TM 11-6625-539-14-4
circuit function
Figure No.
functions fail to operate, check for defective power
Regulated power supply
supply circuits or a defective meter circuit, because
Beta function circuit
all functions require the operation of these
Ohms function circuit
circuits.
FET test circuit
b. If partial operation of the unit is possible, run
ICES function test circuit
through a complete checkout of all functions to
ICO IR function test circuit
determine which are faulty. When faulty functions
have been isolated, a check of simplified schematic
d. If the square-wave output is questionable, use
diagrams will indicate common components that
an oscilloscope to check the waveform at the base
are used in the defective circuits, thereby helping
of transistor Q1 or Q2. The square wave must have
to isolate the fault.
approximately 2.5-volt amplitude peak to peak in
c. Following is a list of circuit diagrams related to
the beta function.
the various functions of the test set. Relate these
e. Faulty operation of the test set may be caused
circuits to the major schematic diagram given in
by improper calibration. If the unit gives consis-
tently incorrect readings in one or more functions,
the test set.
calibrate the test set as directed in paragraph 7-8.
Section IV. GENERAL SUPPORT MAINTENANCE OF TEST SET
I
7-8. Adjustustments
a. General. Adjustment of the test set requires
R6 (8, fig. 7-1) to provide a multimeter indication
of 1 mA. Remove the NPN transistor.
that you adjust five variable resistors mounted
(3) Set POLARITY switch to PNP. Connect a
on the back of the test set printed circuit board.
multimeter adjusted to read milliamperes and a
Remove the front panel from the case (para 7-9 to
good PNP transistor to the transistor test set as
provide access to the variable resistors. Main-
shown in figure 7-2. Adjust variable resistor R3
tain the connection between the battery power
(7, fig. 7-2) to provide a multimeter reading of 1
supply and the connector pins on the printed
mA.
circuit board, because the test set must be
(4) This completes beta adjustment. Remove
energized during the adjustment procedure.
the transistor and the multimeter from the test
Refer to table 7-1 for the required tools and
set.
equipment.
d. Offset Adjustment.
b. Battery Check. With the POLARITY switch
(1) Set FUNCTION switch to BETA position,
in the OFF position, operate and hold BAT CHK
the POLARITY switch to PNP, and the RANGE
switch in the direction of the arrow. Check to see
switch to X 0.1.
that the meter pointer deflects into the BAT
(2) Connect a good PNP transistor directly
CHK range on the scale (red).
into the transistor socket on the panel of the test
c. Beta Adjustments.
set. Connect a multimeter adjusted to read
(1) Set the FUNCTION SWITCH to BETA.
millivolts into the remote test jacks C, D and E, S.
Set the POLARITY switch to NPN. Set the
(3) Adjust variable resistor R8 (9, fig. 7-1) to
RANGE switch to X 0.1.
obtain a zero voltage indication on the multime-
(2) Connect a multimeter adjusted to read
ter (if analog) or 0.0 (if digital).
milliamperes and a good NPN transistor test set
as shown in figure 7-2. Adjust variable resistor
Change 1
