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c.
(contd)
+
SIt
SCR
+_-.....
RES
..... J.o" .......
~o--
.....
I
6 VOLT...J::
"'---IO-A-
MULTIMETER
BATTERY-
2W
The multimeter is selected to read ohms on the lK
scale, and is connected to read the forward resistance
of the SCR.
When switch SW is closed, the forward re-
distance of a good
SCR will change from a high value
(lOOK to infinity) to a low value (1 to 10K).
When
the switch is opened, a good
SCR will revert to its
high forward resistance or blocking state.
A faulty
sea
will not switch, remaining in either an open or
a conducting state.
d.
If any
SCR's are suspected of being faulty from the
above resistance checks, the
SCR conversion module
should be removed from the case.
After the
sca
pig-
tail (cathode) and gate leads have been disconnected"
recheck the forward and reverse resistances before
replacing the
SeR heatsink assembly.
This should be
done before an
SeR is definitely classified as damagec
or faulty, since a fault in another
SCR or another
part of the circuitry can produce a faulty reading
from a good
seR
before it is disconnected from the
circuit.
6-~
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