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Tekneek
join:2012-02-19
Bethlehem, GA

Tekneek

Member

Anyone had their own cable modem bricked by Comcast?

To make a long story short, I have been reluctant to purchase my own cable modem due to an experience (a few years ago) where a Comcast tech did a "signal test" in our neighborhood that killed our modem and our neighbor's modem (I watched him out at the box and right after that the modem failed to ever sync again. Comcast denied it over the phone, but when the tech came back out he knew exactly what was up and was prepared to swap out the modem from the start).

Has anyone here had Comcast do something that killed a modem you had bought? If so, has Comcast been willing to do anything about it? I know $70 - $80 isn't that much money in the big scheme of things, but I am not inclined to just absorb that when someone else is at fault (although being able to ditch the default gateway is tempting even with the risk).

telcodad
MVM
join:2011-09-16
Lincroft, NJ

2 edits

telcodad

MVM

Besides some kind of high voltage condition on the coax input, a problem with a modem firmware update can also "brick" them.

Not sure if this has ever happened on a Comcast system, but here are some DSLR news items I found about a bad SB6120 firmware update on Charter's system bricking modems back in May 2010:
»Firmware Update Cripples Some Motorola SB6120 DOC 3 Modems [49] comments
»Charter Exploring What Killed Many User Modems [48] comments

EDIT: Here's a thread about a modem bricked by a lightning storm: »Cable modem fried by lightning how to prevent again?
Tekneek
join:2012-02-19
Bethlehem, GA

Tekneek

Member

Those were an interesting read. I didn't turn those up in my searches prior to posting.

Glad to see they were at least talking about identifying the problem and dealing with it.

The "signal test" this guy did, which I never got a very convincing explanation about (but I don't know a lot about "cable company" operations, being an information security guy), apparently involved pushing an electrical charge through. The first two homes with cable modems, mine and my neighbor's, had our modems bricked immediately. As far as I know, the first and other nearby houses were on DSL and therefore had no problems. It has only happened once, over the 6+ years we've had cable Internet, but it was a frustrating experience.

I think I've convinced myself to go for it. While this event was not the same as modems being bricked by a firmware update, I hope that the way Charter dealt with that problem will mean that (in combination with being a Comcast business class customer now) they won't completely leave me holding the bag if they do something similar again.

Streetlight
join:2005-11-07
Colorado Springs, CO

2 edits

Streetlight

Member

I once watched a Comcast line tech move a pedestal that had been placed very near someone's driveway and had been driven over. The result was a fuse in the nearby Alpha box blew and took out the whole neighborhood. Anyway, while connecting up these large diameter coax cables, sparks flew all over, and I asked why. He said these cables carry, IIRC, 65 volts as well as the RF signals. I presume this electricity is to power downstream electronics in various parts of the system and doesn't get into cable drops to residences. This guy knew what he was doing as no damage was done. I can imagine if these large cables' conductors touched the wrong place in the ped, putting this voltage into the coax going to modems, they'd be fried. I'd also expect cable TV boxes and maybe splitters to also suffer, but who knows?

Also, one day we had a nearby lightening strike and the cable TV went off. Called CC, and a guy came to the door within 10 minutes. I told him what happened, and he went out to the ped and found a small circuit board had been fried. Literally. It was carbonized. Still have it somewhere. He had the correct copy in his truck. No damage to any CC equipment in the house, but a hole was punched through the case of our sprinkler system control box next to the transformer inside the box. Somehow the lightening energy didn't get to anything else. Lucky.

kara
@comcast.net

kara to Tekneek

Anon

to Tekneek
In the 90's I seen a corded telephone that was connect to at&t service lightning hit tree above the house grounded on everything wired in the ground and melted to wiring into the phone. Lucky was not talking on it.
rody_44
Premium Member
join:2004-02-20
Quakertown, PA

1 edit

rody_44 to Tekneek

Premium Member

to Tekneek
The tech doesnt do anything that puts a electrical charge on the line. Not anything that would damage a modem that is. The only way anything comcast does that would possibly put a elctrical charge on the line is if the area has a bad neutral in the electrical service of the area. And yes when that happens its not comcasts fault but a area electrical problem. The only electrical source even available to the tech is the 60 volts that runs the amps and no that 60 volts isnt bricking any modems. Your modem will handle any signal or voltage any of the tests involved. The OP is just plain wrong in his assumptions.
rody_44

rody_44 to Streetlight

Premium Member

to Streetlight
Comcast techs dont carry lightening in their pocket.
Tekneek
join:2012-02-19
Bethlehem, GA

Tekneek to rody_44

Member

to rody_44
All I can tell you is that a guy was down on the street, connected something to the box there, and our modems lost sync right then. I went out to talk to him and he said he was doing a "signal test" and that I needed to call it in. When the same guy came out a couple of days later, he already had a replacement modem with him.

