Lincoln Electric PRO-CUT 55 SVM140-A Service Manual page 82

F-45
LOW VOLTAGE CIRCUIT TEST (continued)
T2 AUXILIARY
TRANSFORMER
TO H1
H1
"C" TERMINAL
INPUT
RECTIFIER
H2
H3
TO
RECONNECT
LEAD "A"
H4
H5
PROCEDURE
1. Remove input power to the Pro-Cut 55
machine.
2. Using the 5/16" nutdriver remove the case
wraparound cover.
ELECTRIC SHOCK
• Do not touch electrically hot parts.
3. Apply the correct input power to the machine
and carefully check for the following voltages.
4. Check for the presence of approximately 28
VDC on the output board.
a. LED1 should be lit when 28 VDC is present.
See Figure F.13. See Output Board LED
Definitions and Figure F.12, Low Voltage
Circuit Diagram.
b. To verify the presence of 28 VDC, check
across capacitor C13. Make certain the
voltmeter probes make good contact with
the capacitor leads. See Figure F.13.
TROUBLESHOOTING & REPAIR
FIGURE F.12 - LOW VOLTAGE CIRCUIT DIAGRAM
BROWN
8
12VAC
BROWN
3
RED
2
24VAC
RED
6
BLUE
4
18VAC
WHITE
5
18VAC
BLUE
9
J21
WARNING
can kill.
PRO-CUT 55
#53
3J30
=17VDC
#56
6J30
PLASMA
OUTPUT
#51
BOARD
1J30
=28VDC
#54
4J30
#61
1J1
6J2
=+15VDC
#62
2J1
CONTROL BOARD
=-15VDC
9J2
#64
4J1
5. Check for the presence of 17 VDC on the out-
put board.
a. LED2 should be lit when 17 VDC is present.
See Figure F.13. See Output Board LED
Definitions and Figure F.12, Low Voltage
Circuit Diagram.
b. To verify the presence of 17 VDC, check
from plug J31 Pin-6 to diode D25 (anode).
See Figure F.13. Make certain the volt-
meter probes make good contact with pin-
6 and the diode anode lead.
6. Check for the presence of +15 VDC on the
control board.
a. LED1 should be lit when +15 VDC is pre-
sent. See Figure F.13.
Board LED Definitions and Figure F.12,
Low Voltage Circuit Diagram.
7. Check for the presence of -15 VDC on the con-
trol board.
a. LED3 should be lit when -15 VDC is pre-
sent. See Figure F.13.
Board LED Definitions and Figure F.12,
Low Voltage Circuit Diagram.
F-45
D
#216
I B
15J40
+
S O
+15VDC
P A
#219
10J40
L R
A D
Y
See Control
See Control