Mystery MMD-674U Service Manual 2
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DISASSEMBLY INSTRUCTIONS
1.Mounting Box: Slide out the mounting box in parallel.
2.Top cover: Release screw at the back of top cover, and pull
out the cover.
3.Bottom Cover: Turn over the unit to release the screws at the back
of bottom cover and one the top surface. Pull out the cover.
4.Disassemble the Panel:
Pull out the Front panel.
Release the left side and right side screws attached to with the base.
Pull the base out of the unit.
5.Disassemble the mechanism deck:
There are two screws to lock the mechanism deck at front ,Unscrew
both of them.
Remove the solder from fixed wires on the main, and remove the deck.
6.Disassemble the key board :
Release four screws .
Remove the back panel .
Then remove the key board.
7.Unscrew the left side bracket and the right side bracket. There are
two screw on each side.
8.Disassemble the main board :
9.Unscrew two screw at the leef bracket
remove the solder from the Tuner,and main board.
Uncrew two screw ar the ANT.Remove the solder from fixed wires.
Unscrew two crew at the Heatsink.
Remove the main board.
03
OPERATION CHECK
GENERAL SPECIFICATIONS OF SIGNAL
Standard frequency
AM 1000 KHz (600, 1400 KHz)
FM 98.0 MHz (90.0, 106.0 MHz)
Signal output
AM 74 dB/uV
FM 60 dB/uV
Modulation
AF output level
Power source voltage
AF load impedance
Balance
Tone
AM 1 kHz 30%
FM mono
1 KHz 22.5KHz
AM/FM
DC 14.4 V (backup voltage is the same as this )
4 ohm pure resistance
Mechanical center
Mechanical center
The signal strength read in this section is voltage on the antenna.
Note : Use an RF generator for the AM band and a sweep
generator for the FM band.
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DVD DECK
DVD DECK
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ADJUSTMENT
FM IF/RF ADJUSTMENT
Equipme nt Required
FM IF/ RF signal generator
Osc illoscope
Solid-state voltmeter (SSVM)
Frequency counter
Reg ulated DC power supply
DC digital voltmeter
Distortion meter
FM IF and RF Alignment Using FM Signal Generator
Note : Press the radio power switch to turn on the radio. Signal
generator
output must be kept as low as possible to avoid overload
and clipping.
Setup Generator
Coupling
IF FM RF
signal
generator
to ANT i/p
RF
Low
High
Signal
generator
to
antenna
receptacle
Generator
10.7 MHz
sweep
output
60 dB/uV
90MHz Int 1
KHz 22.5KHz
mod. output
30dB/uV
106MHz Int
1 KHz 22.5
KHz mod.
output 30
dB/uV
Display
Setting
98.0
Mhz
90 MHz
106 MHz
Indicator
Coupling
Connect
oscillosc
ope
to Ic1
pin 3 &
ground
SSVM
across
speaker
Adjust ment Remarks
T1
-
C3
L1
Adjust so
that
maximum
AF output
power and
minimum
distortion.
Adjust AF
output
power
for
maximum
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ADJUSTMENT
AM /RF ADJUSTME NT
Equipme nt Required
>AM/RF signal generator
>Os cilloscope
>Solid-state voltmeter (SSVM)
>Frequency counter
>Re gulated DC power supply
>DC digital voltmeter
>Di stortion meter
AM/RF and RF Alignment Using AM Signal Generator
Note : Press the radio power switch to turn on the radio. Signal generator
output must be kept as low as possible to avoid overload and clipping.
Setup
RF Signal
RF
Cont.
Generator
Coupling
generator
to antenna
receptacle
Signal
generator
to
antenna
receptacle
Generator
600 KHz
Int 1 KHz
30% mod.
Output
74 dB/uV
1400 KHz
Int 1 KHz
30% mod.
74 dB/uV
Display
Setting
600
Khz
1400
Mhz
Indicator
Coupling
SSVM
across
speaker
SSVM
across
speaker
Adjust ment Rem arks
C1
L3
Adjust
AF output
power for
maximum
Adjust AF
output
power
maximum
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TROUBLE SHOOTING
Before going through the check list, check wiring connection.
If any of the problems persist after checklist has been made,
consult your nearest service dealer
Symptom
No Power
CD Cannot Be
Loaded or Ejec te d
No Sound
Causes
The car igniti on k ey n ot
been switche d on
The fuse is blow n
A CD is alread y in si de t he
player slot
Inserting th e CD i n re ve rs e
direction
The CD is extrem el y di rt y or
defected
Temperature in si de t he c ar i s
too high
Condensati on
Volume is at mini mu m
Solution
If the power sup pl y is p ro pe rl y
connected to t he c ar a cc es so ry
terminal, sw it ch t he i gn it ion
key to ACC
Replace a new fu se
Remove the CD fr om t he p la ye r
and insert the n ew o ne
Insert the CD wi th t he l ab el
facing up
Clean the CD or tr y to p la y
a new one
Cool off until the ambient
temperatur e re tu rn t o no rm al
Leave the play er o ff for an
hour or so and try a ga in
Adjust volum e to d es ir ed l ev el
Sound Skippi ng
The Operatio n Ke ys
Do Not Work
The Radio or
Automatic Se le ct io n
Does Not Work
Wiring is not pr op er ly
connected
The installa ti on a ng le i s mo re
than 30
CD is extremel y di rt y or
Defected
The built-in microcomputer is
not operatin g pr op er ly d ue t o
Interferen ce
The antenna ca bl e is n ot
connected co rr ec tl y
The signals ar e to o we ak
o
Check wiring c on ne ct io n
Adjust the ins ta ll at io n an gle to
less than 30
Clean the CD or tr y to p la y
a new one
Press the RESE T button or
reinstall th e fr on t pa ne l
properly
Connect the an te nn a ca bl e
correctly
Select the sta ti on m an ua ll y
o
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