Valley FABRICATOR 251 Service Manual - Service Manual
August 22, 2008
7-7
SERVICE MANUAL
FABRICATOR 251
7.09 Logic and Control Problems
A. Nothing happens when gun switch is depressed;
No gas flow, contactor does not energize, feed
rolls do not turn. TEMPERATURE LED is on.
1. Unit overheated.
a. Allow unit to cool
2. Insufficient airflow around / through unit.
a. See installation section 3.02 for clearance
requirements
3. Open Thermal Protection Switch TS1 or TS2
a. Check continuity on the MAIN PCB JA
connector between pins 5 & 7 and if open check
the switches TS1 & TS2 individually and replace
the defective switch.
B. Nothing happens when gun switch is depressed;
No gas flow, contactor does not energize, feed
rolls do not turn. TEMPERATURE led is off.
1. MIG GUN / SPOOL GUN SELECTOR SWITCH SW2
is in SPOOL GUN position
a. Set SW2 to MIG GUN position
2. Defective SW2
a. Check continuity of SW2.
3. Defective gun switch
a. Check continuity of gun switch
4. Open wires between gun receptacle and MAIN PCB
(PCB 1)
a. Measure between JA-1 to JA-2 at the Control
PCB for approx 40 VDC when switch is open
and then drops to 0 VDC when gun switch is
closed. If it does not drop check continuity of
the wires.
5) Faulty Fan/Aux. transformer assembly M1
a. With Gun Switch depressed, measure for approx
30 VAC between the brown (#30) and orange
(#31C). If low or not present, replace M1.
6. Faulty MAIN PCB (PCB 1)
a. Measure at PCB 1 between JB-5 to JA-1 for
40VDC. If voltage is not present, replace PCB-1
7). Faulty MIG TIMER PCB (PCB 2)
a. See Section 7.15
8. Faulty MAIN PCB 1
a. Measure between JB-4 to JB-11 at PCB 1 for
approx 30 VAC when gun switch is closed. If
voltage is not present, replace PCB.
9. Faulty SPOOL GUN PCB (PCB 3)
a) Measure at PCB1 between JB-5 to JA-2 for
21VDC. If voltage is not present, replace PCB3
C. When gun switch is closed, gas flows, contactor
does not energize, feed roll does not turn.
1. Defective Contactor W1
a. Measure for 30VAC on the contactor coil
between White wire (#31C) and white wire
(#32A). If voltage is present replace W1.
D. When Gun Switch is closed, no gas flows but
contactor closes and feed rolls turn.
1. Gas supply not connected or turned on
a. Verify gas supply to unit is correct and
connected to the gas inlet labeled:
2. Defective Gas Solenoid SOL1
a. With gun switch closed, measure for 30VAC
on the gas solenoid between Orange wires
(#31A & 31B) and Blue wire (#33). If voltage
is present replace gas solenoid.
3. Defective MIG GUN / SPOOL GUN SELECTOR
SWITCH SW2
a. With gun switch closed, measure for 30VAC
on the gas solenoid between Orange wires
(#31A or 31B) and Blue wire (#33). If voltage
is not present, check SW2.
E. When Gun Switch is closed, gas flows, contactor
closes, display shows 15 volts, but feed rolls do
not turn
1. CB2 5 amp Circuit Breaker tripped
a. Reset CB2
2. Defective WIRE FEED MOTOR M2
a. With Gun Switch closed, measure for approx
2-16 vdc variation at the control PCB between
JB-6 to JB-8 as the WIRE SPEED CONTROL
potentiometer is varied from minimum to maxi-
mum. If voltage is correct, replace motor.