i.zbrr.l-.:.,.q
Page 297
NOTE: Heath part numbers that correspond to the circuit
component numbers will be found in the Parts List starting
on Page 63 of this Manual.
Refer to the "X-Ray View" and "Voltage Chart"
(fold-ou
from Page 296).
CIRCUIT DESCRIPTION
1
The function of these circuits
is
to process the transmitter
audio input, provide the transceiver
TIR control functions,
and regulate the 13.8 volt input voltage to
11 volts and 5
volts for use throughout the Transceiver.
IC201 is a quad-operational amplifier, (there are four op
amps in one package). One section
is
used as a microphone
preamplifier. Phone patch inputs are
alx, processed through
this stage, which is disabled in the CW and TUNE modes to
prevent microphone audio from being transmitted illegally.
The microphone preamplifier feeds two controls on the
chassis
-
the MICICW Lwel and Vox Gain controls.
The wiper of the audio section of the
MICICW Level control
is connected to the second section of
IC201, which provides
additional gain for the transmit audio. This amplifier is
disabled in the receive mode for muting purposes. Q201 is
an emitter follower which provides impedance matching to
the balanced modulator audio input (circuit board
E).
The wiper of the Vox Gain control is coriiected to the third
section of
IC201, which drives the Vox circuitry. The front
panel Vox switch enables this amplifier. The output is
I
detected by diodes D201 and D202, and the resulting DC
i
voltage drives the Vox switch, which consists of Q203,
Q204, Q205. and 0206. Q207 is a switch for driving the
chassis-mounted
T/R relay, and Q208 provides for PlT
I
operation.
The fourth section of
IC201 is a sidetone oscillator. This
I
oscillator and keying transistors 0209 and Q210 are enabled
in the CW mode. The output of the
sidetone oscillator is
connected to the
sidetone lwel control on the rear panel,
and to the Vox amplifier, where
it
provides tonekeyed TIR
witching in the
CW
mode.
IC202
is
the 5-volt regulator, and IC203 is the ll-volt
regulator. External chassis-mounted pass transistors
(Q1 and
Q2)
are used w~th these regulators to increase the
current-handling
capacity.
1
To Next Page
Loading...
