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2-10
Amplifier
2.2.3.
The channel A trigger signals for both time-bases are picked-off from pins 14 and 15 of integrated circuit D504
The circuit of D504 (known as a Cherry-stage) converts the voltage input signal into a current output signal
(pins 12 and 13). Transistor V509 serves as a current source for D504.
In the three most sensitive AMPL/DIV positions (2,5, 10 mV/DIV) the amplifier has a gain of ten, controlled
via D504, pin 2, from the AMPL/DIV switch.
Potentiometer R571 controls the current source circuit to give adjustment of the x l / x l O gain balance.
The x10 gain of the amplifier in the AMPL/DIV positions 2,5, 10 mV/DIV can be adjusted by potentiometer
The supply voltage
of
In this way the temperature drift in the x10 gain mode is compensated to prevent bandwidth loss.
The gain XI of channel B can be adjusted by potentiometer R779 to equalise the XI gain of both vertical
channels.
From the amplifier D504 (pins 12 and 13) the output current signal i s routed to the vertical channel switch via
transistors V516 and V517. These transistors function as a current mirror and also compensate for trace shift
when t h e signal is inverted (POSITION control pulled). Potentiometer R604 (NORMAL/INVERT BAL)
provides the shift compensation.
2.2.4.
Vertical channel selection logic
DISPLAY
*
4
0
B
0
CHOP
0
4 LT
0
ADD
+
CHOP
TRIG VIEW
+
ALT
TRIG VIEW
Fig. 2.4. Vertical channel selection logic
D504 is applied to pin 9 via transistor V513.
X501
A3
A4
B2
0
0
1
0
1
0
0
1
1
1
1
1
1
0
0
1
1
1
1
1
1
1
don't care
=
vertical channel i s selected
=
D634
A2
P5
P6
P7
0
1
0
1
1
1
1
o-tl
1
1
1
1
1
0
0
1
0
1
1
0
0
1
0
1
A
B
TRIG
D632
VIEW
P8
0
0
0
0
1+1
0
0
0
0
0
0
0
0
0
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