CM-7777v3 and CM-7778v3
The detailed troubleshooting instructions below are very comprehensive so as to try to eliminate any questions, in each step. You might consider making this initial quick test first, to confirm that the preamp, power supply and power inserter are ok. This could save you much time and you will not have to wonder if the problem is with the preamp system, or, with your antenna system installation. You'll know that you need to troubleshoot your antenna system to find the issue.
- If you are testing a CM-7778v3, you should get most all of the same channels that you can get without any preamp connected.
- If you are testing a CM-7777v3, then you may not get all of the same channels that you can get without any preamp connected. The CM-7777v3 is so strong that it can overdrive the input to your TV tuner. The symptoms are virtually the same as weak signals.
CM-7777v3 and CM-7778v3 Troubleshooting
- Verify all coax connections are correct as described below, and tightened. Note: Torque spec is 35 in-lbs NOT 35 ft-lbs. Just a little tighter than finger tight. Over-tightening will damage the printed circuit board and render the preamp useless. Use the included rubber boots to cover the connectors on the preamp for additional weather proofing.
- Connect a short coax cable from the antenna output, or the matching transformer that is connected to the 2 connection posts on the antenna. To the INPUT port on the CM-7777v3/CM-7778v3 preamplifier. Shorter is better than longer cable. The longer your cable, the more signal loss you will experience.
- The OUTPUT/POWER port on the CM-7777v3/CM-7778v3 preamplifier should be connected to the long coaxial cable that goes into the house.
- The other end of the long coaxial cable from the preamplifier OUTPUT/POWER port, connects to the TO AMP port on the power inserter.
- The TO TV port on the power inserter will be connected with a coax cable to the TV, splitter, or distribution amp.
- The power supply adapter that plugs into the wall power outlet will have a coax cable connected to it, that cable is in turn connected to the DC IN port on the power inserter.
- If all connections are correct and tightened, and you get no channels you can use a volt meter to verify the voltage, then check the following.
- When measuring voltage, touch your red/+ probe to the center conductor and touch your black/- probe to the metal body/ground of the coax connector.
- The voltage should be approximately 13.5VDC if your power supply is the 12VDC version adaptor. There is a small green power indicator on this power supply.
- The voltage should read approximately 21VDC if you have the 15VDC version supply.
- The voltage spec is on the label of the power supply adaptor.
- Connect a short coax cable to the wall power adaptor and measure the voltage at the end of that cable.
- If you do not measure DC voltage, then either the cable or the power supply adaptor is bad(If ok, continue).
- Reconnect the cable from the power supply adaptor, to the DC IN port on the power inserter.
- Connect a short coax cable to the TO AMP port on the power inserter and measure the voltage at the other end of the short coax cable.
- You should measure the same voltage at the end of the short cable as you measured on step #2 b & c above.
- Reconnect the long coax cable, that runs from your house to the location of the antenna and preamp, connect that long cable to the TO AMP port of the power inserter.
- Now, back up to the location of the antenna and preamplifier.
- Disconnect the coax cable from the preamplifier OUTPUT/POWER port and measure the voltage at the end of the long coax cable.
- You should measure the same DC voltage that you measured in step 2 above.
- If you do not measure any DC voltage at the end of that cable, then the cable is bad or interrupted.
- NOTE: You will not measure any DC voltage at the TO TV port of the power inserter
- NOTE: You will not measure any voltage on either port of the CM-7777v3 or CM-7778v3 preamplifier
- If proper voltage is measured at the 3 locations described above, then you have the basic system wired correctly.
- If you still get no signals
- Remove the cable that is connected to the DC IN port on the power inserter.
- Leave the power inserter in the system.
- The power inserter TO AMP port should remain connected to the long coax cable going up to and connected to your roof antenna.
- NOTE: You cannot have a standard splitter in the long coax cable run from the power inserter TO AMP port and the cable that connects to the preamp OUTPUT/POWER port. The standard splitter will block the voltage from getting to the preamplifier.
- You can use DC/power passing splitters. You can find them here.
- The coax cable that is connected to the TO TV port of the power inserter should be remain connected directly to a TV.
- Remove the preamplifier and connect the long coax cable directly to your roof Antenna or its matching transformer/balun.
- Remove the cable that is connected to the DC IN port on the power inserter.
- In most instances, your stronger signals will be present and detected by your TV.
- If you live in a location with very weak signals, or the cable that runs down from the antenna to your house is very long, you might not get any signal to your TV without the preamplifier.
- If you now get some signals and you did measure correct voltage in step 9, above, then it's very likely that the long cable that runs from the antenna location, down into your house and connects to the power inserter is ok.
- You can also assume that the power inserter is ok.
- If you do get signals while the CM-7777v3 or CM-7778v3 removed, then you do need to consider the possibility that the preamplifier could be bad.
- Other considerations could be:
- Try a different coaxial cable between the antenna and the TV set.
- If there still are no pictures, try replacing the matching transformer/balun which is attached to your antenna. NOTE: Some antennas now have built in matching transformers.
- If this still doesn’t resolve the issue, it may be necessary to replace the antenna. However, it is not common for an antenna to fail completely. Its performance can become degraded over time if elements are damaged.
- Also, the interconnections between the antenna elements, can become corroded or damaged, but total failure is not common.
- Other considerations could be:
- If you know that you do have some strong signals at your location, but you still get no signals on your TV, then remove the power inserter from the system and connect a known good antenna to a known good coax cable, and connect that cable directly to a known good TV with a known good antenna tuner.
If you are still having difficulties with your preamplifier after performing the troubleshooting steps above, please contact Channel Master Technical Support.
- Select Contact Us towards the bottom of the page and describe the troubleshooting you’ve performed and the issues you are having in as much detail as possible.
- What does it do or not do?
- Please also provide your email address, telephone number, physical address, and date of purchase of your preamplifier.
- If you purchased your preamplifier directly from our website, please provide the order number. That will provide all of the info we need.
- If your Channel Master item has failed, please give us a chance to help you.