Panasonic SA-AK750E User manual

nAMPLIFIER SECTION
RMS output power
THD 10%, both channels driven
1 kHz
(Low channel)
110 W per channel (3 Ω)
10 kHz
(High channel)
110 W per channel (3 Ω)
60 Hz
(Subwoofer channel) 220 W per channel (6 Ω)
Total output power 660 W
nFM/AM TUNER, TERMINALS SECTION
Preset station FM 20 stations
AM 15 stations
Frequency Modulation (FM)
Frequency range 87.5 to 108.0 MHz (50 kHz steps)
Sensitivity 4.0 µV (IHF)
S/N 26 dB 2.2 µV
A
ntenna terminal(s) 75 Ω(unbalanced)
A
mplitude Modulation (AM)
Frequency range 522 to 1629 kHz (9 kHz steps)
Sensitivity
S/N 20 dB (at 999 kHz) 560 µV/m
©2007 Matsushita Electric Industrial Co. Ltd.. All
rights reserved. Unauthorized copying and
distribution is a violation of law.
SA-AK750E
SA-AK750EB
SA-AK750EG
Colour
(K)... Black Type
Music Port input jack
Terminal Stereo, 3.5 mm jack
Sensitivity 100 mV, 4.7 kΩ
Phone jack
Terminal Stereo, 3.5 mm jack
nCASSETTE DECK SECTION
Track system 4 track, 2 channel
Heads
Record/playback Solid permalloy head
Erasure Double gap ferrite head
Motor DC servo motor
Recording system AC bias 100 kHz
Erasing system AC erase 100 kHz
Tape speed 4.8 cm/s
Overall frequency response (+3, -6 dB) at DECK OUT
NORMAL 35 Hz to 14 kHz
S/N ratio 50 dB (A weighted)
Wow and flutter 0.18 % (WRMS)
Fast forward and rewind time Approx. 120 seconds with
C-60 cassette tape
nDISC SECTION
Disc played [8 cm or 12 cm]
(1) CD-Audio (CD-DA)
(2) CD-R/RW (CD-DA, MP3* formatted disc)
CD Stereo System
Notes: This model’s CD mechanism changer unit is CRS1. Please refer to the original Service Manual
(Order No. MD0509368C0) for this mechanism.
Specifications
ORDER NO. MD0703026CE

(3) MP3*
*MPEG-1 Layer 3, MPEG-2 Layer 3
Bit rate
MP3 32 kbps to 320 kbps
Sampling frequency
MP3 32 kHz, 44.1 kHz, 48 kHz
CD-DA 44.1 kHz
Decoding 16 bit linear
Digital filter 8fs
D/A converter MASH (1 bit DAC)
Pick up
Wavelength 780 nm
Beam Source Semiconductor laser
A
udio output (Disc)
Number of channels 2 (Stereo) (FL,FR)
nUSB SECTION
Playable USB Storage Media
1) HDD
2) USB MP3 Player/Digital audio player
3) USB Thumbdrives
Supported audio file format
MP3 bit rate
USB memory port
Maximum current 500 mA
Bit rate
MP3 32 kbps to 320 kbps
Sampling frequency
MP3 32 kHz, 44.1 kHz, 48 kHz
A
udio output (MP3)
Number of channels 2 channels
Frequency response (MP3) 20 Hz to 20 kHz (0+/-1.0 dB)
1 Safety Precautions 4
1.1. General Guidelines 4
1.2. Caution for AC Mains Lead 5
1.3. Before repair and adjustment 5
1.4. Protection Circuitry 6
1.5. Safety Part Information 6
2 Prevention of Electro Static Discharge (ESD) to
Electrostatically Sensitive (ES) Devices 7
3 Handling Precautions For Traverse Deck 8
4 Precaution of Laser Diode 10
5 Warning 11
5.1. Service caution based on legal restrictions 11
6 Accessories 12
S/N Ratio
USB unit out 85 dB
nGENERAL
Power supply
For E/EG only AC 230 V, 50Hz
For EB only AC 230 to 240 V, 50Hz
Power consumption 139 W
Power consumption in standby
mode
0.5 W
Dimensions (W x H x D) 250 x 330 x 323 mm
Mass 7.1 kg
Operating temperature range +5 to +35°C
Operating humidity range 5 to 90% RH (no condensation)
nSYSTEM
SC-AK750 (E) Music center: SA-AK750 (E)
Speaker: SB-AK750 (P)
Subwoofer: SB-WAK750 (P)
SC-AK750 (EB) Music center: SA-AK750 (EB)
Speaker: SB-AK750 (P)
Subwoofer: SB-WAK750 (P)
SC-AK750 (EG) Music center: SA-AK750 (EG)
Speaker: SB-AK750 (P)
Subwoofer: SB-WAK750 (P)
For information on speaker system, please refer to the original
Service Manual (Order No. MD0703011CE) for SB-AK750P/PC-K
and (Order No. MD0703012CE) for SB-WAK750P/PC-K.
Notes:
1. Specifications are subject to change without notice. Mass and
dimensions are approximate.
2. Total harmonic distortion is measured by the digital spectrum
analyzer.
7 Operating Procedures 13
7.1. Main Unit Key Buttons Operations 13
7.2. Remote Control Key Buttons Operations 13
8 New Features 15
8.1. Using the Music Port 15
8.2. Connecting and Playing a USB Mass Storage Class
Device 16
9 Self diagnosis and special mode setting 17
9.1. Service Mode Summary Table 17
9.2. Special Mode Table 1 17
9.3. Reliability Test Mode (CRS1 Mechanism) 20
9.4. Error code Table Display 21
10 Assembling and Disassembling 25
CONTENTS
Page Page
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SA-AK750E / SA-AK750EB / SA-AK750EG

