Channel Vision Digital RF Modulator E-1200 - Manual (Page 5)

3 Check all connectors for 75
Ω
.
Noise on the Audio
1.
Insert grounding block in line and ground coax cable
before it enters the TV.
2. Use professional grade audio/video interconnect between
the components and the modulator.
Audio is Too Low
Use a Y-Connector to combine the left and
right audio before entering the modulator.
Herringbone in Picture on Modulated Channel
Disconnect modulator from local channels
an check modulated channel.
A) If there is programming move the
modulated channel.
B) If the picture is snowy, use a #3102-80 low pass filter
to
block noise or data coming in from cable company.
C) Separate modulated channels by two channels.
Horizontal Bars Rolling Through TV Picture
1.
Check for a component of the system to introduce DC
power into the system. Disconnect that component and
check TV. If the hum bars stop, use a DC blocker down
stream from that component to block the power from
getting to the TVs.
2. If the rolling is only on the modulated channels, check for
impedance mismatch by adjusting the video level
adjustment pot.
Vertical Bars Rolling Through TV Picture
Check for AC power getting on the line. Use a ground
breaker in line.
Black and White Lines on one Local Channel
Move modulated channel up to a new channel. If problem
persists and all of the inputs of a multiple input modulator
are not being used, check default channels on modulator
to see if default channel is set to the same channel that the
problem channel is set to.
Flashing at the Top or Middle of TV Picture
1.
If flashing is on modulated channels, turn up attenuator/
down gain of modulator.
2. If flashing is on local channels, attenuate output of
amplifier.
3. Remove cable TV from system. If flash stops, install
filter #3102-__ to fix problem.
Picture is Tearing
Possible impedance problem. Check that impedance
switch is set to 75
Ω.
Ghosts on the Picture
1.
Terminate all unused ports with 75
Ω
terminator model
2101.
2. Check for low quality combiner in system. Replace with
high isolation combiner, HS model combiner.
leakage may occur or if the shielding braid is touching the
center conductor.
2. Install model CVT-15PIA amplifier after the combiner.
Grainy Modulated Channel : Good Picture on the Cable
Channels
1.
Disconnect cable channels from the system and check the
modulated channels.
A) If the modulated channels are good, use a low pass filter to
"clean-up" the incoming frequencies to be modulated.
B) If the modulated channel does not improve after
disconnecting the local channels, evaluate signal loss of
modulator through the splitters and cable length of the
system. Amplify after the combiner if needed.
C) Also check the connections between modulator and the
combiner for leakage or the cable braid is touching the
center conductor.
2. Make sure the attenuator adjustment on the back of the
modulator is turned to maximum output power.
3. Check output strength with field strength meter.
4. Connect modulator directly to TV and check picture quality.
5. Check bandwidth of all splitters and amplifiers for 1GHz
capability.
6. Place TV cable setting on standard, NOT HRC or IRC.
TV Won't Tune High Enough to get Modulated Channel
1.
Use an external tuner i.e. VCR or a Cable Box converter tuner
to allow the TV to view a modulated channel on a channel
through the external tuner.
2. If the modulated channel is beyond the capabilities for that TV,
the TV will not work with the system.
Cable Company Box Won't Pass a Modulated Signal
1.
Connect modulator directly to TV and verify the
modulator is sending a signal the TV can receive.
2. Use model 3101 Cable Box Combiner Kit to route
the modulated signal around the cable box. See
schematic page.
Cable Company Uses All Available Channels
1.
Use a low pass filter (3102) to block out channels 80 and above
for clean modulation (won't effect channels 95-99).
2. Call for pricing on a custom filter to block out a specific channel
or multiple channels.
Modulated Picture is Too Bright or Washed Out
1.
Adjust the white video level. Adjust port on the
chassis located under the white cover plate above the channel
select to the proper brightness.
2. If using a camera, check positioning of the lens to be sure it's not
aimed at the sun or a reflection.
3. Adjust camera lens - see lens manual.
Modulated Picture is Too Dark
1.
If baseband video is being split with a Stereo
Loop Kit or loop through quad, set impedance
matching switch or potentiometer
(termination switch) to 1
ΚΩ.
2. Adjust the white video level adjust pot on the
chassis located under the white cover plate
above the channel select to the proper
brightness.
O u c h!!!