Valcom vmt-1 Service Manual
VMT-1
INPUT MATCHING TRANSFORMER
CONNECTIONS
The VMT-1 matches 500-600 Ohm lines to either
a high impedance input or output of an amplifier.
It may be used to connect audio page ports of
telephone systems to most 70 Volt amplifiers.
The VMT-1 provides an impedance match
between a 500-600 Ohm balanced line and
auxiliary high impedance input or 25 Volt output
of an amplifier.
HI Z Out
HI Z Out
SHLD
Figure 1
Connection to an auxiliary input of an amplifier is
made using a standard phono patch cable or
screw terminals. Connection to a 500-600 Ohm
input is made to screw terminals. A shorting
jumper is available when the unit is used to
connect a high impedance output to the
microphone input of an amplifier.
DIMENSIONS/WEIGHT
• 1.75" H x 3.75" W x 1.25" D
(4.45cm H x 9.53cm W x 3.2cm D)
• 0.5 lbs. (.23 kg)
600-OHM
Input
CT
Shorting
Jumper
M
I
C
N
O
R
M
Shield
Plug
Shorting
Jumper in
Normal
Position
To Au x. Input
of Amplifier
Figure 2 shows the VMT-1 used to
connect a 600 Ohm balanced line to the auxiliary
input of a commercial 70 Volt amplifier. If the
amplifier uses phone jacks for auxiliary input
connections a patch cable with male phono ends
may be used for the connection. Shielded single
conductor wiring is used when the amplifier is
equipped with screw terminal connections.
HI Z Out
HI Z Out
SHLD CT
600-OHM
Input
Phono
Plug
OR
600-OHM Balanced
Line Input
Phono
Figure 2 Input Matching Ttransformer
To connect a 600 Ohm line to a ¼
microphone input of an amplifier move the
shorting jumper to the lower 2 header pins on the
unit. The connection the amplifier may be made
using a standard patch cable with phono plugs
and a ¼” male/phono jack adapter.
Issue 0
1 947993
Shorting
Jumper
M
I
C
Sh ield
Phono
Plug
N
O
R
M
In M ic.
Position
To M ic. In pu t
of Amplifier
Female Phono to ¼” M ale
Switchcraft 343 or Equiv.
Phono
Plug
HI Z Out
HI Z Out
SHLD
OR
600-OHM B alanced
600-OHM
Input
CT
Line Input
FIGURE 3: Connection to Microphone Input
Connect 25V speaker line common to HIZ
Shld. screw terminal. Connect other side of 25V line
to the remaining HIZ out screw terminal. Connect
500/600 balanced line to VMT-1 screw terminals
Designated 600 Ohm Input. Shorting jumper should
be in norm. position
HI Z Out
HI Z Out
SHLD
600-OHM
Input
CT
Shorting
Jumper
Norm.
Position
TECHNICAL ASSISTANCE
When trouble is reported, verify the unit is
properly connected and there are no broken
connections leading to this unit. Ascertain
volume control is turned up.
Assistance in troubleshooting is available from
the factory. When calling, you should have a
VOM, a test set and call from the job site. Call
(540) 563-2000 and press 1 for Technical
Support or visit our website at
http://www.valcom.com.
Valcom equipment is not field repairable.
Valcom, Inc. maintains service facilities in
Roanoke, VA. Should repairs be necessary,
attach a tag to the unit clearly stating company
name, address, phone number, 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
To 600 Ohm
To 25V Output
of Amplifier
Amplifier
Com.
25 V
Term.
Balanced
Input
FIGURE 4: Match 25V Speaker Line to
600/500 Ohm Input
Valcom, Inc. warrants its products to be free from defects in materials and workmanship under conditions of normal use and service for a period of one
year from the date of shipment. The obligation under this warranty shall be limited to the replacement, repair or refund of any such defective device
within the warranty period, provided that:
1. inspection by Valcom, Inc. indicates the validity of the claim;
2. the defect is not the result of damage, misuse, or negligence after the original shipment;
3. the product has not been altered in any way or repaired by others and that factory sealed units are unopened (a service charge plus parts
4. freight charges for the return of products to Valcom are prepaid;
5. all units ‘out of warranty’ are subject to a service charge. The service charge will cover minor repairs (major repairs will be subject to
This warranty is in lieu of and excludes all other warranties, expressed or implied and in no event shall Valcom, Inc. be liable for any
anticipated profits, consequential damages, loss of time or other losses incurred by the buyer in connection with the purchase, operation, or
use of the product.
This warranty specifically excludes damage incurred in shipment. In the event a product is received in damaged condition, the carrier should be notified
immediately. Claims for such damage should be filed with the carrier involved in accordance with the F.O.B. point.
Headquarters: In Canada
Valcom, Inc. CMX Corporation
5614 Hollins Road 35 Van Kirk Drive #11 and 12
Roanoke, VA 24019-5056 Brampton, Ontario L7A 1A5
Phone: (540) 563-2000 Phone: (905) 456-1072
FAX: (540) 362-9800 FAX: (905) 456-2269
and labor will be applied to units defaced or physically damaged);
additional charges for parts and labor).
VALCOM LIMITED WARRANTY
2 947933
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