Lincoln Electric SVM188-A Service Manual page 50

F-10
PC BOARD TROUBLESHOOTING GUIDE (continued)
LED5
LED6
FIRING BOARD
1. With DC-600 set for the Test Conditions all ten
LEDs on the Firing Board should be lit.
2. LEDs 7, 8 & 9 indicate that the three 34vac sup-
plies from the Main Transformer are present on the
Firing Board. They should all be ON whenever the
Power Switch is ON.
• If any are not ON check the voltages at P5
LED that Check AC voltage between pins specified,
was off it should be approximately 34VAC .
7 P5 pins 15 & 16 (wires 203,204)
8 P5 pins 7 & 8 (wires 205,206)
9 P5 pins 5 & 6 (wires 207,208)
• If voltage is present and the LED is OFF, replace
the Firing Board
3. LED 10 indicates that the machine is "triggered"
(Output Terminal Switch ON).
• Alternate Trigger Methods:
Operate Wire Feeder trigger.
Place a jumper across 2 & 4 on T.S.2.
Jumper between pins C & D of 14 pin connector.
• If LED 10 does not come ON, check wiring.
Perform the Internal Trigger Circuit Test.
TROUBLESHOOTING AND REPAIR
FIGURE F.1 – FIRING BOARD LEDs
LED8 LED9
LED3
LED4
G3742-[ ]
DC-600
LED7
LED1
LED10
LED2
FIRING BOARD
4. LEDs 1 thru 6 indicate that gate signals are being
sent to the SCRs in the Main Rectifier. These
LEDs will vary in brightness as the Output Control
is changed.
• It is important that all six LEDs are the same bril-
liance as each other.
If none are lit, check the voltage at lead 231
(P5 - Pin13). See the Control Board Test. If
OK, Replace the Firing Board.
If LEDs are not the same brilliance, see the
SCR Bridge Test and check the connections
to J-4. If OK, replace the Firing Board.
F-10
J5
(205) 8
16 (204)
(206) 7
15 (203)
(207) 6
14
(208) 5
13 (231)
4
12 (215)
3
11
2
10
1
9
J6
J7
J8
J4