Miller Electric S-21E - Manual (Page 24)

8-5. OPTIONAL SPOTIBURNBACK BOARD PC2
TESTING INFORMATION (Diagram 8-3 And
Figure 8-2)
WARNING: ELECTRIC SHOCK can kill. A
• Do not touch live electrical parts.
• Shut down wire feeder and welding power
source or stop engine before making or
changing meter lead connections and before
disconnecting or connecting any leads.
MOVING PARTS can cause serious Injury.
• Keep away from moving parts.
HOT SURFACES can cause severe burns.
• Allow cooling period before servicing.
This procedure requires the unit to be ener-
p
ized. Only qualified persons familiar with and
ollowing standard safety practices are to per-
form this testing procedure.
A CAUTION: ELECTROSTATIC DISCHARGE
(ESD) can damage circuit boards.
• Put on properly grounded wrist strap BE-
FORE handling circuit boards.
• Transport circuit boards in proper static-
shielding carriers or packages.
• Perform work only at a static-safe work area.
INCORRECT INSTALLATION or misaligned
plugs can damage circuit board.
• Be sure that plugs are properly installed and
aligned.
EXCESSIVE PRESSURE can
board.
Receptacle
RC4
SA-123 147-E
break circuit
• Use only minimal pressure and gentle move-
ment when disconnecting or connecting
board plugs and removingor installing board.
IMPORTANT: For all checks, be sure to testand verify
the continuity of leads between the board and the area
where check is performed. Allchecks shouldgo through
the connections and be actual terminal-to-terminal tests
so that bad connections or leads and corrosion are not
the problem.
A. Power Supply Circuit
Input power of +35 volts dc should be present between
pins A and B (DC circuit common) of receptacle RCl. If
+35 volts dc are not present, check that plug PLG51 is
secure in receptacle RCl on Burnback Board PC2 and
plug PLG 1 is secure in receptacle RCl on Motor Control
Board PCl. If +35 volts dc are still not present, check
Motor Control Board PCl according to Section 8-4.
B. Trigger Circuit
A trigger input voltage of +19 volts dc should be present
at pin D of receptacle RCl with respect to circuit com-
mon when the gun trigger is pressed, and 0 volts dc
should be present when the gun trigger is released. If
+19 volts dc are not present when the gun trigger is
pressed, check Motor Board PCi according to Section
8-4.
C. Motor StartlStop Circuit
When the gun trigger is pressed, a motor control output
voltage of +24 volts dc should be present at pin A of re-
S-2iE
Receptacle
RC3
Figure 8-1. Motor Control Board PCi Component Locations And Information
TM-i57i Page 20