And inserting a brand new modem resolved the problem immediately. The tech said the charge he put in must have killed the modems. I don't know enough about it to know what he really did, but it would be one hell of a coincidence.

Ebolla
join:2005-09-28
Dracut, MA

Ebolla

Member

He would of had a modem with him due to the fact that if he didn't and it was a modem issue then he wasted his own time as well as yours. This doesn't mean he KNEW when he went out that the issue was modem.
Tekneek
join:2012-02-19
Bethlehem, GA

Tekneek

Member

I was convinced that he had changed something down at the street, but he said he didn't need to check that or the signal levels. He said he knew he had killed the modem and just replaced it without any other diagnostics. I guess you guys know more about it, and the tech was just a crank pulling my chain.

NetFixer
From My Cold Dead Hands
Premium Member
join:2004-06-24
The Boro
Netgear CM500
Pace 5268AC
TRENDnet TEW-829DRU

NetFixer to Tekneek

Premium Member

to Tekneek
If you have an APC UPS, connect the coax from the Comcast network to your cable modem through the coax data protection connectors on the back of the UPS box. Other brands of UPS and surge protection may also have similar protection, but I have used the APC dsl and coax protectors with no problems, so that is the only brand that I can verify works with no problems.




Some techs may advise against doing this, saying that the protection connectors will add a significant db drop to your connection, but I have never noticed any modem stats changes when using any APC UPS data protection connectors for either cable or dsl connections.

telcodad
MVM
join:2011-09-16
Lincroft, NJ

telcodad

MVM

APC used to make a standalone coaxial surge protector »www.apc.com/resource/inc ··· e_sku=pv but it is now discontinued.

I think the TII 210 & 212 series of coaxial surge protectors »www.digicomm.com/tii210.pdf looks good.

Amazon carries the 212 model: »www.amazon.com/TII-Broad ··· 016AIYU6

NetFixer
From My Cold Dead Hands
Premium Member
join:2004-06-24
The Boro
Netgear CM500
Pace 5268AC
TRENDnet TEW-829DRU

NetFixer

Premium Member

said by telcodad:

APC used to make a standalone coaxial surge protector »www.apc.com/resource/inc ··· e_sku=pv but it is now discontinued.

I think the TII 210 & 212 series of coaxial surge protectors »www.digicomm.com/tii210.pdf looks good.

Amazon carries the 212 model: »www.amazon.com/TII-Broad ··· 016AIYU6

Yes, there are certainly other brands than APC, and not all are built-in to UPS boxes, and many of then "look good" from their specs.

However, I generally only recommend something if I have actually had experience using it (hence the APC caveat in my original post).

And of course, the universal caveat of YMMV is always appropriate.
Tekneek
join:2012-02-19
Bethlehem, GA

Tekneek

Member

Thanks. I will look into some of that.

Pretty strange event, apparently. Two cable modems failing precisely when a tech is mucking around with the box at the street. Him being sent out two days later claiming to already know what the problem is and demonstrating how the new modem syncs, and how the old modem won't (same model), and saying it was something he did (despite not being able to do that to the cable modems). I guess these two houses slipped into the twilight zone for a couple of days.

NetFixer
From My Cold Dead Hands
Premium Member
join:2004-06-24
The Boro
Netgear CM500
Pace 5268AC
TRENDnet TEW-829DRU

NetFixer

Premium Member

said by Tekneek:

Thanks. I will look into some of that.

Pretty strange event, apparently. Two cable modems failing precisely when a tech is mucking around with the box at the street. Him being sent out two days later claiming to already know what the problem is and demonstrating how the new modem syncs, and how the old modem won't (same model), and saying it was something he did (despite not being able to do that to the cable modems). I guess these two houses slipped into the twilight zone for a couple of days.

