CM1200 Downstream blinking with sync loss

[JTam365]

Downstream is always blinking green meaning loss of sync.  It is always the same channel not locking.  513mhz.  Power levels look good except for slightly high upstream.  See attached.  No splitters in line.  Is it bad line to the CMTS on the upstream?  Upstream power only went high after ISP drained water out of their junction box!

[JTam365 · Accepted solution]

Solution:  ISP tech showed me where he was getting all green on his line check.  Said it was probably the modems error.  After I said it was only 1 channel not locking and high upstream power he made a phone call and hooked up a spectrum analyzer and found a bad channel on his side.  Called in a lineman who found a bad amp inline.  Now getting no errors and all power levels in spec!  Note: Blinking downstream led is a good indicator of high upstream power (modem is shouting to the CMTS)

[FURRYe38]

Power levels are a bit too high:

https://kb.netgear.com/24311/Power-level-guidelines-for-a-NETGEAR-cable-modem-router

I'd ask the ISP if they can turn that down some.

Have the ISP review and resolve the Criticals and Warnings seen in the event log.

You have lots of correct and uncorrectables on channel 1. Those should be zero as the other channels. 

Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 
Start with removing any amplifiers, signal attenuators, or splitters from the coax.
From there check the line for kinks, damage, moisture in the line.
Check the connectors for improperly made ends, foil touching the copper coax line, loose connections, bad/old/cheap connectors, or corroded connections. Replace them if you do.
Be sure to power OFF the modem for 1 minute then back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...

Be sure your using a good quality LAN cable between the modem and router. CAT6 is recommended. 
What is the brand and model of the host wifi router connected to the modem?

[plemans]

You've got errors in the line and errors in the log. If they had water in the junction box, they should look at it again. 

[JTam365]

Router is Netgear R6700AX wired with cat6.  Will try to bypass my home CATV wire with cat6.

[FURRYe38]

RG6 coax cable is needed from the ISP service box up to the modem. 

Then from the modem to your wifi router needs to be LAN cable, CAT6 recommended. 

If have your ISP check and review the suggestions given...

[JTam365 · Accepted solution]

Solution:  ISP tech showed me where he was getting all green on his line check.  Said it was probably the modems error.  After I said it was only 1 channel not locking and high upstream power he made a phone call and hooked up a spectrum analyzer and found a bad channel on his side.  Called in a lineman who found a bad amp inline.  Now getting no errors and all power levels in spec!  Note: Blinking downstream led is a good indicator of high upstream power (modem is shouting to the CMTS)

[FURRYe38]

Glad you got it working. Thanks for letting us know.

Enjoy.