7
947939A
OPERATION
Circuit Description
The V-9939A Microphone Adaptor has inputs for
both high impedance and balanced low impedance
microphones. It also has an input for a push to talk
contact closure. When the closure is applied, a high
gain pre-amplifier is turned on and the output relay is
activated. The unit will stay active until the contact
closure is removed. The preamplifier circuit also
contains a voice limiting circuit to limit extremely
loud inputs.
TECHNICAL ASSISTANCE
When trouble is reported, verify that power is being
supplied to the unit and there are no broken
connections. Check voltages for proper polarity on
the crossconnect block.
Table 1 identifies symptoms of some possible
problems with solutions. If a spare unit is available,
continue to troubleshoot by substituting the spare unit
for the suspected defective unit.
Assistance in troubleshooting is available from the
factory. When calling, you should have a VOM and a
test set available and be calling from the job site.
Call (540) 427-3900 and ask for Technical Support,
or call (540) 427-6000 for Valcom 24-hour
Automated Support or visit our website at
http://www.valcom.com.
The V-9939A is not field repairable. Valcom
equipment contains no user serviceable parts
inside. Valcom, Inc. maintains service facilities in
Roanoke, VA. Should repairs be necessary, attach a
tag to the unit clearly stating your company name,
address, phone number, and contact person; and the
nature of the problem.
Send the unit to:
Valcom, Inc.
Repair and Return Dept.
5614 Hollins Road
Roanoke, VA 24019-5056
TABLE 1 - TROUBLESHOOTING CHART
SYMPTOM
1. No relay operation in V-9939A
when microphone talk button is
pressed.
2. Relay operation but no output.
3. Audio from V-9939A but not
from V-1094A.
4. No output from V-1101A.
5. Output from V-9939A and
V-1094A or V-1101A but not
from speakers.
SOLUTION
Check for –24 VDC at V-9939A across the PWR terminals. Verify
connection from microphone to terminals SW and GND OUT (refer to
the Installation section).
Verify connections from microphone to MC and HZ or LZ terminals.
Turn volume control up (clockwise).
Verify Tip and Ring connections from V-9939A to V-1094A. Verify
proper voltage and polarity at –24 VDC and GND terminals of
V-1094A. Turn up volume at V-1094A.
Recheck all connections per Figure 5. Make sure the V-1101A passes
the power test in Figure 5, step 17.
Verify proper voltage and polarity to speakers. Verify audio
connections to speakers. Verify speakers are Valcom one-way amplified
speaker assemblies.
