46
TESTING HIGH VOLTAGE DIODES
High voltage diodes, such as those found in video high
voltage and focus voltage sections may require up to 200
volts before they are forward biased and begin to
conduct. They cannot be tested with an ohmmeter since,
with only a few volts applied, a good high voltage diode
will simply indicate open no matter how the ohmmeter is
connected.
The capacitor leakage test of the LC103 provides
sufficient voltage to bias high voltage diodes into
conduction and also to test them for reverse breakdown.
Test the diode for normal forward conduction first.
Then reverse the test leads and check for reverse
leakage.
Fig. 33: To test a high voltage diode, enough
voltage is needed to forward bias off the junctions.
———————— WARNING —————————
This test should only be performed by a person who
understands the shock hazard of up to 1000 volts
applied to the test leads when the CAPACITOR
LEAKAGE TEST button is depressed. DO NOT hold
the diode in your hand, or touch the test leads or
diode leads when making this test.
————————
ATTENTION
————————
Le LC103 est fait pour être utilisé par une personne
qui est techniquement capable et qui comprend les
chocs que peut produire l’équipement (jusqu’à 1000
V) lorsque le test de fuite est utilisé. NE PAS tenir la
capacité dans la main ou toucher la conde ou la
patter de la capacité pendant le test de fuite.
To test a high voltage diode:
1.
Connect the red test lead to the diode anode (“-” end)
and the black test lead to the diode's cathode (“+”
end).
2.
Enter 50 volts into the leakage supply and depress the
CAPACITOR LEAKAGE test button.
3.
If the LC103 display shows no leakage, apply more
voltage until the diode begins to conduct, as indicated
by a leakage current reading of 100 uA or greater.
4.
Once the diode begins to conduct, do not apply any
higher voltage as this will cause excessive current
flow through the diode and damage it.
5.
If you apply 999.9 volts to the diode and it still shows
no conduction, it is open and you do not need to
continue the test.
6.
When the diode begins to conduct, release the
CAPACITOR LEAKAGE button and reverse the test
lead connection to the diode.
7.
Set the leakage power supply to the PIV (peak
inverse voltage) of the diode shown in a replacement
guide. If the PIV is greater than 1000 V (as it will be
for most diodes) set the leakage power supply to
999.9 volts.)
8.
Depress the CAPACITOR LEAKAGE button and
read the leakage current. A good high voltage diode
will typically show less than 2 uA of reverse current.
HIGH POTENTIAL TESTING
The LC103 ReZolver can be used to locate leakage
currents as low as 0.1 uA, such as the leakage between
PC board foils, leakage between windings of a
transformer, and leakage between switch contacts and
shafts. These leakage currents are much too small to be
measured with an ohmmeter, but are measurable when a
high voltage potential (Hi-Pot) is applied with the
LC103 leakage power supply.
———————— WARNING —————————
This test is only to be performed by a person who
understands the shock hazard of up to 1000 volts
applied to the component under test when the
CAPACITOR LEAKAGE TEST button is depressed.
DO NOT hold the test leads or the component under
test in your hands when making any Hi Pot test.
————————
ATTENTION
————————
Le LC103 est fait pour être utilisé par une personne
qui est techniquement capable et qui comprend les
chocs que peut produire l’équipement (jusqu’à 1000
V) lorsque le test de fuite est utilisé. NE PAS tenir la
capacité dans la main ou toucher la conde ou la
patter de la capacité pendant le test de fuite.
Traces on a bare printed circuit board should show no
leakage when tested at 1000 volts with the LC103. Any
leakage indicates contamination on the board, or fine,
hair-like projections from the etched traces shorting
between the traces.
