Trio CS-2100A, Instruction Manual, Page: 34 / 42

CIRCUIT DESCRIPTION
The o u t p u t of IC6 is used t o drive a n LED a n d as a c o n t r o l
signal for blanking a n d s w e e p s w i t c h i n g . The operation of
the trigger m o d e s w i t c h input is t h e same as for t h e horizon-
tal display s w i t c h group. Diodes D 1 3 - D 1 6 and IC1a a n d
IC1b are used t o encode 2 bits of s w i t c h status information
for this s w i t c h g r o u p after pulse shaping is done. D1 7, D 1 8
IC2a, IC2b, IC2f a n d IC3a d e t e r m i n e w h e t h e r an input is
present, w r i t i n g into t h e register IC7a and IC7b t h e a p -
propriate status i n f o r m a t i o n .
This register holds t h e s w i t c h status e n c o d e d i n f o r m a t i o n
until IC8 is used t o cancel, or return t h e status i n f o r m a t i o n
based on alternate operation of t h e switches. Similar t o t h e
horizontal display s w i t c h g r o u p , once depressed a s w i t c h
m o d e is m a i n t a i n e d until t h e s w i t c h is depressed once
more. IC5a, IC5b, and IC5c are tri-state buffers. IC9a,
IC9b, a n d IC9d — I C 9 f along w i t h Q 1 - Q 3 f o r m buffers for
the s w i t c h LED's a n d s w e e p circuit. T h e o u t p u t f r o m the
trigger m o d e reset s w i t c h is pulse shaped and sent t o t h e
trigger s w e e p circuit.
This circuit holds data even w h e n t h e instrument's p o w e r
supply s w i t c h is t u r n e d OFF. That control is p e r f o r m e d b y
Q 4 , D 1 9 , D 2 0 , IC3 and IC8a.
D 1 9 and D 2 0 f o r m a p o w e r supply based o n t h e internal
lithium battery for m e m o r y backup. I C 3 b a n d IC3c d e t e c t
t h e p o w e r OFF c o n d i t i o n and generate a m e m o r y save
signal. The o u t p u t of the above circuit f o r m s t h e set of c o n -
trol signals used t o control t h e vertical m o d e logic circuitry.
CALIBRATING VOLTAGE CIRCUIT
Q 1 1 a n d Q 1 2 f o r m a multivibrator circuit w h i c h generates a
signal w h i c h is subsequently c o n v e r t e d t o a l o w impedance
by m e a n s of Q 1 0 for o u t p u t as t h e calibration signal. It is
also used for creation of a current calibration signal by
m e a n s of R 7 0 a n d R 7 1 . The current calibration signal is
o u t p u t via a rear panel t e r m i n a l . I C 1 7 is used t o regulate the
voltage generated by this calibration circuit.
CH3 and CH4 INPUT CIRCUITS
These circuits consist of an attenuator and buffer amplifier.
Q 1 6 drives a relay t o s w i t c h t h e a t t e n u a t i o n b e t w e e n 1/1
and 1 / 1 0 . The signal f r o m t h e attenuator is impedance c o n -
verted w i t h t h e circuit f o r m e d by Q 1 3 a , Q 1 3 b , Q 1 4 and Q 1 5
and sent to the vertical pre-amplifier. The operation and
configuration of t h e C H 4 circuit is similar t o t h e C H 3 circuit.
HORIZONTAL OUTPUT AMPLIFIER
The signal f r o m t h e horizontal s w e e p circuit is amplified by
the differential amplifier f o r m e d by Q 1 a n d Q 2 . The o u t p u t
signal of this circuit is t h e n passed t o t h e e m i t t e r follower
circuit f o r m e d by Q 5 a n d Q 6 for i m p e d a n c e conversion t o
enable driving t h e circuit f o r m e d by Q 7 a n d Q 8 . Q 9 and
Q 1 0 f o r m a voltage regulation circuit w h i c h serves as the
DC load for Q 7 a n d Q 8 respectively w i t h A C peaking per-
f o r m e d by m e a n s of C 1 5 a n d C 1 6 . Q 1 1 a n d Q 1 2 f o r m an
auto-bias circuit w h i c h automatically controls t h e operating
p o i n t of t h e o u t p u t stage. It also serves as t h e b e a m finder
circuit such that w h e n the base of Q 1 3 is g r o u n d e d the
operating p o i n t of t h e o u t p u t stage is l o w e r e d , resulting in a
shrunken display.
SWITCHING POWER SUPPLY UNIT
A l t h o u g h t h e C S - 2 1 0 0 A is light and c o m p a c t and make use
of a switching regulator type p o w e r supply.
Input of either 1 0 0 V of 2 0 0 V is rectified a n d a s m o o t h i n g
capacitor is used t o generate a s m o o t h DC o u t p u t of a p -
proximately 2 0 0 V .
Next, a p o w e r transistor is used t o c o n v e r t this o u t p u t t o a n
A C voltage w h i c h is used t o drive a c o m p a c t type converter
transformer. T h e transformer used has 6 bifilar w i n d i n g s
w h i c h create six separate o u t p u t s w h i c h are then rectified
and s m o o t h e d t o provide t h e supply for t h e blanking unit
directly. One of t h e o u t p u t s is c o m p a r e d w i t h a reference
voltage t o f o r m an error voltage used for regulation. The
error voltage is sent t o t h e error voltage amplifier, the o u t p u t
of w h i c h is used to control t h e base of t h e p o w e r transistor.
This o u t p u t is isolated f r o m t h e primary by means of a
photocoupler.
POWER BLANKING UNIT
The five remaining o u t p u t s f r o m t h e s w i t c h i n g regulator
p o w e r supply are further regulated using a series regulation
m e t h o d . This a c c o m p l i s h e d w i t h Q 1 . Q 3 — Q 6 . IC1a, IC1b,
IC2a a n d IC2b are error voltage amplifiers. The + 2 0 V deriv-
e d by use of a resistance voltage divider. A conventional high
voltage D C - D C converter is used. Q 2 5 — Q 2 7 are error
voltage amplifiers w i t h Q 2 9 acting as a control transistor.
The C S - 2 1 0 0 A provides independent A and B s w e e p
intensity controls. This f u n c t i o n is i m p l e m e n t e d by means of
the circuit f o r m e d by Q 1 3 — Q 1 5 . Q 1 6 f o r m s t h e b e a m
finder circuit w h i c h allows t h e b e a m t o be seen even if t h e
intensity control has been inadvertently t u r n e d t o m i n i m u m .
Q 1 7 f o r m s t h e external intensity (Z-axis) m o d u l a t i o n circuit
w h i c h accepts an input and results in brighter displays for
increasing inputs.
The signals f r o m these circuits are c o m b i n e d at the base of
Q 1 8 t o drive Q 1 9 . Q 2 0 f o r m s t h e DC load for Q 1 9 w i t h
C 2 5 acting t o provide A C peaking for this circuit. Q 2 1 a n d
Q 2 2 f o r m t h e auto-focus circuit w h i c h apply a signal t o t h e
focus electrodes of a reverse phase f r o m t h e blanking signal.
Q 2 3 a n d Q 2 4 act t o restore t h e DC c o m p o n e n t of t h e blank-
ing a n d a u t o - f o c u s circuits b y using differential amplifiers for
isolation. Q 8 controls scale illumination w i t h Q 9 a n d Q 1 0
controlling t h e a d j u s t m e n t o f trace rotation. Q 1 1 a n d Q 1 2
are used t o adjust perpendicularity.
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