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TROUBLESHOOTING & REPAIR
CURRENT BALANCE TEST (continued)
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TEST PROCEDURE
1.Turn the engine off.
2.Perform the Case Cover Removal Procedure and tilt the control panel out.
3.Locate plug J3 at the control board and P15 in the main harness. See Figure F.29.
4.Disconnect P15.
WARNING
ELECTRIC SHOCK CAN KILL.
•Do not touch electrically live parts such as output terminals or internal wiring.
•Insulate yourself from the work and ground.
•Always wear dry insulating gloves.
5.Start the machine.
6.In CC mode, load the machine on a load grid to 375 amps at 34 VDC.
7.Immediately after applying the load, use a voltmeter to measure (one at a time) the volt- age from each chopper heat sink to the posi-
tive weld stud. Each voltage measurement should
8.A voltage out of spec indicates a possible blown IGBT chopper module and the chopper boards must be replaced. Replace both chop- per boards using the POWER MODULE (CHOPPER) PC BOARD REMOVAL AND REPLACEMENT PROCEDURE.
9.A voltage within spec indicates that the chop- per modules are sharing weld current relative- ly equal and the chopper boards are ok.
10.Remove the load and turn off the engine.
11.Disconnect J3 at the control board. See
Figure F.29.
12.Using a pair of wire cutters, cut leads 68 and 69 from the #3 and #4 cavities of plug J3. Butt tape and insulate loose ends. See Figure F.28.
NOTE: Cutting and removing these leads will help to eliminate intermittent lack of out- put problems.
13.Plug J3 back into the control board.
14.Using the CASE COVER REMOVAL AND REPLACEMENT PROCEDURE, install the control panel and side panels on the machine.
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FIGURE - F.28 PLUG J3
69
68
