Yamaha MU128, Service Manual

MU128

18

Preparations
The following measuring instruments and jigs are
required for testing the equipment
Measuring instruments:

Low-frequency oscillator (Distortion factor:
0.1 % or less), Frequency counter,
Oscilloscope (Input impedance: 1 M

Ù

 or

more), Level meter (JIS-C curve), Analog
currugated analyzer, Keyboard amplifier

Jigs:

MIDI cable, PB (plug-in board)

Test

number

Test title

A

TEST ENTRY

B

STARTING THE TESTS

1

SRAM

2

BATTERY

3

LCD DOT BLINK AND CONTRAST

4

LED

5

SWITCHES

6

DIAL

7

MIDI 1 A Front

8

MIDI 2 A Rear

9

MIDI 3 B

10

MIDI 4

11

HOST SELECT

12

TO HOST

13

WAVE ROM

14

1  k Hz  O U T P UT   (L )  S IG N AL   S O U N D

15

1  k Hz O U T P UT  (R ) SIG NA L  SO U ND

16

A/D INPUT HIGH

17

A/D INPUT LOW

18

SDP AND DRM

19

C HE C KIN G   T HE   1 2 8  S IG N AL   S O U N DS

20

PB1 NAME

21

PB1 RAM

22

PB1 MIDI IN

23

PB1 MEL

24

PB2 NAME

25

PB2 RAM

26

PB2 MIDI IN

27

PB2 MEL

28

PB3 NAME

29

PB3 RAM

30

PB3 MIDI IN

31

PB3 MEL

32

FACTORY SETTINGS

33

EXIT

Note 1: For tests 20 to 23, the plug-in board should be

connected to the CN5 of the DM sheet on the
equipment before turning ON the power supply.

Note 2: For tests 24 to 27, the plug-in board should be

connected to the CN4 of the DM sheet on the
equipment before turning ON the power supply.

Note 3: For tests 28 to 31, the plug-in board should be

connected to the CN1 of the DM sheet on the
equipment before turning ON the power supply.

The tests shown below need not be conducted as
part of the inspection of MU128.

21  PB1 RAM
25  PB2 RAM
29  PB3 RAM

A. TEST ENTRY
To turn ON the equipment, press the STAND BY/ON
button while pressing the PLAY and MUTE/SOLO
buttons at one time.

MU128 TEST MODE
Ver#.## ##-###-##

Ver #.## shows the version number of the product
program ROM.

Precautions before starting the test
Before starting a test immediately after the end of the
assembly or battery replacement, press STAND
BY/ON while pressing the UTIL and ENTER buttons
at one time.  This step will change the inputted
values over to the factory settings.

B.

Starting the tests

Press the SELECT   /   button and select the test
numbers desired. Then press the ENTER button.  The
tests with their numbers selected will be then conducted
in sequence.
When the ENTER button is pressed without any test
numbers selected, the tests listed will be conducted in
numerical order, starting with the "1. SRAM " test.
When the test being conducted is finished without any
problems, ok will appear and the next test will be
conducted automatically.  If the next test is not
conducted automatically, refer to "Ending the test" for
each item.
The screen for selecting the test number desired will be
indicated by pressing the EXIT button, whether the
equipment fails in the test being conducted or not.)

If an error occurs during the "5.SWITCHES" test,
however, refer to "Ending the test".

1. SRAM

01  RAM
 

Write/read the data in the SRAM field and check/verify
the data.
All the SRAM data will be saved.

Displaying the test result

OK

01  RAM
                                ok

NG

01  RAM
                                err

2.

BATTERY

02  BATTERY

The battery voltage is checked by the A/D of the CPU (IC
21).    Make sure that the voltage is in the range from 2.9
to 3.4 V.
Displaying the test result

OK

02  BATTERY
                                ok