volt Supply
The -30 volt supply is the reference voltage for the
comparator amplifier 0536 and 0546. The output of the
comparator amplifier is appl ied to the base of emitter-fol­
lower 0543 wh ich controls the current through the series
current regulator transistor 0547.
+
1 25 Volt Supply
The
+
1 25 volt regulated supply is similar to the + 1 2
volt regulator except for the differential comparator. Volt­
age error signals are ampl ified and applied to the emitter­
follower 0523 which controls the current through the series
regulator transistor 0527.
Marker and Trigger Selection Switches
Ti ming freq uencies and timing markers are applied through
the MARKER SELECTOR switch to the MARKER OUTPUT
connector. Trigger signals connect through the TRIGGER
SELECTOR switch to the TRIGGER OUTPUT connector. The
circuit arrangement is shown in the Marker and Trigger
Selector switch schematic in the Diagrams section.
Markers from .1
fLS
to 5 s, connect through the push­
button switch to the base of emitter-follower transistor
0403. The output of this emitter follower at the MARKER
OUTPUT connector J405 is greater than 1 volt into 50
Q.
1 0 ns to 50 ns sine wave frequencies are connected
through the MARKER SELECTOR switch, directly to the
MARKER OUTPUT connector. 1
fLS
to 5 s markers connect
through a polarity switch to the marker amplifier, which
provides a time-marker signal of either (+) or (-) polarity
and greater than 25 volts in amplitude to the OUTPUT
connector.
The TRIGGER SELECTOR switch (SW425) center contacts
connect to the output of decade time markers from 1 fLs
to 1 s. Contact is made through pushbutton contacts and
applied to emitter-follower transistor 0423. The output is
a minimum trigger pulse of 0.4 V into 50
Q
termination at
the TRIGGER OUTPUT connector J425.
3-3