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switch , the transformer and rectifiers provide
the resistance. Since the rectifiers are non
linear, this resistance varies from more than
30 ohms at low current to less than 200 ohms
at maximum current.
Capa citive Current Balance
The Current-B alance Cathode Follower com
pensates for capacitive current to ground in the
S E RIES LOAD switch and associated wiring.
The plate sweep waveform is applied to the
grid of the cathode follower by divider R 3 1 6
a n d R 3 1 7 . Current is then added t o t h e negative
return lead by C310 and C 3 1 1 which is opposite in
phase to that drawn by the stray capacitance.
C 3 1 1 can be adjusted so no capacitive current
flows in the current measuring resistors.
Meter Circuit
The Meter Circuit consists of a 200 IL a meter
from serial number 1 0 1 to 5 1 20 and a I rna
meter from serial number 5 1 2 1 and up. The
Meter Circuit also has associated multiplying
resistors along with the meter. The INDICA
TION switch selects either the + D C ,
-DC
or
HEA TER supplies for application to the meter.
The heater voltage is taken from fixed taps
on the heater transformer and rectified in 0350
and 0351. The meter indicates heater voltage
as a percentage of the voltage selected by the
HEA TER switch.
" M A I N " POWER SUPPLY D I AGRAM
Transformer
The " mainll power transform e r ,
T40 1 ,
supplies plate and heater power to all cir
c uitry in the instrument except the floating
s upply tubes and circuitry. The two primary
w i ndings can be connected in series for 234-
volt operation or in parallel
for 1 17 -volt
operation.
One primary winding is tapped
to supply the voltage required by the plate
sweep transformer.
Negative Supplies
Terminals 7 and 9 connect to V 405 in a full
w ave circuit to supply voltage to the negative
1 50 volt supply.
A gas-diode Voltage - Ref
e rence TUQe , V 407 , establishes the reference
voltage for the - 1 50 volt supply. This reference
voltage is applied to the cathode of a Comparator
Tube, V4 1 0 , and is compared with the voltage
on a divider connected between the - I SO-volt
bus and ground.
R41 3 , labeled - 1 50 ADJ,
determines the
percentage of voltage that
appears at the grid of V 410 and thereby de
termines the total voltage across the divider.
Any variation from the normal grid to cathode
voltage on V 4 1 0 appears as an amplified error
s ignal at the plate.
This error signal is
applied to the grid of the Series Regulator
Tube . V4 1 2 .
This dc- coupled error signal
controls the plate resistance of the series
regulator tub e , changing it in the proper direct
ion to compensate for any change in output
voltage.
C 4 1 2 increases the ac gain of the
feedback loop to reduce the ripple.
V 403 is connected in a full wave circuit with
its output added to the - I SO-volt supply to
provide a -300-volt unregulated supply. This
s upply is used to supply other circuits which
are insensitive to voltage variation s .
Positive Supplies
V483 and V484 supply
+
400 volts , unregulated ,
to the positive-voltage supplies
and other
c i rcuits which are insensitive to voltage varia
tions.
The - 1 50 volt supply is used as the reference
voltage for the positive voltage supplies. In
the
+
300 volt supply, the voltage at the junction
of R492 and R493, which is located between
+ 300 volts and - 150 volts , is compared with
ground potential in the Comparator Tube , V489.
The amplified error signal is applied to the
S eries Regulator Tub e , V495. R496 reduces
the current through the series tube.
C492
i ncreases the ac gain of the feedback loop.
The + 100 volt supply is similar to the
+
300
volt supply with V470B as the Comparator
Tube and V 470A as the Series Regulator.
flOATING POWER S U P PLY DIAGRAM
Transformer
Transformer T501 supplies plate and heater
voltage for the Floating Power Supply. Shields
are used around the windings to minimize the
effects of capacitive currents.
AA
Circuit Description -Type 570
3 - 5
Summary of Contents for 570
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