Specifications
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SECTION 5 MACHINE TESTING / TROUBLESHOOTING / SERVICE
5.8.6 Arc On Circuit
The Arc On circuit consists of IC4 and IC5 and their immediate supporting components. The input from
the shunt is routed to the PCB control board module via Plug 6, pins 10 and 11 (P6-10, P6-11). The shunt
circuit develops 75mV per amp, which it sends to the shunt amplier. The shunt amplier is set to re
the arc on circuit with as little as 5 amps of cutting torch draw (0.375 Volts from the shunt). This output is
routed to IC2, as I ARC, and to a pair of inputs of IC5. The pin 12 input triggers the K3 relay via IC5 pin 14.
This is not utilized on the PC650.
The I ARC signal routed to pin 18 of IC2 is what turns o the HF relay, PCB1 K1, from the control board
internally.
CONTENTS