Lincoln Electric V205-T service manual Figure F.5 Input Filter Board

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F-17 F-17

TROUBLESHOOTING & REPAIR

INPUT FILTER BOARD TEST (continued)

FIGURE F.5 INPUT FILTER BOARD

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Note 1: A varistor ZN1 is placed between the two power supply phases, so if an instantaneous voltage in excess of 275VAC appears on ter- minals RV1 & RV2, the varistor very rapidly becomes conductive and thus absorbing a current peak sufficient to limit the above said overvoltage; this way the varistor ZN1 pro- tects 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 atmospheric lightening strikes. However, if over-voltage is high and prolonged, the varistor cannot dissipate this high energy and fails. For example, the machine is improperly connected to 275VAC, or the over-voltage is caused by non stabilized power units of inadequate capacity.

Note 2: The radio noise suppression circuit has two purposes: to keep the machine’s radio fre- quency emisions within limits specified by standards and to ensure the machine’s immu- nity against the same type of problems caused any electronic devices connected to the same power supply source. The filter con- sists of a network of capacitors, some of which are grounded, and a toroidal inductor.

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V205-T AC/DC