10.1. Caution 25
10.2. Disassembly flow chart 26
10.3. Main Parts Location 27
10.4. Disassembly of Top Cabinet 28
10.5. Disassembly of CD Changer Unit (CRS1) 28
10.6. Disassembly of Rear Panel 29
10.7. Disassembly of Main P.C.B. 31
10.8. Disassembly of Transformer P.C.B. 31
10.9. Disassembly of Power P.C.B. 32
10.10. Disassembly of Front Panel Unit 33
10.11. Disassembly for Panel P.C.B. 34
10.12. Disassembly of Tact Switch P.C.B. 35
10.13. Disassembly of USB P.C.B. 35
10.14. Disassembly of Deck mechanism unit 36
10.15. Disassembly of Deck P.C.B. 36
10.16. Disassembly of Traverse Unit 37
10.17. Disassembly for Deck Mechanism 38
10.18. Disassembly of Deck Mechanism P.C.B. 41
10.19. Disassembly of cassette lid 42
10.20. Rectification for tape jam problem 42
11 Service Fixture and Tools 44
12 Service Positions 44
12.1. Checking and Repairing of Main P.C.B. 44
12.2. Checking and Repairing of Transformer P.C.B. 45
12.3. Checking and Repairing of Panel, Deck & Deck
Mechanism P.C.B. 45
12.4. Checking and Repairing of Power P.C.B. 46
13 Procedure for Checking Operation of Individual Parts of Deck
Mechanism Unit 47
13.1. Operation Check with Cassette Tape 47
13.2. Operation Check without Cassette Tape 47
14 Measurement And Adjustments 49
14.1. Cassette Deck Section 49
15 Voltage and Waveform Chart 51
15.1. USB P.C.B. 51
15.2. CD Servo P.C.B. 51
15.3. Power P.C.B. & Transformer P.C.B. 52
15.4. Panel P.C.B. 52
15.5. Main P.C.B. 53
15.6. Deck P.C.B. 54
15.7. Waveform Chart 54
16 Wiring Connection Diagram 55
17 Block Diagram 57
17.1. CD Servo Diagram 57
17.2. Deck/ Deck Mechanism Diagram 58
17.3. Main Diagram 59
17.4. Panel Diagram 61
17.5. Power Diagram 62
17.6. USB/ Transformer Diagram 63
18 Notes Of Schematic Diagram 65
19 Schematic Diagram 67
19.1. (A) CD Servo Circuit 67
19.2. (B) Main Circuit 68
19.3. (C) Panel Circuit 72
19.4. (D) Sub Panel Circuit & (G) Deck Mechanism Circuit 73
19.5. (E) Power Circuit 74
19.6. (F) Deck Circuit 76
19.7. (H) Transformer Circuit 77
19.8. (I) USB Circuit 78
20 Printed Circuit Board 79
20.1. (A) CD Servo P.C.B., (F) Deck P.C.B. & (G) Deck
Mechanism P.C.B. 80
20.2. (B) Main P.C.B. 81
20.3. (C) Panel P.C.B. 82
20.4. (D) Sub Panel P.C.B. & (I) USB P.C.B. (Side A & B) 83
20.5. (E) Power P.C.B. 84
20.6. (H) Transformer P.C.B. 85
21 Illustration of ICs, Transistors and Diodes 87
22 Terminal Function of IC's 88
22.1. IC7001 (MN6627954MA) Servo Processor,Digital Signal
Processor/Digital filter and D/A Converter 88
22.2. IC7002 (BA5948FPE2) IC 4CH Drive 89
22.3. IC2801 (C2CBYY000423) System Microprocessor 89
23 Exploded Views 91
23.1. Cabinet Parts Location 91
23.2. Deck Mechanism Parts Location (RAA4403-S) 93
23.3. Packaging 94
24 Replacement Parts List 95
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SA-AK750E / SA-AK750EB / SA-AK750EG

