CM-7777 CM-7778 Troubleshooting;
Also see attached diagrams at the bottom of this article;
- 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, to the “INPUT” port on the CM-7777/CM-7778 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-7777/CM-7778 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 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 approx. 13.5VDC if your power supply is the 12VDC version adaptor.
- The voltage should be approx. 21VDC it you have the 15VDC version supply.
- The voltage spec is on the label of the Power Supply Adaptor.
- Both of these power adaptors work equally well.
- 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 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 (from the Preamp) to the “TO AMP” port of the Power Inserter.
- 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 Preamp.
- However, you can use DC/Power Passing splitters. You can find them here.
- Disconnect the coax cable from the preamp ‘OUTPUT/POWER” port and measure the voltage at the end of the coax cable.
- 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-7777 or CM-7778 preamp.
- 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.
- Remove the preamp and connect the long coax cable directly to your roof Antenna.
- Leave the Power Inserter in the system.
- The coax cable that is connected to the “TO TV” port of the Power Inserter should be connected directly to a TV. (A TV With an ATSC HD TV Tuner)
- The Power Inserter “TO AMP” port should remain connected to the long coax cable going up to and connected to your roof antenna.
- In most instances, your stronger signals will be present and detected by your TV.
- 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 the long coax cable from the antenna, directly to your TV.
- If you still do not get any signals, check your connections and try other cables if you have them.
- If you do get signals while the CM-7777 or CM-7778 and the Power Inserter are removed, then you do need to consider the possibility that the Preamp and/or Power Inserter is 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 balun/matching transformer which is attached to your antenna. Please 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 elements, can become corroded or damaged, but total failure is not common.
If you are still having difficulties with your preamplifier after performing the troubleshooting steps above, please contact Channel Master Technical Support here and describe the troubleshooting you’ve performed and the issues you are having in as much detail as possible. Please also note 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.
Thank you for your time!
Channel Master Technical Support.