Miller Millermatic 251 Technical Manual page 21

4
Fan
Control
Relay CR1
Contactor W
6 6
Burden
Capacitor
Resistor
Bank C5
R1
19
14 15
Voltage
Wire Speed
Control R2
Control R3
16
Gun Trigger
Receptacle
RC1
Millermatic 251
7 8
Stabilizer Z1
Positive (+)
And Start
Output
Winding
Terminal
8
Negative (−)
Reed
Output
Relay
Terminal
18
Meter
Board
PC2
17
10-Pin
Spool Gun
Receptacle
RC7
10 Thermistor T
If unit overheats, PC1 disables unit
stopping all weld output.
11 Gas Valve GS1
Controlled by circuitry on main
control board PC1.
12 Circuit Breaker CB1
CB1 Protects wire drive motor PM
and spool gun motor circuits.
13 Wire Drive Motor PM
Feeds wire at a speed set by R3.
14 Wire Speed Control R3
Selects wire speed.
15 Voltage Control R2
Selects weld output voltage level.
16 Gun Trigger Receptacle RC1
7
Connects gun trigger circuit to
Wire
welding power source.
Drive
Assembly
17 Receptacle RC7
Electrode
Connects optional Spoolmatic 30A
welding gun.
18 Meter Board PC2
Voltmeter, Wire Feed Speed meter,
and HELP message displays.
Work
19 Reed Relay
Senses weld current and changes
mode from start to weld.
AC Or DC Control Circuits
1
Weld Current Circuit
φ
Power
TM-1326 Page 19