Full Text Searchable PDF User Manual
Service Manual
GM56USB MODEM
Service Manual
Table of Contents
A. Testing Flow Chart...............................................................................................................3
B. Check U1 Pin 1 +5V ............................................................................................................4
C. Check U1 Pin 3 Data Clock .................................................................................................5
D. Check X1 Working Frequency.............................................................................................6
E. Check IC1 Pin 41 Reset Signal............................................................................................7
F. Check K4 Pin4 .....................................................................................................................8
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Service Manual
Chapter 1. Introduction
a. Hardware
PC586 above
♦
♦
♦
♦
♦
♦
♦
RJ-11 cable
USB Port
USB Cable
Speaker
b. Software
Win98 above
GM56USB Driver
c. Function Block
USB
ST7554
USB MODEM
CONTROLLER
TQFP48(7*7*1.4
MM)
STLC7550
Analog-front-end
(AFE)
TQFP48(7*7*1.4
MM)
CRYSTAL
9.216 MHZ
DAA
PC HOST
PROCESSOR
LINE
PHONE
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Service Manual
Chapter 2. Testing Procedures
A. Testing Flow Chart
Check U1
Pin 1
REPLACE U1
T
T
F
F
Check U1
Pin 3
T
Check
Working FR.
T
Check IC1
Pin41
T
F
F
F
REPLACE K4
REPLACE C5,IC1
REPLACE K1,IC2
RESOLDER R8,R9
REPLACE U1,IC2
Check K4
Pin 4
END
START
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B. Check U1 Pin 1 +5V
U1 PIN 1 +5V
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Service Manual
C. Check U1 Pin 3 Data Clock
U1 PIN 3
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Service Manual
D. Check X1 Working Frequency
C10
X1
C16
IC2
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Service Manual
E. Check IC1 Pin 41 Reset Signal
IC1
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Service Manual
F. Check K4 Pin4
K4 PIN4
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Service Manual
Chapter 3. Troubleshooting Guide
Problems Probable
Reasons
Solutions
1. Dialing
fail
1. PCB
defect
1. Replace
K4
2. Replace
IC1
3. Replace
IC2
1. Connection
fail
1. PCB
defect
1. Replace
U1
2. Replace
IC1
3. Replace
IC2
4. Replace
X1
5. Replace
C5
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Service Manual
Chapter 4. Removal and Replacement
Step Description
Picture
1. Turn
over
modem
To disassemble the modem, you
have to turn over modem.
2. Loose screws Using screwdriver to loose screw.
3. Take
apart
rear flat
After taking screw off, you can take
up the upper cover
4. Take
apart
PCB
Now, You can take apart the PCB
from the lower cover.
The PCB is the most important part
of modem.
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Service Manual
Chapter 5. Parts List
Description Part
number
Description Part
number
U1 USB6B1S08
K1309061
X1 9.216MZH K0809012
IC1 ST7550
K1309060
K4
K0917006
IC2 ST7554
K1309059
C16 27PF 0603
K1509048
C10 33PF 0603
K1509046
C5 0.1U 0603
K1509028
Chapter 6. Tools
1.Screwdriver Cross
2.Oscilloscope
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