Table of Contents
Advertisement
17
SERVICE NOTES
Block diagram
Fig. 3 shows that each channel has independent control
for: input coupling, attenuation, shift, balance and
polarity. The output of each channel is controlled by a
multivibrator-driven electronic switch, which feeds
the common amplifier. Operation of this multivibrator
in turn is controlled by the MODE switch SKS. The
MODE switch can either hold the multivibrator in one
of three states or select one of three operating modes
for the blocking oscillator which drives the multivibra-
tor. It will also bee seen that internal trigger signals can
be derived from one of three sources: channel A,
channel B or the common amplifier output. The latter
is automatically selected via SKS and the relay, when
the added mode is used. In this way, triggering on the
desired signal is possible and triggering on the chopper
is impossible.
Display MODE switch SKS.
In position A as well as in position B, the multivibrator
is held in the stable state that allows the signal coming
from the selected channel to pass through its electronic
switch to the common amplifier.
In the ADDED position, the multivibrator is held in
such a state that both electronic switches pass their
signals to the common amplifier where they are added.
In the CHOPPED position the blocking oscillator is
free-running either at 1 MHz or at 40 kHz, depending
on the position of SKll (inside the apparatus). Pulses
from the blocking oscillator drive the multivibrator,
which supplies anti-phase square-waves at 500 kHz or
20 kHz to the electronic switches. Thus: first the signal
from one channel will pass to the common amplifier,
Advertisement
Table of Contents
