Comcast Internet Repair

Comcast internet service is an excellent value. Yet, the Comcast network is complex. Follow us as we guide you from ordering the proper service, modem settings, your building coax plant, to finally outside coax transmission lines and fiber node issues.

We Require Business Grade Internet Service

Modem Performance Issues

comcast repair

Your Building Coax Cabling Must be Perfect

Verify Signal Quality Levels in Your Cable Modem Diagnostic Page

Comcast service delivery is like municipal water service delivery. It's a system of interconnected large and small diameter pipes. Comcast states that a working "water pressure" range is -15db to +15db with lower than -11db as being in the "yellow range". Unofficially, Comcast insiders state it should be at 0db for best performance. The picture below shows a Comcast SMC8014 cable modem diagnostic page with very low downstream power but acceptable (SNR) signal to noise ratio.

Good SNR is especially important if the downstream power can not be improved. Inside cabling defects such as a loose connection to a TV can cause poor SNR. On critical or new cable modem installs, we will discourage connection of cable TV until performance is proven. It is the customer's responsibility to correct any deficiencies on interior cabling.

You can't measure upstream SNR but you can extrapolate it by the upstream power the Comcast CMTS (head-end) commands the modem to transmit to push it's signal back to Comcast.


This is the View from Your Cable Modem Diagnostic Web Page:

comcast repair graph

Verify Signals with Comcast: (This Gets a Trouble Report Made)


Above modem performance must be within normal bounds for a week according to Comcast Scout or Grandslam systems.

Typical Scout Report health Check Report:

These reports show data marked as green, yellow or red. This report is all green.

IP Address of Modem
Current CMTS Status ACTIVE
Current Firmware
Device Make/Model SMC Networks SMCD3G-CCR
Device Up Time 104 days 9:14:35.05
Docsis Capability DOCSIS 3.0
Downstream Signal Quality (SNR) 35.0
Modem Lost Syncs 1
Modem Resets 5
Receive Power Level (downstream) 0.1 Dbmv
Receive Power Level (upstream) 2.8 Dbmv
Serial Number of the Device H29421C3C4
Transmit Power Level (upstream) 48.0 Dbmv
Upstream Signal Quality (SNR) 32.0
Current Device Status  6(Online)
End of Life Status No
Modem Boot File
Your signal quality goal....
Minimum specs Best we have seen
Down Power in >= 0 db 0 db
Down Signal-to-noise (SNR) > 32 db > 37 db
Up Power < 42 db < 35.5

Ground the Cable per National Electrical Code Section 800-33


Ungrounded Box

Above picture shows a Comcast Box that has NOT been grounded. Arrows indicate where grounded connection should be.

Mainline Tap Problems

two position mainline tap plate


Pictured above is a cable mainline connected to a mainline amplifier and to the right a two position mainline tap plate. Two RG-6 coax drops come off the tap plate. One has a blue tag and the other has a yellow tagged HBO channel filter.

In this picture, installing a new (third) connection for a new customer would require the independent installer to first call the cable company to convert the two (2) position tap plate to a four (4) position tap plate, then the installer would need to make a second trip.

Or, to get his "paid per the job" install done, the installer may install a 2-way indoor splitter and then call the office to get the main line tap plate changed.  On the later scenario, the customer who gets split, may be forced into a marginal power level condition. Plus, they will have two unexpected service interruptions. Once the single available connection is split, the second when the tap plate is properly converted to a 4 tap plate and then the new connection dedicated to it's own tap. They may also have marginal power levels and thus marginal service in between splits.

underground two position mainline tap plate

Pictured above is a four position mainline tap with one unused position properly capped to prevent RF intrusion. Orange RG-6 direct burial cable is used. The cable may turn yellow with age and exposure to the sun's UV rays.

Inspect your building drop from the mainline tap and insure that none of the above issues exist. 

Node Problems

At some point past the copper coax main lines, the copper coax coverts to glass fiber lines. This is called the fiber node. These nodes can misbehave and cause problems for your neighbors and you. A fiber node feeds from 25 to as many as 300 businesses. 

We have software that can detect these node problems by analyzing your Internet and those of your neighbors. We then correlate issues.

Refer Us to Comcast Users Next Door, We Both Benefit

We certainly love business referrals. Referrals to your neighbors are the #1 thing you can do to help monitor complex Comcast quality issues. When we see simultaneous issues from 3 or more otherwise healthy Comcast subscribers on the same node, we can submit an engineering ticket to Comcast to check the areas for issues.