Leakage: Diode. --To test the reverse leakage
METER Mode. --Before testing a transistor
of diodes, install the diode in the diode socket.
in any of the METER modes, you should test the
You now determine whether the diode is good by
transistor in one of the visual modes. This will
testing the device in the visual mode. Once you
tell you whether the transistor is an NPN or a
determine that the diode is good, place the
PNP. After determining this, put the POLARITY
POLARITY switch to NPN. Turn the FUNC-
switch in the proper position to agree with the
mode, and set the
TION switch to the
indication in the visual mode.
RANGE switch to 100 mA. Now check to see that
the meter is at zero, as mentioned before. After
Beta. --To test the Beta of the transistor, set
zeroing the meter, set the RANGE switch on the
the FUNCTION switch to the BETA position.
lowest range possible that still permits less than
Next, set the RANGE switch to the appropriate
full-scale deflection on the meter. Read the
position according to the power capability of the
leakage on this range.
transistor under test. After the RANGE switch
is in the proper position, operate the push-button
Material Identity: Diode. --To test the material
switch marked ZERO. Now adjust the ADJ knob
identity of a diode with the diode properly
for a zero reading on the meter. Next, actuate the
installed in the socket. Place the POLARITY
push-button switch marked BETA and adjust the
switch in the PNP position (zero the meter) and
CAL knob for full-scale deflection. Release the
the FUNCTION switch in the IDENT position.
BETA push-button switch; now the Beta of the
Using the leads, short the base and collector
device will show on the meter. Take care in
terminals together. The meter will show either
selecting the Beta range to test the transistor. It
germanium or silicon, as described before in the
is possible to damage small signal transistors
IDENT mode for transistors.
should you try to test them in the 2 mA Ib (LG.
PWR. XSTR) mode.
--To test a transistor for
set the FUNCTION switch on the
proper position. Next, set the RANGE switch to
Do not identity test transistor material with
the base and collector leads shorted
the 100 mA position. Then push the switch
together. This may create an erroneous
marked ZERO and adjust the ADJ knob for a
zero reading on the meter. Now release the ZERO
button. Set the RANGE switch on the lowest
Model 109 Probe
leakage range, which will still permit less than full-
scale deflection on the meter. You may now read
The Model 109 probe, used with the Model
the leakage directly off the meter. Read the
900 tester, is easy to use, having one-hand
first and then . Use this order because the
operation. It automatically adjusts to any spacing
meter will read down scale when switching from
between one-thirty second inch to five-eighths
Also, you can increase the meter
inch. You can rotate each probe point in a full
sensitivity. However, if you read
360-degree circle. The points are individually
then switch to
the meterill read up scale.
spring loaded for proper contact. You can
It is now possible to peg the meter. Although the
connect the probe to three printed circuit board
meter has protection, avoid undue abuse.
terminations. The probe has the extremely low
Material Identity: Transistor. --To use this
of the probe eliminates unsoldering while making
instrument in the IDENTITY mode, set the
in-circuit tests of transistors, diodes, ICS, and
FUNCTION switch to IDENT. Check the ZERO
other components. Finally, the retractable cord
ADJUST on the meter as mentioned before. After
stretches to a full 12 feet.
setting the ZERO, release the ZERO pushbutton.
Now note whether the needle reads above or
DESCRIPTION. --The Model 109 three-point
below the mark on the meter face just short of
probe speeds servicing of printed circuit
half scale. If the meter reads below the mark, the
assemblies that have transistors, diodes, and most
device is a germanium transistor. If it reads above
other board mounted components. You can make
the mark, it is a silicon transistor. This
instant connections to three points on a printed
information can be extremely useful when trying
circuit board. You will make rapid evaluation of
to substitute transistors.