TM 11-6625-539-l4-4
identification, refer to transistor base data in
c. Adjust the RANGE switch to X 10. Check for
meter zero. If necessary, zero the meter using the
section III of appendix D.
METER ZERO control.
f. Read transconductance on the GM scale. If
reading is less than 2500, set the RANGE switch
d. Adjust the RANGE switch as required by the
to X 1.0. Multiply scale reading by setting of the
value of the device under test as indicated in
RANGE switch.
section IV, appendix D. Set to:
X 0.1 for 0 to 10
g. Check the noted value against that listed in
X 1.0 for 0 to 100 A
section III, appendix D, for the device under test.
X 10 for0 to 1.0 mA
If the value is less than that indicated, reject the
device.
e. Insert the anode lead of the device into the C,
D connector of the transistor socket on the front
2-12. In-Circuit Testing of Field Effect Tran-
panel and insert the cathode into the E, S connec-
tor. If test leads are used, connect the red test
sistors (FET's)
lead to the anode and the yellow lead to the
In-circuit testing of FET's is identical to that for
cathode.
out-of-circuit testing described in paragraph 2-11,
f. Read leakage on the meter ICES , ICO , IR scale
except that after step e it is necessary to perform
and multiply the scale reading by the setting of
the following additional steps:
the RANGE switch. Reject the diode if leakage
a. Operate the FUNCTION switch to OHMS.
exceeds the value given in section IV of appendix
b. Operate the RANGE switch to X 1.0.
2-14. In-Circuit Testing of Diodes
c. Operate the POLARITY switch to EB posi-
tion.
You can perform in-circuit checking of diodes by
two methods, provided reverse leakage data for
d. Adjust ICES ZERO/OHMS ADJ COARSE and
fine controls to indicate infinite reading on OHMS
If an "a" appears in the column, only the qualita-
scale of meter. Short together the E-B jacks. Zero
tive diode in-circuit check can be made. If a value
the meter using the METER ZERO control. Re-
is available, you can also make a reserve leakage
move the short and readjust as necessary for an
measurement.
infinite reading. Repeat the procedure as required
until zero and infinity are properly set.
a. Diode In-Circuit Check.
(1) Operate the FUNCTION switch to DIODE
e. Check parellel G-S circuit resistance on the
meter using the red OHMS scale. It shall be 100
IN/CKT position.
ohms minimum. Operate the POLARITY switch
(2) Operate the POLARITY switch to PNP
to E-C and check parallel S-D circuit. It shall be
position.
4K ohms minimum. If these requirements are
(3) Operate the RANGE switch to X 1.0 posi-
met, the in-circuit transconductance readings as
tion.
indicated in paragraph 211f and g are reliable.
(4) Connect the red test lead to the anode of
the device under test and connect the yellow lead
to the cathode.
2-13. Out-of-Circuit Testing of Diodes
(5) Check the position of the meter pointer on
Before attempting to make the out-of-circuit re-
the DIODE IN/CKT scale of the meter. If it
verse leakage test described in this paragraph,
deflects to the GOOD range, the device is not open
you must check section IV of appendix D for the
or shorted. If it deflects not at all or only into the
device to be tested to determine if a reverse
BAD range, the device is open or shorted and
leakage value has been assigned. If none has been
should be rejected.
assigned, the IR column lists an "a" for the device.
NOTE
In this case, you cannot perform a reverse leakage
test. If a reverse leakage value is listed in the IR
During in-circuit diode testing, if there is
column, proceed with the out-of-circuit test as
litter or no parallel resistance in the
follows:
circuit, the meter pointer may deflect
fully up scale, striking the peg. This is
a. Set the FUNCTION switch to ICO, IR.
normal operation, indicating that the
b. Set the POLARITY switch to PNP.
diode is not open or shorted.
2-6