1 Safety Precautions
1.1. General Guidelines
1. When servicing, observe the original lead dress. If a short circuit is found, replace all parts which have been overheated or
damaged by the short circuit.
2. After servicing, ensure that all the protective devices such as insulation barriers and insulation papers shields are properly
installed.
3. After servicing, check for leakage current checks to prevent from being exposed to shock hazards.
1.1.1. Leakage Current Cold Check
1. Unplug the AC cord and connect a jumper between the two prongs on the plug.
2. Using an ohmmeter measure the resistance value, between the jumpered AC plug and each exposed metallic cabinet part on
the equipment such as screwheads, connectors, control shafts, etc. When the exposed metallic part has a return path to the
chassis, the reading should be between 1MΩand 5.2MΩ.
When the exposed metal does not have a return path to the chassis, the reading must be .
1.1.2. Leakage Current Hot Check (See Figure 1)
1. Plug the AC cord directly into the AC outlet. Do not use an isolation transformer for this check.
2. Connect a 1.5kΩ, 10 watts resistor, in parallel with a 0.15µF capacitor, between each exposed metallic part on the set and a
good earth ground such as a water pipe, as shown in Figure 1.
3. Use an AC voltmeter, with 1000 ohms/volt or more sensitivity, to measure the potential across the resistor.
4. Check each exposed metallic part, and measure the voltage at each point.
5. Reverse the AC plug in the AC outlet and repeat each of the above measurements.
6. The potential at any point should not exceed 0.75 volts RMS. A leakage current tester (Simpson Model 229 or equivalent) may
be used to make the hot checks, leakage current must not exceed 1/2 milliamp. Should the measurement is out of the limits
specified, there is a possibility of a shock hazard, and the equipment should be repaired and rechecked before it is returned to
the customer.
Fig. 1
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SA-AK750E / SA-AK750EB / SA-AK750EG

1.2. Caution for AC Mains Lead
1.3. Before repair and adjustment
Disconnect AC power, discharge Power Capacitors C5101, C5104, C5171, C5172, C5920, C5940 and C5950 through a 10Ω,5W
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SA-AK750E / SA-AK750EB / SA-AK750EG

