Kenwood TKR-740 Service Manual page 40

TKR-740
5.4 AF PA circuit
The AF PA circuit is an AF amplifier for driving speakers to
monitor received audio signals. This circuit consists of IC45.
The 4W audio output can be provided to an external 4 ohm
speaker by supplying pow er supply voltage through the 15-
5.5 Display circuit
The display circuit contains 7-segment LED D700, D701
(orange: see the operation manual for details of display), D703
(green: circuit pow er supply), D704 (red: transmit), D705
(green: busy), tw o-color LED D702 (green: internal; red:
external reference state), LEDs in sw itches S700 to S705,
IC700, IC701, IC702 and IC703 to display this model channels
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CIRCUIT DESCRIPTION
pin test connector " SPO, SPG" on the rear panel. The
impedance of the internal speaker is adjusted to provide an
audio output of about 0.2 W w hen the internal speaker installed
on this model front panel is used.
Fig.24 AF PA circuit
and states. IC700 to IC703 are shift registers w hich convert
serial data from the CPU to parallel data and light LEDs. Q706,
Q707, Q708, Q709, and Q710 are sw itching transistors w hich
control two-color LED D702. IC704, IC705, and IC706 are three-
pin AVR ICs w hich produce pow er used for the display circuit.
Fig.25 Display circuit