Item
No.
Trouble symptom
Probable trouble
Checks and corrective measures
4
No sound in right
a. Defective earphone.....................
a. Remove and replace right earphone
earphone.
b. Loose connection at right
b. Tighten loose earphone setscrews.
earphone.
c. Loose solder connections in
left dome assembly.
solder if necessary.
d. Defective overhead cord
overhead cord.
5
No audio signal
a. Defective microphone .................
a. Remove and replace microphone.
transmitted from
b. Loose connections at microphone
b. Tighten loose microphone
microphone.
or in left dome assembly.
setscrews.
c. Defective microphone extension
cord.
extension cord.
d. Defective microphone jack
cord.
e. Defective solder connections
e. Check and resolder connections in
in left dome assembly.
left dome assembly. Replace
microphone cords as necessary.
6
Distorted or garbled
Cracked, bent, or broken diaphragm
Replace earphone.
reception.
in earphone.
7
Distorted or garbled
Defective microphone......................
Replace microphone.
transmission
(determined not
to be fault of
associated
equipment).
should again be heard and the ohmmeter should
2-8.
Equipment Checks
indicate a resistance of 20 ohms.
The electrical characteristics of the 19LB-87 can be
c. Ohmmeter checks at the telephone plug
checked with Multimeter TS-352B/U.
should yield the following results:
a. The microphone element and associated
wiring may be checked using the X1 ohmmeter function
Contacts
Resistance (ohms)
of the multimeter.
With the microphone element
positioned near the ear, touch the multimeter leads to
∞
the first and third terminals of the U-93A/U telephone
1-2
plug. A sharp, loud, audible click should be heard and
1-3
3.5
the ohmmeter should indicate a resistance of 3.5 ohms.
∞
1-4
The same test can be performed with the microphone
∞
2-3
element removed from the headset-microphone by
2-4
10
touching the multimeter leads to the terminals on the
∞
3-4
microphone element.
b. The earphone assembly and associated
2-9.
Removal and Replacement of Microphone
wiring can be checked in a similar way. With the
Element
headset properly positioned on the head, and the
a. Remove the two fastening screws from the
multimeter set on the X1 ohmmeter function, touch the
base of the microphone element.
meter leads to the second and fourth terminals of the U-
b. Disconnect the microphone extension cord
93A/U telephone plug. A sharp, loud, audible click
from the microphone element.
should be heard from each earphone and the ohmmeter
c. Remove the machine screw that secures
should indicate a resistance of 10 ohms. An individual
earphone can be checked in the same way after it has
been removed from its dome assembly. A sharp click
10
Previous Page
