Test Procedures - Marconi LORAIN RHM800E50 Manual

refer to that particular test procedure in this section for
further troubleshooting information.
7.0 Semiconductor device outlines for diodes and
ure 7-l The outlines are intended to aid servicing per-
sonnel in identifying semiconductor terminations during
troubleshooting or replacement procedures.

Test Procedures

7.9 The following test procedures are those refer-
enced by number on the fault isolation chart. By follow-
ing one of the appropriate procedures, the servicing
technician can perform a test on components suspected
of failure. or on the rectifier to verity an operating condi-
tion. In the operational test procedures, appropriate
cautionary statements are inserted where necessary.
The servicing tedmician must observe the contents of
each statement and follow cormal precautionary proce-
dures necessary when servicing electronic equipment
to minimize the possibility of accidental electrical shock.
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7.10 Test Procedure 1. Perform this test when check-
ing a capacitorfor opens or shorts.
Place the POWER switch to the OFF posi-
tion. Insure that the external AC disconnect
is opened and the BATTERY DISCONNECT
link is removed.
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Allow at least 60 seconds to elapse from
time of rectifier shutdown, then disconnect
both leads or terminals of the capacitor to be
tested.
Set the digital muitffeter (DMM) for ohmme-
ter function, using a high resistance range.
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Momentarily short the capacitor leads or ter-
minals to insure complele diiarge. Con-
I nect meter test leads to capacitor leads or
terminals. and observe indicated resis-
tance. For a good capacitor without any
1
increases as capacitor takes a charge. Final
resistance is usually several hundred thou-
sand ohms, approaching 1 megohm. Initial
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high resistance appmaching infffky indf-
ued low resistance near zero ohms indicates
a shorted capacitor. Replace any capacitor
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which indicates an open or shorted condi-
tion.
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Perform Steps b) through d) on all capaci-
tors suspected of being faulty.
When all tests are completed. insure that
wiring to subject capacitors is properly con-
nected.
If no further tests are required, return recti-
fier to normal operation. Refer to Test Pro-
cedure 8 for the startup procedure.
7.11 Test Procedure 2, Perform this test when check-
ing a diode for opens or shorts.
Place the POWER switch to the OFF posi-
tion. Insure that the external AC disconnect
is opened and the BATTERY DISCONNECT
link is removed.
Disconnect all wiring from one terminal of
the diode to be tested.
Set the DMM for ohmmeter function, using
2K resistance range.
Connect meter test leads to diode terminals,
and note indicated resistance. Reverse test
lead connections, and again note indicated
resistance. A good diode without any faults
indicates a low resistance, typically 0.7K
ohms when forward biased, and nearly infi-
nite resistance when reverse biased. A
shorted diode typically indicates zero ohms
regardless of test lead connections: con-
versely, an open diode indicates very high
resistance regardless of test lead connec-
tions. Replace any diode which indicates an
open or shorted condition.
Perform Steps b) through d) on all diodes
suspected of being fautty.
When all tests are completed, insure that
nected.
If no further tests are required.
return rectifier to normal oparatiin. Refer to
Test Procedure 8 for the startup procedure.
7.12 Test Procedure 3. Perform this test when check-
ing continuity of extended voltage reference leads.
a) Place the POWER swlch to the OFF posi-
tion. Open the meter and control panels and
locate TB3 on circuit card A9.
Section 4387
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