Lincoln Electric SQUARE WAVE TIG 355 Service Manual page 103

F-51
CONTROL TRANSFORMER (T5) VOLTAGE TEST (continued)
6. Check fuse F1 (0.5 amp). Test the resistance
from 6J15, on the feed-thru PC board, to the
#265 lead at the control transformer.
check the resistance from 7J15, on the feed-
thru PC board, to the #266 lead at the control
transformer.
A. If zero ohms resistance is shown, the test
is OK. Proceed to the feed-thru PC board
continuity test.
B. If resistance of any value is shown, check
wires and connections.
7. Test for the correct AC voltages at Plug P4.
See Figure F.14.
A. If one or more voltages are missing or
incorrect, the control transformer is faulty.
Replace.
B. Also check for 24VAC at the two black
leads going to 1J16 on the feed-thru PC
board and 1J9 on the control PC board.
TROUBLESHOOTING AND REPAIR
FIGURE F.14 – PLUG P4 DETAILS
BLACK
LEADS
Also
SQUARE WAVE TIG 355
IMPORTANT: If the control transformer is
replaced, refer to the label on the new transformer
for correct primary lead connections. If connected
wrong, the machine will have no OCV output. If no
OCV occurs, reverse the control transformer pri-
mary connections and recheck machine OCV.
NOTE: If input voltage varies, control transformer
voltages will vary accordingly.
CONTROL TRANSFORMER (T5)
VOLTAGE TEST CHART
Secondary Lead
Colors Plug P4 Pins
Yellow to Yellow 1 to 2
Blue to Blue 4 to 6
White to Blue 5 to 6
Red to White 10 to 5
Red to Red 10 to 12
F-51
Approximate
Voltages
10VAC
32VAC
16VAC
18VAC
36VAC