Valley FABRICATOR 251 Service Manual - Fabricator 251
8-2
August 22, 2008
FABRICATOR 251
SERVICE MANUAL
CONNECTOR JB
Terminal
JB-1
wiper of wire speed control potentiometer,
varies between <2V to approximately 4.7VDC
(pot wiper)
reference
JA-5 or JB-5
Terminal
JB-2
wire speed control potentiometer minimum
(pot low) approximately 2VDC
reference
JA-5
Terminal
JB-3
wire speed control potentiometer maximum
approximately 4.7VDC
reference
JA-5
Terminal
JB-4
32VAC supply from auxiliary winding on fan
reference
JA-5 or JB-5
Terminal
JB-5
PCB common. Return for 32VAC supply from
auxiliary winding on M1
Terminal
JB-6
Motor positive terminal 0VDC - 24VDC with
speed pot
reference
JB-8
Terminal
JB-7
negative welding output voltage
reference
JB-9
Terminal
JB-8
Motor negative terminal 0VDC to -24VDC with
speed pot
reference
JB-6
Terminal
JB-9
positive welding voltage
Terminal
JB-10
return for 32VAC supply from auxiliary winding
on M1
reference
JB-5
Terminal
JB-11
relay contact to control SOL1 & W1
closes to complete circuit to JB-10
reference
JB-4
CONNECTOR JB
Torch circuit jumper installed
8.02 Circuit Operation Of The MIG Timer
PCB 7977965
This board is connected by way of a 6-way cable and
does not have any terminals available to measure.
8.03 Circuit Operation Of The Digital
Volt/Amp PCB 704883
Terminal
X13/1
24VAC supply for board
measure 24VAC wrt X13/3
Terminal
X13/2
no connection
Terminal
X13/3
24VAC supply for the board
measure 24VAC
wrt X13/1
Terminal
X13/4
PCB common, weld volts negative
shunt negative PCB 0V
Terminal
X13/5
shunt positive
measure a few hundred mV
wrt X13/4 when welding output is loaded
Terminal
X13/6
weld volts positive
measure welding output voltage
wrt X13/4