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and 

ORDER No. MQM1505001V2 

 

There are special components used in this equipment which are important for safety. These parts are marked       in the  
Schematic Diagrams, Circuit Board Diagrams, Explorer Views and 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. 

TX-24CR300/TX-40CR300/ 

TX-48CR300

1 

 

SAFETY PRECAUTIONS ........................................... 2 

 

GENERAL GUIDE LINES ...................................... 2 

 

TOUCH – CURRENT CHECK ............................... 2 

PREVENTION OF ELECTROSTATIC DISCHARGE 

(ESD) TO ELECTROSTATICALLY SENSITIVE (ES) 

DEVICES .................................................................... 3 

ABOUT LEAD FREE SOLDER (PBF) .........................  4 

SERVICE NAVIGATION ............................................. 5 

SERVICE HINTS ........................................................ 7 

 

 

 

 

 

 

 

 

 

 

 

 

 

SERVICE MODE FUNCTION ..................................... 9 

SOFTWARE UPDATE   ............................................ 10 

HOTEL MODE .......................................................... 11 

PARTS LOCATION ...................................................  14 

LOCATION OF LEAD  WIRING ................................ 15 

BLOCK DIAGRAM .................................................... 19 

EXPLODED VIEW .................................................... 20 

  

2 

 

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, see to it that all the protective devices such as insulation barriers, insulation papers shields are properly 

installed. 

3.  After servicing, make the following touch current checks to prevent the customer from being exposed to shock hazards. 
 
 
 

1.  Plug the AC cord directly into the AC outlet. Do not use an isolation transformer for this check. 
2.  Connect a measuring network for touch currents between each exposed metallic part on the set and a good earth 

ground such as a water pipe, as shown in Fig. 2. 

3.  Use Leakage Current Tester (Simpson 228 or equivalent) to measure the potential across the measuring network. 
4.  Check each exposed metallic part, and measure the voltage at each point. 
5.  Reserve the AC plug in the AC outlet and repeat each of the above measure. 
6.  The potential at any point (TOUCH CURRENT) expressed as voltage U1 and U2, does not exceed the following values: 

For a. c.: U1 = 35 V (peak) and U2 = 0.35 V (peak); 
For d. c.: U1 = 1.0 V, 

Note:

 

The limit value of U2 = 0.35 V (peak) for a. c. and U1 = 1.0 V for d. c. correspond to the values 0.7 mA (peak) a. c. and 
2.0 mA d. c. 
The limit value U1 = 35 V (peak) for a. c. correspond to the value 70 mA (peak) a. c. for frequencies greater than 100 
kHz. 

7.  In case a 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. 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

TO 
APPLIANCES 
EXPOSED 
METAL PARTS 

Resistance values in ohms (

) 

V 

R

0

=500

 

R

S

=1500

 

C

S

=0.22

F 

10k

 

0.022

F 

COLD 
WATER PIPE 
(EARTH GROUND)

 

V: Voltmeter or oscilloscope 
  (r.m.s. or peak reading) 

Measuring network for TOUCH CURRENTS 

Input resistance: 

1M 

Input capacitance:

200pF 

Frequency range: 15Hz to 1MHz and d.c.respectively 

NOTE – Appropriate measures should be taken to obtain the correct value in case of non-sinusoidal waveforms 

U

2

 (V) 

U

1

 (V) 

3 

 

 
Some semiconductor (solid state) devices can be damaged easily by static 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 electrostatic discharge (ESD). 
 
1.  Immediately before handling any semiconductor component or semiconductor-equipped 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 equipped with ES devices, place the assembly on a conductive surface such as 

aluminum 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 removal device. Some solder removal devices not classified as "anti-static (ESD 

protected)" can generate electrical charge sufficient 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, aluminum 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 bodily 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). 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

There are special components used in this equipment which are important for safety. 
These parts are marked by      in schematic diagrams, exploded views and 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.