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Thermistor TH1 (TH2) is used to compensate for the gain
drift due
to temperature
when
the deflection
factor is
1 mV/div or 2 mV/div.
The
signal amplifier
by the second
amplifier
is further
amplified by the cascode amplifier of U2 c, d (U4 c, d), Q7
(Q28) and Q8 (029). This third amplifier has a large gain
therefore uses the cascode-connected structure in order to
suppress
the
influence
from
the
transistor's
feedback
capacity.
—
With CH2, Q27 and Q30 from the CH2 INV Circuit. Q28
and Q29 can be switched to 027 and Q30 by the switch
provided with CH2 POSITION VR.
U2e (U4e) is the regulated power supply or the third ampli-
fier provided for improving the CMRR
of the differential
amplifier.
Between the second and third amplifier, the vertical deflec-
tion factor variation circuit is formed using the VR on the
attenuator unit. VR6 (VR15) is used for the balance adjust-
ment in this operation, and can be adjusted from the out-
side.
VR25
(VR16) is used for the balance adjustment of the
third amplifier. VR25
is the CH1
POSITION
adjustment
control and VR16
is the CH2 INV balance adjustment con-
trol.
The signal amplified by the third amplifier is sent to the
fourth amplifier via the emitter-follower of Q9 (Q31) and
Q10 (Q32). D3 (D12) and D4 (D13) are used for limiting
the amplitude of the signal.
The fourth amplifier is also a cascode amplifier, composed
of Q11
(Q33), Q12 (Q34), Q16 (Q38) and Q17 (Q39).
The vertical mode is switched at this stage by switching
016 (038), Q17 (Q39), D5 (D14) and D6 (D15) using the
vertical mode switching signal from the horizontal sweep
unit. VR23
and VR24
are used to vary the differential
amplifier current respectively as CH1
POSITION and CH2
POSITION.
Q13 and Q14 pick up signal from the fourth amplifier, and
Q13 and Q46 send a current signal to the horizontal sweep
unit for use as the CH1
trigger signal. Q14 picks up the
CH1
OUT
signal, which
is supplied through the emitter-
follower
of Q18
and
output
from
the push-pull
single-
ended amplifier of Q19
and Q20.
Q15
is the regulated
power supply for Q13 and Q14, and generates the opera-
tion current for the CH1 trigger current signal. D7 is used
for the temperature compensation of the power supply.
VR7 is used to adjust the CH1 gain, and VR8 adjusts the
gain of the CH1 trigger and CH1 OUT signals. VRQ is used
to align the DC level of the CH1 trigger signal with that of
the CH2 trigger signal.
Q35 and Q36 pick up the signal from CH2 of the fourth
amplifier, Q35 and 047 sends the power supply signal to
the horizontal sweep unit for use as the CH2 trigger signal,
and Q36 sends the same signal to the same unit for use as
the X signal. Q37 is the regulated power supply for Q35
and Q36, and generates the operation current for the CH2
trigger
and
X
current
signals.
D16
is used
for the
temperature compensation of the power supply.
VR17
is used to adjust the CH2 gain, and VR18 adjusts the
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