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"Dr" (Diode Reverse) Test Circuit (Figure 20)
In this test, a reverse DC voltage is applied to the diode. Meter polarity is opposite to
that of the "Df" test. Value of applied voltage is governed by the "A" switch setting. Value of
meter shunt depends on the "C" switch setting.
SILICON
BlK
.' Cathode
RECTIFIER
33K
100
3.21..0.
Rc
-. MFD
-. CRYSTAL
DIODE
"
YEL
FIGURE 20
FUNCTI ONS OF FRONT PANEL CONTROLS AND SWITCHES
1. "ADJUST LINE" control compensates for varying line voltage conditions.
2. Switch "A" is the collector voltage selector for lebo readings.
It
provides 17 predetermined
values of collector voltage from .5 volts DC to 100 volts DC. (See schematic for the com
plete list of collector voltages available through Switch "A".) Switch "A" also selects AC
voltages in the "Df" (Diode Forward Current) test.
3. Switch "B" is the base current injection selector (for gain tests) for all classes of transistors.
. Position
Injection
Type
1
50 Microamperes
Low Power
2
200 Microamperes
Medium Power and Misc.
3
500 Microamperes
Medium Power and Misc.
4
2 Milliamperes
Medium Power and Misc.
5
5 Milliamperes
Power
CRYSTAL
DIODE
470.0..
---1+
P
+
05
3.7VAC
O-GOJL
I
FIGURE 21
Switch
HB"
also varies the meter sensitivity for transistor leakage and gain tests ("L ",
''GX1'', and ''GX5'') and diode forward c'urrent test ("Df").
4. Switch "C" is the meter "lebo" and "Dr" sensitivity selector. This selector sets up
the indicating circuit for all "lebo" readings. The switch is discussed in greater detail
under "Operating Instructions - lebo test."
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