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Disassembly For Repair; Circuit Description - Kenwood VGS-1 Service Manual

Voice guide & storage unit
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VGS-1
Document Copyrights
Copyright 2009 by Kenwood Corporation. All rights re-
served.
No part of this manual may be reproduced, translated,
distributed, or transmitted in any form or by any means,
electronic, mechanical, photocopying, recording, or other-
wise, for any purpose without the prior written permission
of Kenwood.
How to Distinguish Between the Old and
New VGS-1
You can distinguish between the old and new VGS-1 as
described below.
■ VGS-1 (Old product)
The silk of the LF mark on the
old product is not printed
on the PC board.
Beat Shift Circuit
To prevent VGS-1 clock oscillation for the MCU (IC2)
from causing spurious reception to transceivers to which
VGS-1 is connected, the clock oscillator (11.0592MHz) has a
beat shift circuit with a transistor switch (Q1).
■ Beat Shift Circuit Off by MCU
When pin 94 of the MCU (IC2) goes Low level, Q2 turns
off and Q1 turns on because a 5V bias is applied to its base.
In this condition, C10 is shorted, so the oscillation frequency
is unchanged.
■ Beat Shift Circuit On by MCU
When pin 94 of the MCU goes High level, Q2 turns on
and Q1 turns off because its base is pulled down to GND.
In this condition, C10 is connected in series to the crystal
oscillator and the oscillation frequency increases by approx.
150ppm.
■ Beat Shift Circuit On/Off with External Device
When pin 94 of the MCU is in the Low level state, the
beat shift circuit turns on by designating pin 17 of the con-
2

DISASSEMBLY FOR REPAIR

CIRCUIT DESCRIPTION

Disclaimer
While every precaution has been taken in the preparation
of this manual, Kenwood assumes no responsibility for er-
rors or omissions. Neither is any liability assumed for dam-
ages resulting from the use of the information contained
herein. Kenwood reserves the right to make changes to any
products herein at any time for improvement purposes.
■ VGS-1 (New product)
The silk of the LF mark on the
new product is printed
on the PC board.
Precautions When Repairing the VGS-1
• When you repair VGS-1 used by Amateur transceivers,
install it in the Amateur transceiver if it is necessary to
install the VGS-1 in the transceiver.
• When you repair VGS-1 used by Land mobile transceiv-
ers, install it in the Land mobile transceiver if it is neces-
sary to install the VGS-1 in the transceiver.
nected CN1 connector of the external device as High level,
and the oscillation frequency increases by approx. 150ppm.
(Q2 becomes the OR circuit.)
XTAL
67
IC2 pin 94
D901
R17
PA1
High : Normal
Low : Shift
CN1 pin 17
D902
R901
BSFT
Fig. 1 Beat shift circuit
IC2
MCU
EXTAL
66
C10
X1
Q1
R19
5V
Q2

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