resistor to ground.
DO NOT SHORT-CIRCUIT DIRECTLY (with a screwdriver blade, for instance), as this may destroy solid state devices.
After repairs are completed, restore power gradually using a variac, to avoid overcurrent.
Current consumption at AC 230 V, 50 Hz in NO SIGNAL mode (volume min at CD mode) should be ~ 350mA.
1.4. Protection Circuitry
The protection circuitry may have operated if either of the following conditions are noticed:
· No sound is heard when the power is turned on.
· Sound stops during a performance.
The function of this circuitry is to prevent circuitry damage if, for example, the positive and negative speaker connection wires are
“shorted”, or if speaker systems with an impedance less than the indicated rated impedance of the amplifier are used.
If this occurs, follow the procedure outlines below:
1. Turn off the power.
2. Determine the cause of the problem and correct it.
3. Turn on the power once again after one minute.
Note :
When the protection circuitry functions, the unit will not operate unless the power is first turned off and then on again.
1.5. Safety Part Information
Safety Parts List:
There are special components used in this equipment which are important for safety.
These parts are marked by in the Schematic Diagrams & Replacement Parts List. It is essential that these critical parts should
be replaced with manufacturer’s specified parts to prevent shock, fire or other hazards. Do not modify the original design without
permission of manufacturer.
Table 1
Reference No. Part No. Part name & Description Remarks
L5601 G0B9R5K00001 CHOKE COIL
L5602 G0B9R5K00001 CHOKE COIL
L5603 G0B9R5K00001 CHOKE COIL
L5604 G0B9R5K00001 CHOKE COIL
L5950 ELF15N035AN LINE FILTER
T5950 G4CYAYY00143 TRANSFORMER (MAIN)
T5951 G4C2AAJ00005 BACK UP TRANSFORMER
Z5950 ERZV10V511CS ZENER
RL5950 K6B1AEA00015 POWER RELAY
F1 K5D252BLA013 FUSE
FP5920 K5G103A00019 FUSE PROTECTOR
FP5940 K5G103A00019 FUSE PROTECTOR
FP5950 K5G402A00025 FUSE PROTECTOR
JK5950 K2AA2B000011 JK AC INLET
A2 K2CQ2CA00006 AC CORD EG/ E
A2 K2CT3CA00004 AC CORD EB
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SA-AK750E / SA-AK750EB / SA-AK750EG

2 Prevention of Electro Static Discharge (ESD) to
Electrostatically Sensitive (ES) Devices
Some semiconductor (solid state) devices can be damaged easily by electricity. Such components commonly are called
Electrostatically Sensitive (ES) Devices. Examples of typical ES devices are integrated circuits and some field-effect transistors and
semiconductor “chip” components. The following techniques should be used to help reduce the incidence of component damage
caused by electro static discharge (ESD).
1. Immediately before handling any semiconductor component or semiconductor-equiped assembly, drain off any ESD on your
body by touching a known earth ground. Alternatively, obtain and wear a commercially available discharging ESD wrist strap,
which should be removed for potential shock reasons prior to applying power to the unit under test.
2. After removing an electrical assembly equiped with ES devices, place the assembly on a conductive surface such as aluminium
foil, to prevent electrostatic charge build up or exposure of the assembly.
3. Use only a grounded-tip soldering iron to solder or unsolder ES devices.
4. Use only an anti-static solder remover device. Some solder removal devices not classified as “anti-static (ESD protected)” can
generate electrical charge to damage ES devices.
5. Do not use freon-propelled chemicals. These can generate electrical charges sufficient to damage ES devices.
6. Do not remove a replacement ES device from its protective package until immediately before you are ready to install it. (Most
replacement ES devices are packaged with leads electrically shorted together by conductive foam, aluminium foil or
comparable conductive material).
7. Immediately before removing the protective material from the leads of a replacement ES device, touch the protective material
to the chassis or circuit assembly into which the device will be installed.
Caution
Be sure no power is applied to the chassis or circuit, and observe all other safety precautions.
8. Minimize body motions when handling unpackaged replacement ES devices. (Otherwise harmless motion such as the brushing
together of your clothes fabric or the lifting of your foot from a carpeted floor can generate static electricity (ESD) sufficient to
damage an ES device).
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SA-AK750E / SA-AK750EB / SA-AK750EG

