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THE CONVERTER DRIVER stage drives the CONVERTER transformer. The rectified +14V output-voltage is
fed back as control via the REGULATOR
In this way, the voltages on the secondary windings of the CONVERTER transformer are stabilised. After rec-
tification and smoothing, the stabilised supply voltages are fed to the various electronic circuits in the instru-
ment.
2.2.
CIRCUIT DESCRIPTION OF THE VERTICAL SECTION
As the channel A and B attenuators are almost identical, only the channel A is described.
2.2.1.
Input Signal Coupling (see Fig.
Input signals applied to input socket A (X2) can be either a.c.-coupled, d.c.-coupled or internally disconnected,
depending on the coupling mode switch position of S17 (AC-0-DC).
In the AC position (S17A points 2 and 3) a blocking capacitor C501 paralleled by series circuit R502 and C502
are inserted in the signal path which prevents the d.c. component being applied to the attenuator. In this mode,
the lower frequency limit is 2 Hz and some pulse droop may occur when low-frequency square-wave signals are
displayed.
When DC i s selected (S17A points 1 and 2 and S17B points 4 and 5) the complete input signal (a.c.
components) is fed to the attenuator input R503, R504, R506. Thus the full bandwidth of the oscilloscope is
available.
If the 0 pushbutton is depressed, the input signal is isolated from the attenuator and the attenuator input is
earthed, as a reference for calibration or trace centering, etc.
2 . 2 . 2 .
Attenuator and Impedance Converter (see Fig. 2.2. and
The attenuator consists of a triple high-impedance voltage divider, an impedance converter and a low-impedance
voltage divider.
High-impedance and lo w-impedance attenuator
The overall attenuation is determined by the combinations of the selected sections of the high- and low-impe-
dance attenuator.
The voltage dividers of the high-impedance attenuator are controlled by reed relays.
Read relay K503 and K504 are activated in the AMPL/DIV
In the 0.2 V/DIV
When positions 2 V/DIV
signal is XI
00 attenuated by voltage divider R509 and R511.
Attenuation positions
x5
x2.5
The AMPL/DIV switch S9 controls the FET switches via resistors R557, R559 and R562. These resistors have
high-ohmic values to eliminate parasitic capacitance effects on the FET gates, thus preventing any loss of band-
width. The trimmers C504 and C512 are adjustable to obtain constant input capacitance in all attenuator
settings. The high-impedance attenuator sections
ation for a.c. signals is adjusted to conform with the resistive attenuation for d.c. signals) by means of trimmers
+
PROTECTION circuit.
8 . 3 . )
...
1 V/DIV positions of
...
FET switches conductive
8.3)
positions 2 mV/DIV
reed relays K506 and K507 are activated. The input signal is
made independent of frequency (i.e. the capacitive attenu-
are
2-7
+
...
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