Valley FABRICATOR 251 Service Manual - Service Manual
August 22, 2008
8-1
SERVICE MANUAL
FABRICATOR 251
SECTION 8:
CIRCUIT OPERATION
CONNECTOR JE
Burnback potentiometer
100k potentiometer between pins
Terminal
JE-1
burnback potentiometer 0VDC
reference PCB common
Terminal
JE-2
burnback potentiometer approx 13VDC when
trigger on
ramps down to zero after trigger is released
reference JA-5
8.01 Circuit Operation Of The Control PCB 7977964
Power Supply
24VAC is taken from the auxiliary wiring of the fan. This voltage is then connected to the PCB 7977964 where it is half
wave rectified and filtered. This voltage is then fed to a zener regulator to provide the +15VDC supply for the electronics
on the circuit board
Inputs to the Control PCB
CONNECTOR JA
Terminal JA-1
trigger input=40VDC trigger open, approx 20VDC
trigger closed
reference JA-5
Terminal JA-2
trigger input=0VDC trigger open, approx 20VDCV
trigger closed
reference JA-5
Terminal
JA-3
spot timer pot=12VDCV trigger closed 0VDC
trigger
open
reference JA-5
Terminal
JA-4
spot timer pot= ramps up to 12V from 0V when
trigger closed
0VDC when trigger open
reference JA-5
Terminal JA-5
PCB common
Terminal JA-6
over temperature LED anode = approx 2VDC when
overtemp led is ON, 0V when off
reference JA-5
Terminal JA-7
over temperature switch=0VDC temp switch
closed, approx 15VDCV switch open
reference JA-5