Guardian 4389 Repair Manual page 42

SECTION 2.4
DIAGNOSTIC TESTS
27.Repeat Step 22 using stator lead Wire 33; Pin 3
28.Repeat Step 22 using stator lead Wire 33; Pin 7
29.Repeat Step 22 using Pin 1; Pin 3
30.Repeat Step 22 using Pin 1; Pin 7
31.Repeat Step 22 using Pin 3; Pin 7
TEST CONTROL PANEL WIRES FOR CONTINUITY:
32.Set a VOM to its "Rx1" scale.
33.Disconnect the C2 connector from the control panel. (C2
is the closest to the back panel). Refer to Figure 5 for
the pin locations (Male Side).
33.Connect one meter test lead to Pin 5 of the C2 connector
(Male Side), connect the other test lead to Wire 22 at the
voltage regulator. CONTINUITY should be measured.
34.Connect one meter test lead to Pin 6 of the C2 connector
(Male Side), connect the other test lead to Wire 11 at the
voltage regulator. CONTINUITY should be measured.
35.Connect one meter test lead to Pin 7 of the C2 connector
(Male Side), connect the other test lead to Wire 6 at the
voltage regulator. CONTINUITY should be measured.
36.Connect one meter test lead to Pin 8 of the C2 connector
(Male Side), connect the other test lead to Wire 2 at CB2
(DPE circuit breaker). CONTINUITY should be measured.
RESULTS:
1. Stator winding resistance values is a test of winding
continuity and resistance. If a very high resistance or
INFINITY is indicated, the winding is open or partially
open.
2. Testing for a "grounded" condition: Any upscale move-
ment of the meter needle or dial indicates the winding
is grounded.
3. Testing for a "shorted" condition: Any upscale move-
ment of the VOM needle or dial indicates the winding
is shorted.
4. If the stator tests good and wire continuity tests good ,
perform "Insulation Resistance Test" in Section 1.4.
5. If any test of wire continuity failed in control panel failed,
repair or replace the wire, terminal or pin connectors for
that associated wire as needed.
NOTE: Read Section 1.4, "Testing, Cleaning and
Drying" carefully. If the winding tests good, per-
form an insulation resistance test. If the winding
fails the insulation resistance test, clean and dry
the stator as outlined in Section 1.4. Then,
repeat the insulation resistance test. If the wind-
ing fails the second resistance test (after clean-
ing and drying), replace the stator assembly.
Page 40
PART 2
TEST 8 - RESISTANCE CHECK OF
ROTOR CIRCUIT
DISCUSSION:
To verify the zero current draw reading and measure
the rotor circuit.
PROCEDURE:
1. Disconnect Wire 4 from the voltage regulator. It is locat-
ed 3rd terminal from the top of the volt regulator.
2. Set VOM to the "Rx1" scale.
3. Connect one test lead to Wire 4. Connect the other test
lead to a clean frame ground. Note the resistance reading.
Compare to specifications in the front of this manual.
RESULTS:
1. If the resistance reading is correct, check your VOM
meters fuse and repeat Test 4.
2. If INFINITY is measured on your VOM meter, go to
Test 9.
TEST 9 - CHECK BRUSHES AND SLIP RINGS
DISCUSSION:
The function of the brushes and slip rings is to pro-
vide for passage of excitation current from stationary
components to the rotating rotor. Brushes are made
of a special long lasting material and seldom wear out
or fail. However, slip rings can develop a tarnish or
film that can inhibit or offer a resistance to the flow of
electricity. Such a non-conducting film usually devel-
ops during non-operating periods. Broken or discon-
nected wiring can also cause loss of excitation cur-
rent to the rotor.
Figure 6. Checking Brushes and Slip Rings
PROCEDURE:
1. Disconnect connector C2 (deutsch connector closest to
the back panel). Refer to Figure 5 in Section 2.4.
AC GENERATORS