3 Handling Precautions For Traverse Deck
The laser diode in the traverse deck (optical pickup) may break down due to potential difference caused by the static electricity of
clothes or our human body.
So, be careful of electrostatic breakdown during repair of the traverse deck (optical pickup).
· Way of handling the traverse deck (optical pickup)
1. Do not subject the traverse deck (optical pickup) to static electricity as it is extremely sensitive to electrical shock.
2. To prevent the breakdown of the laser diode, an antistatic shorting pin is inserted into the flexible board (FFC board).
3. Do not to apply excessive stress to the flexible board (FFC board). When removing or connecting the short pin, finish the job
in as short time as possible.
4. Do not turn the variable resistor for laser power adjustment. (It is pre-adjusted during production time)
Grounding for electrostatic breakdown prevention
1. Human body grounding
Use the anti-static wrist strap to discharge the static electricity from your body.
2. Work table grounding
Put a conductive material (sheet) or steel sheet on the area where the traverse deck (optical pickup) is place, and ground the
sheet.
Caution :
The static electricity of your clothes will not be grounded through the wrist strap. So, take care not to let your clothes touch the
traverse deck (optical pickup).
Caution when replacing the Traverse Deck
The traverse deck has a short point shorted with solder to protect the laser diode against electrostatics breakdown. Be sure to
remove the solder from the short point before making connections.
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SA-AK750E / SA-AK750EB / SA-AK750EG

9
SA-AK750E / SA-AK750EB / SA-AK750EG

nUse of caution label
4 Precaution of Laser Diode
Caution :
This product utilizes a laser diode with the unit turned "ON", invisible laser radiation is emitted from the pick up lens.
Wavelength : 780 nm
Maximum output radiation power from pick up : 100 µW/VDE
Laser radiation from pick up unit is safety level, but be sure the followings:
1. Do not disassemble the optical pick up unit, since radiation from exposed laser diode is dangerous.
2. Do not adjust the variable resistor on the pick up unit. It was already adjusted.
3. Do not look at the focus lens using optical instruments.
4. Recommend not to look at pick up lens for a long time.
ACHTUNG :
Dieses Produkt enthält eine Laserdiode. Im eingeschalteten Zustand wird unsichtbare Laserstrahlung von der Lasereinheit
abgestrahlt.
Wellenlänge : 780nm
Maximale Strahlungsleistung der Lasereinheit :100 µW/VDE
Die Strahlung an der Lasereinheit ist ungefährlich, wenn folgende Punkte beachtet werden:
1. Die Lasereinheit nicht zerlegen, da die Strahlung an der freigelegten Laserdiode gefährlich ist.
2. Den werkseitig justierten Einstellregler der Lasereinhit nicht verstellen.
3. Nicht mit optischen Instrumenten in die Fokussierlinse blicken.
4. Nicht über längere Zeit in die Fokussierlinse blicken.
ADVARSEL: I dette a apparat anvendes laser.
CAUTION!
THIS PRODUCT UTILIZES A LASER.
USE OF CONTROLS OR ADJUSTMENTS OR PERFORMANCE OF PROCEDURES OTHER THAN THOSE SPECIFIED HEREIN MAY RESULT
IN HAZARDOUS RADIATION EXPOSURE.
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SA-AK750E / SA-AK750EB / SA-AK750EG

