3
VH250P). Check Brightness and Contrast controls on
front of monitor. If screen IS LIGHTING UP but there
is no picture, you probably are not getting a video signal
from the camera to the monitor. Starting at camera,
check for video signal through coax cable, and through
(VDU-4) video distributors (if used). Check for approx.
12VDC power at each VDU-4 video distributor (if
used). Check coax connector at camera(s) to make sure
it is not shorted or open. Temporarily switch monitor PC
board (VH250E or VH250P) with one from a function-
ing location.
4. NO VOICE ON SYSTEM: Check volume control
potentiometer on NH200A amplifier. Check terminals
'T', 'O', and 'M' to handsets. Check speaker/microphone
connections at each entry station. Disconnect terminals
'T', 'O' and 'M' to system amplifier, and connect a single
handset to those terminals. If voice is working, amplifier
and entry speaker/microphone are O.K., so check riser
wiring. If not amplifier or speaker/microphone could be
faulty. Check by replacement.
5. UNABLE TO RELEASE DOOR STRIKE: Check
wiring to handset terminals '1' and 'O'. Temporarily
remove door opener wire from terminal '1' and touch to
terminal 'O'. Check operating voltage of door opener
matches output from system amplifier. Check wiring
(and gauge) to door opener, from amplifier/power sup-
ply. When using a magnetic type lock or other 'fail-safe'
type door lock, you should use a reversing relay, such as
our model# PK407A for each entrance.
6. HUM OR BUZZ: Check system wiring installed too
close to power wiring or electrical devices or transform-
ers; check transformer(s) installed too close to control
equipment (should be at least three (3) feet away).
Wiring is being run next to wiring for other systems and/
or devices.
7. MONITORS TIMING OUT TOO QUICKLY:
Check adjusting control potentiometer on VH250E (or
VH250P) PC board and adjust as needed from approx.
0 to 180 seconds. Calibration is not exact, so please
check timing after re-adjusting.
8. MONITORS DO NOT TIME OUT AT ALL:
Check for shorts and/or grounds on system. Tempo-
rarily switch monitor with one from a functioning loca-
tion. Check that entry station pushbutton is not stuck or
shorted. Temporarily switch monitor PC board (VH250E
or VH250P) with one from a functioning location.
PLEASE NOTE: If these checkpoints fail to indicate the
problem, there may be an equipment or wiring fault. Please
contact the factory or a qualified service representative
VMH25 COMPONENT LISTING
TYPICAL REPLACEMENT PARTS
Model# NH200A: Intercom amplifier unit. One (1) re-
quired for system for call, intercom and door release
functions. Requires SS106 transformer for power.
Model# VRU: Video Monitor Power Supply unit. One (1)
required for each four (4) (or less) monitors. Requires
SS146 transformer for power.
Model# VDU-4: Four (4) output Video Distributor. One
(1) required for each four (4) (or less) video outputs to
monitor risers/lines.
Model# TU1007A: Multiple Entrance audio switching
adaptor. Used to switch the voice (and door release) to
the calling entrance. One (1) required for 2 entrances,
two (2) required for 3-4 entrances, three (3) required for
5-6 entrances, and four (4) required for 7-8 entrances.
Used on systems with more than one (1) entrance
station.
Model# DPS-2 (TUV2): Multiple Entrance video switch-
ing adaptor. Used (in addition to the TU1007A) to switch
the video to the calling entrance. One (1) required for 2
entrances, two (2) required for 3-4 entrances, three (3)
required for 5-6 entrances, and four (4) required for 7-
8 entrances. Used on systems with more than one (1)
entrance station, where video switching is required.
Not
Used*
Not
Used*
Monitor
'ON'
Button
* These buttons and cap blanks are used on other systems
and do not apply to this configuration
ON
