of the curve tracer front panel. Either set of jacks
may be used. The SOCKET switch activates only
the left or right set of jacks at a given time, along
with the respective plug-in socket.
The external transistor jacks, FPS probe lips and
plugs have been color-coded for easy identification:
COLOR
TRANSISTOR
FET
blue .......... collector ........... drain
green ........ base .............. gate
yellow ....... emitter ............ source
After a short period of usage, the color-code
scheme becomes so automatic that no time is re
quired for lead identification.
In-Circuit Probe
Most transistors in consumer and industrial equip
ment are mounted on printed circuit boards with the
collector, base and emitter quite closely spaced.
Measurements in such circuits are normally made
from the side opposite the components. The B & K
Model FP-5 Probe, supplied with the curve tracer, is
ideal for in-circuit testing of semiconductors in such
circuits. The probe has three tips which permit
contact with the collector, base and emitter (or drain,
gate and source of FET) simultaneously and each
one pivots to allow for different spacing. Since all
three connections can be made using only one hand
to manipulate the probe, troubleshooting is acceler
ated.
COMPLETELY REMOVE POWER FROM
EQUIPMENT UNDER TEST. THE CURVE
TRACER SUPPLIES THE COMPLETE TEST
SIGNAL. ANY ADDITIONAL SIGNAL OR
DC CURRENT MAY INVALIDATE THE
TEST RESULTS AND COULD RESULT IN
DAMAGE TO THE EQUIPMENT.
To use the probe, connect the plugs of the probe
cable to the C-D, B-G and E-S jacks of the curve
tracer. Connect the yellow, blue and green plugs
to the correspondingly colored jacks. Either the left
or right set of jacks may be used; the SOCKET
switch selects the set that is activated at a given
time. The emitter and collector tips of the probe are
slightly longer than the base tip. Normally the emit
ter and collector connection is made first by holding
the probe perpendicular to the circuit board, then
tilting the probe until the base tip makes connection.
Identify the base, collector and emitter of the semi
conductor from the manufacturer's diagrams of the
equipment under test.
Diodes
Connections to diodes are made using only the
collector-emitter terminals. Polarity is not of par
tic1llar importance since it is easily reversed with
the POLARITY switch. However, if the cathode of
the diode is always connected to the emitter termi
nal, the POLARITY switch is set to PNP for reverse
bias and to NPN for forward bias. Reverse bias is
applied for testing zener diodes, leakage of signal
and rectifier diodes and inverse peak breakdown
voltage. Forward bias characteristics show voltage
drop across the diode junction and resistive or open
conditions.
TYPICAL SEMICONDUCTOR TESTS
F coniliarization with the Curve Tracer
To become familiar with using the curve tracer,
it is suggested that you gather an assortment of
good semiconductor devices and test them one by
one, observing the normal results, effects of read
justing the controls, peculiarities of various semi
conductors, etc. More specific information on anal
yzing the displays to accurately measure gain (beta),
voltage breakdown, etc., is given later in this man
ual. At this point, more emphasis should be placed
on recognizing normal and abnormal displ
ay
s and
how to set the curve tracer controls to obtain a
normal display.
The user should become familiar with the normal
results obtained by testing semi-conductors out of
circuit before starting to use the curve tracer for
in-circuit testing.
Transistors and other semiconductor devices are
tested with respect to manufacturer's specification
sheets, which state certain conditions of the test and
minimum performance standards. It should be real
ized that it is normal for characteristics of some
devices to vary quite widely from one semiconductor
to another although they have the same type num
ber. However, manufacturer's specification sheets
are not always readily available. Additionally, the
manufacturer and type number are not always
easily determined. Nevertheless, the semiconductors
may be tested and determined to be good or bad.
In fact, the test will help identify or categorize the
semiconductor. Most transistor failures are of the
catastrophic type, wherein it will be shorted or open.
The curve tracer will immediately show such failure.
It will also immediately identify a good transistor
of unknown type as NPN or PNP. The normal oper
ating current range can be rapidly determined and,
with experience or reference data, the device can be
categorized.
Transistor Testing Procedure
A typical test of a transistor follows:
(refer to Figure 10):
1. Turn on the curve tracer and oscilloscope. Cali
brate the oscilloscope if not already calibrated.
2. Set the VERTICAL SENSITIVITY and STEP SE
LECTOR controls to the "fast set-up" markers
(•). Set the SWEEP VOLTAGE control to zero.
3. Plug the transistor into the left or right socket
on the curve tracer, or connect test leads from
the left or right C, B ,and E jacks to the collectar,
base and emitter of the transistor. Set the
SOCKET switch to select the socket or jacks in
use.
4. Set the POLARITY switch to NPN or PNP to
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