AC Voltmeter
Camera
Monitor
Bridge Tap
NV-213
A
NV-213
A
NVT TROUBLESHOOTING
If you are experiencing problems, attempt to simplify your setup. Test each cable
segment separately. For example, test the camera and monitor together without the
other equipment. Then add in the NVT transceivers, back-to-back. Test each segment
of a long cable-run independently. Attempt to isolate the problem.
Below are problems that may be encountered. If the suggestions below are not helpful,
or the recommendations are not effective, please call NVT’s customer support. NVT
customer support can be reached 8:00 AM to 5:30 PM PST at (800) 959-9870 or at
(+1) (650) 562-0600.
FAINT OR BLURRY PICTURE; LITTLE OR NO COLOR
Possible causes include:
1. Shielded twisted-pair cable. Verify that the wire is unshielded twisted-pair cable.
Multi-pair cable with an overall shield is OK.
2. Longer wire distance than expected. Be sure to include any coax cable that’s part of
this distance. Verify end-to-end connectivity with an ohm meter. Measure the distance
by disconnecting the transceivers, shorting the far end, reading the loop’s resistance
at the near end. See above for ohm vs. distance ratings. If necessary, replace
transceivers with correct models specified for this distance.
3. Incorrect distance equalization setting. Adjust the equalization controls) with a mini
screwdriver (NV-652R, NV-862R or the NV-1662R). If the transmitter is an NV-653T,
verify correct equalization switch setting.
4. Poor connection at a punch-block, splice, or coax cable. Re-check using the
method described in #2 above, or use a wire test set.
5. Short between conductors of the twisted-pair. Use an ohm meter to locate the short.
6. Transient protection devices employing metal-oxide varistors. Use carbon blocks,
gas-discharge tubes, or NVT transceivers w
i
th built-in protection.
7. Check the camera. Are the focus and iris set correctly? Verify with portable monitor.
EXTREMELY FAINT PICTURE
Only faint shadows of the original picture are visible. One of the twisted pair conductors
is open or the wires are shorted together. Check with an ohm meter.
OVER-SATURATED COLORS; HIGH CONTRAST GRAINY PICTURE; TOO BRIGHT,
TORN PICTURE
Adjust the distance equalization as necessary. Verify that the monitor has a 75
termination, not in “
loop-through
”.
WON'T SYNC; WIDE, WHITE JAGGED AREAS
Looks like a scrambled Cable TV signal. Check polarity.
WON'T SYNC; TORN PICTURE
1. Make sure that you are using unshielded twisted pair wire.
2. Check distance equalization settings.
3. For installations with passive
(non-amplified)
transceivers at both ends, check for
ground loops. This may be done with an AC Voltmeter, as shown below:
If the voltage is greater than 1/2 volt, use an amplified receiver, such as the NV-652R,
NV-862R, or NV-1662R.
Alternately, remove the ground at one end
(usually at the camera end)
. Be sure that
floating the camera conforms to local/regional and National Electrical Codes.
4. Check for crosstalk from a second video path. Disconnect all other video sources.
If the problem goes away, check for a split-pair or un-twisted wire.
FAINT STRIPES GLIDING UP OR DOWN THE SCREEN
These are caused by crosstalk from a second video path, or with ground-loops in
installations employing passive models at both ends.
1. To identify, disconnect all other video signals temporarily. If the interference goes
away, check the wire to make sure the signal is traveling through a twisted pair. Is
two-way video being sent more than 1,000 ft (300m) over Category 2 or 3 wire? If so,
the send and receive signals may need to go in separate jacketed cables, or upgrade
to Category 5 wire.
2. Next, check for ground loops. See #3 above.
NO POWER LIGHT ON THE NVT UNIT
Check the blue “power” LED on powered NVT units. If the light is not on, the receiver
is not getting power. Re-check the power source and connections.
If the green LED is on but the power LED is off, check that the power supply is floating.
Grounding one side of the power input may cause this condition.
NO GREEN LIGHT, NO VIDEO
The NV-652R, NV-862R or NV-1662R series receiver/hub is not detecting a video
signal. There is an open or shorted connection. Use a multimeter to locate the fault.
GHOSTS
Faint shadows of the original signal shifted to the right. This is caused by an
impedance mismatch along the wire. Verify that the monitor is terminated with 75 (not
in “loop-through”.) Check that all wire is unshielded twisted pair. The high-frequency
wire impedance should be 100. Check for bridge-taps (see below) either by inspecting
wiring closet connections, or, if available, using a “Time-Domain Reflectometer”
(T.D.R.), sometimes called a “cable tester”.
If the faint shadows are not copies of the original picture, but from the picture of some
other camera, check for crosstalk:
Is any portion of the wire un-twisted?
Are the signals from two cameras split between two pairs?
Is there a short between a conductor of one signal and a conductor of another?