5 Warning
5.1. Service caution based on legal restrictions
5.1.1. General description about Lead Free Solder (PbF)
The lead free solder has been used in the mounting process of all electrical components on the printed circuit boards used for this
equipment in considering the globally environmental conservation.
The normal solder is the alloy of tin (Sn) and lead (Pb). On the other hand, the lead free solder is the alloy mainly consists of tin
(Sn), silver (Ag) and Copper (Cu), and the melting point of the lead free solder is higher approx.30 degrees C (86°F) more than that
of the normal solder.
Definition of PCB Lead Free Solder being used
The letter of “PbF” is printed either foil side or components side on the PCB using the lead free solder.
(See right figure)
Service caution for repair work using Lead Free Solder (PbF)
· The lead free solder has to be used when repairing the equipment for which the lead free solder is used.
(Definition: The letter of “PbF” is printed on the PCB using the lead free solder.)
· To put lead free solder, it should be well molten and mixed with the original lead free solder.
· Remove the remaining lead free solder on the PCB cleanly for soldering of the new IC.
· Since the melting point of the lead free solder is higher than that of the normal lead solder, it takes the longer time to melt
the lead free solder.
· Use the soldering iron (more than 70W) equipped with the temperature control after setting the temperature at 350±30
degrees C (662±86°F).
Recommended Lead Free Solder (Service Parts Route.)
· The following 3 types of lead free solder are available through the service parts route.
RFKZ03D01K-----------(0.3mm 100g Reel)
RFKZ06D01K-----------(0.6mm 100g Reel)
RFKZ10D01K-----------(1.0mm 100g Reel)
Note
* Ingredient: Tin (Sn), 96.5%, Silver (Ag) 3.0%, Copper (Cu) 0.5%, Cobalt (Co) / Germanium (Ge) 0.1 to 0.3%
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SA-AK750E / SA-AK750EB / SA-AK750EG

6 Accessories
Remote Control
FM Antenna Wire
AC Cord (For E/EG only)
AC Cord (For EB
only)
AM Loop Antenna
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SA-AK750E / SA-AK750EB / SA-AK750EG

7 Operating Procedures
7.1. Main Unit Key Buttons Operations
7.2. Remote Control Key Buttons Operations
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SA-AK750E / SA-AK750EB / SA-AK750EG

8 New Features
8.1. Using the Music Port
This feature enables you to enjoy music from a portable audio equipment.
With reference to page 15 of the operating instruction manual.
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SA-AK750E / SA-AK750EB / SA-AK750EG

8.2. Connecting and Playing a USB Mass Storage Class Device
With reference to page 16 of the operating instruction manual.
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SA-AK750E / SA-AK750EB / SA-AK750EG

9 Self diagnosis and special mode setting
This unit is equipped with functions for checking and inspecting namely: Self-Diagnostic and Test Mode.
9.1. Service Mode Summary Table
The service modes can be activated by pressing various button combination on the main unit and remote control unit. Below is the
summary for the various modes for checking:
Player button Remote control button unit Application Note
[ ] [4], [7] Enter Doctor Mode Refer to the section, “9.2
Special Mode Table 1 for
more information.
Mode Remote control button unit Application Note
In Doctor Mode Main unit [ ],
[4]+[7]
Display EEPROM Information Refer to the section,
“9.2.1 for more
information.
[4] Set for cold start when reset start is executed the next time Refer to the section, “9.2
for more information.
[Muting] Clock Setting Refer to the section, “9.2
for more information.
[0] Tape Eject Test Refer to the section, “9.2
for more information.
[DIMMER] All segment display for the FL Refer to the section, “9.2
for more information.
[DISC] CRS1 Inspection Refer to the section, “9.2
for more information.
[7] Volume 50 Setting check
[8] Volume 41 Setting check
[9] Volume 35 Setting check
[ ] Volume 0 Setting check
[PRESET EQ] EQ Off
[H. Bass] EQ Heavy
[PROGRAM] HIC force MUTE ON/ OFF
[5] CD To Tape recording Inspection
[6] Tape record’s playback
[SLEEP] TPS Inspection
[<] FM Tuning check
[>] Tuner STEREO/ forced MONO
[ ] FM OK/ NG (98.1 MHz)
[ ] AM OK/ NG (1000 KHz)
9.2. Special Mode Table 1
Item FL Display Key Operation
Mode Name Description Front Key
Self -Diagnostic
Mode
To enter into self
diagnostic checking for
main unit.
1. Select [
] for TAPE mode (Ensure no tape is
inserted).
2. Press and hold [ ]button for 3
seconds follow by [ ].
To exit, press button on
main unit or remote control.
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SA-AK750E / SA-AK750EB / SA-AK750EG

