TROUBLESHOOTING
TESTING AND ADJUSTING
POSSIBLE CAUSES
VERIFICATION PROCEDURE
(Continued)
resistance will be seen. As a charge from the ohmmeter is put on
the capacitor the resistance will increase to a constant reading. Set
ohmmeter scale to RX1000. For more information, see TESTING
POWER RECTIFIERS AND CONTROLLED RECTIFIERS.
13. Loss of Residual Magnetism
Check AC voltage at terminals (20) and (22) of regulator
assembly. Less than 4 to 5 volts at 50 hertz or 8 to 9 volts at 60
hertz is an indication that residual magnetism has been lost.
See FLASHING THE FIELD.
14. Controlled Rectifier (CR9) Has
Disconnect controlled rectifier (CR9) by removing connections at
a Defect
spade terminals (10, 11 and 19) of rectifier module (A2). The
ohmmeter scale must be on RX1000. Check forward and reverse
resistance of (CR9) by connecting the positive cable of the meter
to spade terminals (11) and the negative cable to terminal (19).
Read the value of resistance. Reverse the cables and read the
resistance again. Typical resistance in both directions is 300.000
ohms. NOTE: Controlled rectifier (CR9) is connected in parallel
with resistance-capacitance circuit in rectifier module (A2). When
the ohmmeter test cables are first connected to the circuit, a low
resistance will be seen. As a charge from the ohmmeter is put on
the capacitor the resistance will increase to a constant high
indication.
Check the continuity of the gate to cathode circuit of (CR9).
Connect the positive cable of ohmmeter to spade terminal 10,
and the negative cable to spade terminal (11). Typical resistance !s
10 to 200 ohms.
The gate circuit can be checked with the continuity tester
(8S4627). Connect the positive cable to spade terminal (191 and
the negative cable to spade terminal (11). There must be no light
or meter indication. Place a separate wire connection between
spade terminals (19) and (10). Remove the wire connection as
soon as the light comes on. The light will be on until the
connection at either terminal (19) or (10) is broken. This is a test
of the ability of (CR9) to "turn on." For more information, see
TESTING POWER RECTIFIERS AND CONTROLLED RECTI-
FIERS.
15. Rectifier Module (A2) Has a
Disconnect rectifier module (A2) by removing the wires on spade
Defect
terminals (6, 8, 10, 11 and 19). Check the continuity of the
connections inside of (A2) with an ohmmeter or 8S4627
Continuity Tester.
Check the following:
FROM
TO
Spade Terminal (19)
Heat Sink (E3)
Spade Terminal (11)
Cathode terminal of (CR9)
Spade Terminal (10)
Gate terminal of (CR9)
Cathode terminal of (CR9)
Heat Sink (E4)
Spade Terminal (6)
Anode terminal of (CR10)
Spade Terminal (8)
Heat Sink (E4)
(Continued on next page)
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