Lincoln Electric IDEALARC DC-1500 Service Manual page 62

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FIRING BOARD TEST PROCEDURE (continued)
FIGURE F.8 – TERMINAL STRIP JUMPER WIRE CONNECTIONS
10. Rotate the output control potentiometer (R1).
As the potentiometer is turned clockwise, the
LEDs should glow brighter. As the potentiome-
ter is turned counter-clockwise, the LEDs
should dim.
a. If the LEDs glow and change in bright-
ness equally as the potentiometer is
turned and the problem continues, then
the SCR bridge may be faulty. Perform
the SCR Bridge Test.
b. If any or all of LEDs 1 through 6 do not
glow, or do not change in brightness
equally as the potentiometer is turned,
continue to next step.
c. If one or two LEDs stay bright or dim
while the others change, this could indi-
cate either an open or shorted gate or a
faulty snubber on the related SCR
snubber assembly. Perform the SCR
Bridge Test.
11. Locate and test for 6 to 15 VDC between leads
#231 and #214 on the Firing Board in the CV
mode. When the output control potentiometer
(R1) is rotated, the DC voltage between leads
#231 and #214 should vary from 6 to 15 VDC.
TROUBLESHOOTING AND REPAIR
(Located under small door at front left of machine)
IDEALARC® DC-1500
12. If an LED continues to be lit and should not be,
a circuit may be faulty on the Firing Board
between a Molex plug and LED. Replace
Firing Board.
13. If the DC voltage does NOT vary, as poten-
tiometer (R1) is rotated, the Control Board may
be faulty.
14. Locate and test for approximately 5.8 VDC
between leads #231 and #214 on the Firing
Board in VV (CC) mode. When the output con-
trol potentiometer (R1) is rotated, the DC volt-
age between leads #231 and #214 should
NOT vary and should remain at a constant
approximate 5.8 VDC.
NOTE: The DC voltage may vary slightly at the
lower portion of the range.
F-28