Lincoln Electric R3R 500-I, R3R 375-I manual Checking Current Control Rheostat on Machine

E-9 TROUBLESHOOTING E-9

(high resistance value). This indicates that the capacitor in the snubber circuit is taking a charge.

3.If the needle stays to the right, the capacitor is shorted and the assembly is defective.

4.If the needle does not move, the capacitor is open and the assembly is defective.

G.CHECKING CURRENT CONTROL RHEOSTAT ON MACHINE

1.Turn machine off.

2.Remove the control panel screws and open the front cover.

3.Turn the current control switch to remote.

4.Disconnect the harness plug from the control board.

5.Put current range switch to B range.

6.With an ohmmeter on X1K, connect it to lead 210 and 211 on SW #2. Rotate the current con- trol rheostat. The resistance reading should be from around zero to 10K ohms. Check the resis- tance reading between 75 on the terminal strip (codes below 9500) or Amphenol (codes above 9500), and 211 on SW #2. The reading must be 10K ohms. No reading will indicate an open rheostat and low reading will indicate a shorted or partially shorted rheostat; in either case, replace.

H.TOGGLE SWITCH CHECK

1.Turn off the machine power input. SW-1 has 110 volts across it when the input power is connect- ed.

2.Isolate the switch to be tested by removing all connecting leads.

3.Check to make sure the switch is making con- nections with a VOM meter. The meter should read zero resistance.

4.Put the ohmmeter on X1K scale and measure the resistance between the terminal and the case of the machine (touch a self-tapping screw). Reading should be infinite.

5.If either step (3) or step (4) fails, replace the switch.

I.REMOTE CONTROL CHECK

For codes above 9500, the remote control Amphenol pin assignments are: pin C-75, pin B-76, and pin A-77. Disconnect the remote field control and connect an ohmmeter across 75 and 76 and rotate the rheostat in the remote control. The resis- tance reading should go from zero to 10K ohms. Repeat with triplet across 77 and 76 with same results. Connect ohmmeter across 75 and 77. The reading should be 10K ohms. A lower reading will indicate a shorted or partially shorted rheostat. A very high reading will indicate an open rheostat. In either of the last two cases, replace rheostat. Check cable for any physical damage.

J. POWER RECTIFIER BRIDGE ASSEM- BLY CHECKING PROCEDURE

CAUTION

The rectifier bridge tests outlined below will iden- tify the most common effects found in power diodes or power silicon controlled rectifiers. If a bridge problem still exists after test, please call a Lincoln Field Service Shop. Further evaluation of diodes or silicon controlled rectifiers may require laboratory equipment.

1.DEVICE ISOLATION (see the instruction manu- al Parts List for the exact location)

Disconnect the following leads from the bridge, shown in Diagram 1:

a.Wiring harness gate leads (G1, G2, G3) from the gate lead terminals(1) on the Control PC board.

b.AC leads X1, X2 and X3 from the anodes of the SCR’s and cathodes of the diodes.

c.The 220, 221 and 223 leads from the Snubber PC board.

d.Lead 220 that connects to the latching resis- tor (R3).

e.The cathode of each diode (4 total).

(1)Connector J4 on latest control board.

IDEALARC® R3R 375-I, 500-I AND 600-I