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TROUBLESHOOTING AND REPAIR | ||
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INPUT FILTER BOARD TEST (continued)
FIGURE F.5 – INPUT FILTER BOARD
INPUT FILTER BOARD
POWER SUPPLY “IN” 230V (115V)
RV1 RV2
PZ1 PZ2
“PE”
EARTH CONNECTION
CN | CN |
230V (115V)
POWER SUPPLY “OUT” 230V (115V) VAC 2.3V (1.2V)
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NOTE 1: A varistor ZN1 is placed between the two power supply phases, so if an instanta- neous voltage in excess of 275VAC appears on terminals RV1 & RV2, the varistor very rapidly becomes conductive and thus absorbing a current peak suffi- cient to limit the above said overvoltage; this way the varistor ZN1 protects the other parts of the machine from energy- limited overvoltages. This process has no destructive effect on the component if the energy generated by the voltage peak is low, as in the case of atmospher- ic lightening strikes. However, if over- voltage is high and prolonged, the varis- tor cannot dissipate this high energy and fails. For example, the machine is improperly connected to 275VAC, or the
NOTE 2: The radio noise suppression circuit has two purposes: to keep the machine’s radio frequency emissions within limits specified by standards and to ensure the machine’s immunity against the same type of problems caused any electronic devices connected to the same power supply source. The filter consists of a network of capacitors, some of which are grounded, and a toroidal inductor.