Checks and corrective measures
No sound in right
a. Defective earphone.....................
a. Remove and replace right earphone
b. Loose connection at right
b. Tighten loose earphone setscrews.
c. Loose solder connections in
. Check solder connections and re-
left dome assembly.
d. Defective overhead cord
No audio signal
a. Defective microphone .................
a. Remove and replace microphone.
b. Loose connections at microphone
b. Tighten loose microphone
or in left dome assembly.
c. Defective microphone extension
d. Defective microphone jack
e. Defective solder connections
e. Check and resolder connections in
in left dome assembly.
left dome assembly. Replace
microphone cords as necessary.
Distorted or garbled
Cracked, bent, or broken diaphragm
Distorted or garbled
to be fault of
should again be heard and the ohmmeter should
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
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
plug. A sharp, loud, audible click should be heard and
The same test can be performed with the microphone
element removed from the headset-microphone by
touching the multimeter leads to the terminals on the
b. The earphone assembly and associated
Removal and Replacement of Microphone
wiring can be checked in a similar way. With the
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