Magnum CTV-2120 TXT Service Manual - page 2
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SAFETY INSTRUCTIONS
WARNING: BEFORE SERVICING THIS CHASSIS, READ THE "X-RAY
RADIATION PRECAUTION", "SAFETY PRECAUTION" AND "PRODUCT SAFETY
NOTICE" DESCRIBED BELOW.
X-RAY RADIATION PRECAUTION
1. Extremely high voltage of the picture tube may result in producing potentially hazardous X-RAY RADIATION. To
avoid such hazards, the high voltage must not be above the specified limit.
The nominal value of the high voltage of this receiver is about 25.9 kV at zero beam current (minimum brightness)
under 175-245V AC power source.
The high voltage must, under any circumstances, not exceed about 30.5 kV.
Each time this receiver requires servicing, the high voltage should be checked according to the HIGH VOLTAGE
CHECK procedure at the back of this manual. it is recommended to record the reading of the high voltage in the
service record each time. Using an accurate and reliable high i mpedance and high voltage meter is quite important.
Connect the NEGATIVE and POSITIVE probe of a high voltage meter to the "ground" and the high voltage anode
cap of the picture tube respectively.
HIGH VOLTAGE CHECK CONNECTION DIAGRAM
2. The only source of X-RAY RADIATION in this receiver is the picture tube. For ensuring the intensity of X-RAY
RADIATION from the picture tube being within the specified safety limit, the replacement picture tube must be
exactly the same type specified in the parts list.
3. Some parts in this receiver have special safety-related characteristics which would affect X-RAY RADIATION
protection. For safety, parts replacement should be carried out only after referring to the "PRODUCT SAFETY
NOTICE" below.
PRODUCT SAFETY NOTICE
Many electrical and mechanical parts in this receiver have special safety-related characteristics (directly relate to
high voltage, high temperature or electric shock) which are not easily seen by visual inspection. Whenever replacing
such components, make sure that the replacement parts can provide effective X-RAY RADIATION protection even
though their high voltage and wattage can meet the specification of the original design. Such parts can be identified by
shading and marking with
in the schematic diagram and the parts list.
Before replacing any of these components, read the parts list in this manual carefully. Using substitute parts which do
not have the same safety characteristics as the ones specified in the parts list may create excessive X-RAY RADIATION.
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C BUS CONCEPT
(1). Characteristics
1.1 I
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C Bus consists of clock (SCL) and data (SDA) lines.
1.2 It transmits data among integrated circuits in full duplex mode.
1.3 It is composed of a main IC chip (CPU) and one or more sub-IC chips.
l The CPU mainly operates data transmissions and also generates clock signal.
l The CPU also controls all sub-IC chips, making them work.
(2). I
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C Bus Application in this TV unit
High impedance and high voltagh meter
Chassis
Picture tube ground
Picture tube high voltage anode cap