Heathkit IT -3120 - Specifications

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The following procedure pertains to both in-circuit and
out-of-circuit testing. If you do not obtain the proper results
when the transistor is tested in-circu it, remove it from the
circuit and repeat the tests .
Beta (Gain) Test
1. Be sure the ON-OFF swit ch is in the OF F (out)
position.
2.
Identify each lead of the transistor.
3.
Connect the base (b) lead of the transistor to the B
connector (white) on the Tester.
4.
Connect the emitter (e) lead of the transistor to the E
connector (red) on the Tester.
5.
Connect the collector (c) lead of the transistor to the
C connector (black) on the Tester.
6. Press the TRANS switch.
7. Press the B ETA = 00 switch.
8. Determine the transistor class (signal, intermediate
power or power). Then p ress the approp ria te range
switch
to select the proper cu rrent.
9.
Identify the transistor type (N PN or PNP ). Then place
the NPN-PNP switch in the appropriate position. If the
type is not known, assume it to be an NPN device.
10. Press
the ON-OFF switch to the ON (in) position.
11. Adjust the SET B ETA = 00 control to place the meter
pointer over the 00 mark on the beta scale. If you are
unable to adjust the meter pointer or if it deflec ts o ff
scale, the transi stor may be defective or incorrectly
connected to the Tester.
12. Make sure the BETA CAL control is pu shed in and
turned fully counterclockwise.
13. Press the BETA CAL switch.
14. Rotate the BE TA CAL control and noti ce that the
meter pointer moves accordingly. If the pointer does
not move or defl ects off scale, the transistor may be
defective, incorrectly connected to the Tester, or the
NPN-PI\lP switch may be in the wrong positi on .
15. Adjust the BETA CAL control to place the meter
pointer over the desired calibration mark (CAL Xl0,
CAL X5, or CAL Xl) on the beta scale. Asa rule, use
the CAL XlO mark. Lo wer settings reduce the
collector current accordingly as shown in Figure 4 .
NOTE:
If you cannot position the meter pointer at
the desired calibration mark when testing power
transistors, pull out on the BETA CAL control to
extend its range. If you are still unable to calibrate the
Tester at the desired mark, especially when the
transistor being tested is in-circuit, use the next lower
calibration mark (CAL X5 or CAL Xl).
16. Press the BETA switch. Note the meter indication.
Multiply this indication by the calibrati on setting
(CAL Xl0, CAL X5, or CAL Xl) to obtain the actual
transistor beta. NOTE: If the meter indication is
greater than 50, a lower current range may be selected
to provide an additional multiplication factor of 10 as
explained previously (only on ranges 10 mA or
higher) .
A
transistor that is tested in-circuit and that has a beta
of less than 10 sh ould be removed from the circuit and
retested . As a rule, any transistor that has a gain less
than 10 when tested au t-of-circu it should be
considered defective.
The previous steps have explained the beta testing
procedure. If the device is out of the circuit, the following
leakage
tests w ill further test the transistor .. Disregard the
next two steps if you are going to perform the leakage tests.
17. R
elease t he ON-OFF switch to the OFF (out)
position.
18. Disconnec t th e transistor from the Tester.
T ra nsistor Leakage Tests
Leakage tests must always be performed with the transistor
out of the circu it, since the resistance of the circuit could
cause erroneous readings.
Three leakage measurements (lebo, Ices, and leeo) will be
made in the following steps.
lcbo is the measurement of the leakage current (l) between
the collector (c) and the base (b) with the emitter open (0).
This measurement should always be the lowest of the
leakage measu rements.
Ices is the measurement of the leakage current (1) between
the collector (c) and the em itter (e) with the base shorted (s)
to the emitter.
leeo is the measurement of the leakage current (I) between
the collector (c) and the emitter (e) with the base open (0) .
This measurement should always be the highest of the three
leakage measu rements.