Item FL Display Key Operation
Mode Name Description Front Key
Doctor Mode To enter into Doctor
Mode for checking of
various items and
displaying checksum and
software version.
FL Display sequence:
Display 1 →2
(Display 1)
(Display 2)
1. All segments will light up for 1 second.
2. The Check Sum of EEPROM and firmware
version will be display.
* ROM correction
** Firmware version No:
In any mode:
1. Press [ ] button on main unit
follow by [4] and [7] on remote control.
To exit, press [ENTER] button on remote
control or button on main
unit.
CD Test Mode To enter into checking the
reliability of changer unit.
In any mode:
1. Select [ ] for CD mode.
2. Press and hold [ ] button for 3
seconds follow by [ ].
To exit, press button on
main unit or remote control.
CD Auto
Adjustment
To check the CD auto
adjustment result for
FLOCK, TLOCK and
CLVS.
FLOCK: Focus Lock
TLOCK: Traverse Lock
CLVS: Constant Linear
Velocity Speed
In CD Test Mode:
1. Press [0] button on the remote control.
To exit, press button on
main unit or remote control.
CD Changer
Reliability Test
(CRS1)
To determine the
reliability of CD Changer
Unit.
(For more information,
refer to section 9.3)
In Self-Diagnostic Mode:
1. Select [ ] for CD mode.
2. Press [ ] button.
To exit, press button on
main unit.
(The tray will return to PLAY position and then
power off)
SRVC_TRV To unlock the traverse
unit for service.
FL Display sequence:
Display 1 →2
(Display 1)
(Display 2)
In Tape mode:
1. With no cassette tape inserted,
2. Press [ ],[ ] button
on main unit.
3. Press [SINGLE CHANGE] on main unit.
To exit, press [ ] button on
main unit.
Open/ Close Test To check the function
operation of changer unit.
(For more information,
refer to 9.3)
In doctor mode:
1. Press [DISC] on remote control.
To exit, press [ENTER] button on remote
control or button on main
unit.
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SA-AK750E / SA-AK750EB / SA-AK750EG

Item FL Display Key Operation
Mode Name Description Front Key
Tape Eject Test To check on the tape
eject function (For deck
1/2)
In doctor mode:
1. Press [0] button on remote control.
FL Display Test To check the FL
segments display (All
segments will light up and
LED will blink at 0.5
second interval)
In doctor mode:
1. Press [DIMMER] button on remote control.
Cold Start To activate cold start
upon next AC power up.
In doctor mode:
1. Press [4] button on remote control.
To exit, press [ENTER] button on remote
control or button on main
unit.
Clock Setting
Check
To indicate that a clock
time was set properly
In doctor mode:
1. Press [MUTING] button on remote control.
9.2.1. EEPROM Checksum (ROM Correction)
Purpose: To check for microprocessor firmware version and EEPROM checksum (ROM correction).
Below are the procedures for this mode.
Step 1: Enter into Doctor mode (for more information, refer to section 9.2 on the key operation to enter into this mode.
Step 2: (By pressing STOP button on main unit followed by “4” and “7” on remote control) Check for firmware version and EEPROM
checksum.
· When entering into DOCTOR MODE, the firmware version and checksum data of EEPROM (if applicable) will appear on FL
display. Below is the information on the EEPROM IC (ROM correction) under 3 possible situations:
1. In the case that the correction point existence data is other than 0 (ie. correction file exists), EEPROM checksum display for
the microprocessor shall be made after calculating checksum by summing up the content of data area from EEPROM IC.
2. In the case when no EEPROM IC is installed. It is display as below (no display of checksum data)
3. In cases that the filename is different even though a EEPROM is installed, or no correction file exists, [NG] shall be displayed
(the correction point existence data is set to 0 at this condition).
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SA-AK750E / SA-AK750EB / SA-AK750EG

Note: Microprocessor firmware refers to version number for microprocessor IC located on PANEL P.C.B.. It is subject to change
which would be updated accordingly. ROM correction checksum refers to the HEX code that is displayed upon key buttons pressed
if an EEPROM is loaded in the unit.
9.3. Reliability Test Mode (CRS1 Mechanism)
Below is the process flow chart of ageing for the CD changer unit. (CRS1)
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SA-AK750E / SA-AK750EB / SA-AK750EG