Motorola Gp350 6880904z07 0 Manual

 
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6880904Z07-O August, 1996 
Intrinsically Safe Radio Information GP350 Portable Radios Service Manual
Repair of FMRC Approved Products
 
Repair
 
A repair constitutes something done internally to the unit 
that would bring it back to its original condition Approved by 
FMRC. A repair should be done in an FMRC Approved facil-
ity.
Items not considered as repairs are those in which an action 
is performed on a unit which does not require the outer cas-
ing of the unit to be opened in a manner which...

 
August, 1996 6880904Z07-O 
3-1 
Remove Battery
 
1. Locate the battery latch on the bottom of the radio.
Push the battery latch toward the front of the radio
and hold it in the open position as shown in Figure
3-1.
2. While holding the battery latch in the open posi-
tion, slide the battery down approximately 1/2 inch
and then off the radio housing as shown in Figure
3-2. 
Remove Belt Clip from Battery
 
1. Push in on tab of belt clip with small flat 
-
 
bladed
screwdriver, and at the same time slide...

 
3-2 
6880904Z07-O August, 1996 
Disassembly/ReassemblyGP350 Portable Radio Service Manual
Remove the Main Board
 
5. Pull the chassis out and away from the housing as
shown by the arrow in Figure 3-5. 
Remove the Main Board
 
1. The main board is sandwiched between the front
shield and the chassis. Four chassis clips hold the
sandwiched assembly together. Remove the chassis
gasket and place the radio shield side down on a
flat surface.
2. Using a small flat blade screwdriver, unlock the
four chassis...

August, 19966880904Z07-O4-1Section4
Theory of Operation
Overview
This section provides a detailed theory of operation for the
GP350 and its components: the microcomputer, the receiver,
the transmitter, and the frequency generation circuitry. 
Microcomputer
The GP350 VHF and UHF radios use the Motorola
68HC11A8 microcomputer, U401, which utilizes:
•7.9488 MHz clock rate
•Multiplexed 8-bit address/data lines
•16-bit addressing
•Internal watchdog circuitry
•Analog to digital conversion input ports
The...

4-26880904Z07-OAugust, 1996Theory of OperationGP350 Portable Radios Service ManualTransmitterThe insertion loss of this filter is approximately 1.9 db for
VHF and 3.5 db for UHF. The filter is designed to be termi-
nated with the amplifier output impedance on one side, and
50 ohm on the other.
The net gain from the receiver module is about (12.2 db
VHF) (10.8 db UHF) in the center of the band and about
(10.7 db VHF) (9.5 db UHF) at the band edges. The net cen-
ter of the band noise figure is approximately...

August, 1996                                  6880904Z07-O4-3GP350 Portable Radios Service ManualTheory of Operation Frequency Generation Circuitryto minimize the error produced at the emitter of Q156 result-
ing from the voltage offset at the input of U151A.
The voltage at the other input of the summing amplifier,
U151B, is supplied from two DACs contained within U152.
These DACs are controlled by the microprocessor, and pro-
vide the reference voltage for the control loop. One of the
DACs, that...

4-46880904Z07-OAugust, 1996Theory of OperationGP350 Portable Radios Service ManualFrequency Generation CircuitryWhen a “high” impedance is applied to U251 pin 5, the VCO
is operating in BATTERY SAVER mode. In this case, both
the receive and transmit oscillators as well as the receive,
transmit, and pre-scaler buffer are turned off. In the Frac-
tional-N, the battery saver mode places the   A/D and the
modulation attenuator in the off state. This mode is used to
reduce current drain on the radio.
GP350...

August, 1996                                  6880904Z07-O4-5GP350 Portable Radios Service ManualTheory of Operation Frequency Generation CircuitryLimiter (Audio Filter IC)
The audio filter IC U402 contains the limiter circuit, which
prevents over-deviation of the RF carrier by symmetrically
clipping the peaks of the modulating voltage. Audio from the
pre-emphasis amplifier circuit is coupled to the limiter. Gain
of the limiter stage is adjustable in four 3 dB steps, from -3
dB to +6 dB. Therefore, TX...

4-66880904Z07-OAugust, 1996Theory of OperationGP350 Portable Radios Service ManualFrequency Generation Circuitry15k-ohm impedance. P1-7 is always unmuted, not affected
by the receiver with squelch circuit. Option RX audio input
to the GP350 radio is available at P1-6, with a sensitivity of
100 mVrms at less than 200 ohm output impedance from
option board.
RX Audio Mute Gate 
PNP transistor Q406, the RX audio mute gate, with resistors
R458 and R459, and capacitors C432 and C433, provide
receiver audio...

August, 19966880904Z07-O 4-7INSERT PAGE SIZE AND RADIO BLOCK DIAGRAM FROM
MANUAL 6880902Z30-D, PAGE 2-7GP350 Portable Radio
Functional Block Diagram