My guess as to what happened is that it was not caused by some standard test, but it was instead an accidental short to a high voltage line that blew the modems. I'm surprised that only two modems were zapped (but of course there may have been more damage that you were not made aware of).
Tekneek
join:2012-02-19
Bethlehem, GA

Tekneek

Member

That makes sense. The tech probably didn't explain it well enough. Any of the stuff before it gets into the house is their game (and I don't always know my way around it).

SeaSeaTee5
join:2010-05-06
Maryland

SeaSeaTee5 to Tekneek

Member

to Tekneek
Sound's to me like he trapped both lines for ingress, but I expect that he wouldn't just swap the modem on the service call without fixing the original ingress issue first.
Tekneek
join:2012-02-19
Bethlehem, GA

Tekneek

Member

If he did, he didn't fix it that day. I met him outside, anxious to get things going again. What I wouldn't know is if he came out the day between, because I had to work from a coffee shop all day!

I tried to get him to check that everything was right at the street, but he said he already knew it was fine. Suppose he did repair that some time previously himself, explaining his certainty over the whole thing. I only wish he had swapped the modem the day it happened rather than making me do the call in process.
westom
join:2009-03-15

westom to Tekneek

Member

to Tekneek
said by Tekneek:

The tech said the charge he put in must have killed the modems.

Which is why cable must connect to your single point earth ground before entering the building. If not connected to a common ground or is not even earthed, then charges could cause damage.

Comcast et al recommend no protector on their cable because, in part, that earth ground does much better protection than any protector. You can inspect this critically important ground. It should be to the same earthing electrode used by AC electric. It solves a long list of potential problems. But some techs do not take it seriously. "The cable worked just fine so that ground really was not important." And then you learn what can happen.

telcodad
MVM
join:2011-09-16
Lincroft, NJ

telcodad

MVM

said by westom:

Comcast et al recommend no protector on their cable because, in part, that earth ground does much better protection than any protector.

The way I see it, there are 2 issues - one where problems/damage is due to "Ground Potential Difference" [see: »www.duke-energy.com/indi ··· p-08.asp (which you referenced in this thread »Re: Surge Protection Residential Whole House )], where proper grounding and bonding come in, and another where damage occurs due to differential voltage surges between Line, Neutral and Ground (power) or between inner conductor and shield (coaxial cable) or between twisted pair lines (telco and CAT 5/6 cables).

Surge protectors, like the TII coax ones I mentioned above, help in the second case.
westom
join:2009-03-15

westom

Member

said by telcodad:

Surge protectors, like the TII coax ones I mentioned above, help in the second case.



Surges that do damage find earth destructively via electronics. You have discussed another transient; typically made irrelevant by protection routinely found inside all electronics.

A protector adjacent to electronics is for a typically non-destructive type of transient. Properley earthed wires (either directly like cable or via a 'whole house' protector like AC electric) means all types are transients are made irrelevant. But none of that works if single point ground has been compromised.

Protection increases with increased separation between protector and appliance. Protection also increases with shorter (lower impedance) connections to earth.

Earthing alone would not explain the OP's damage. But proper earthing means that damage would not happen.

A typical reason for such damage would be averted by proper earthing of that cable. Then protection routinely found inside all modems would not be overwhelmed.

Proper earthing (either directly or via a protector) means all types of destructive transients are made irrelevant. That is the first thing checked when damage occurs.

Problems could exist elsewhere. But a most common reason for damage is defective or compromised earthing. A defect so easy to locate - only observation is necessary.

telcodad
MVM
join:2011-09-16
Lincroft, NJ

2 recommendations

telcodad

MVM

said by westom:

Surges that do damage find earth destructively via electronics. You have discussed another transient; typically made irrelevant by protection routinely found inside all electronics.

While some quality brands of certain electronic items may have built in surge protection (like MOVs across its inputs, and maybe even RFI filtering), I don't know if that is "routinely" done in a majority of them, given how most manufacturers these days cut corners wherever they can to save a few pennies. I think many static-sensitive chips/devices may use Zener diode protection on their inputs, but that will not protect against more powerful surges.

I think what may have happened in the OP's case is what NetFixer See Profile said:
said by NetFixer:

My guess as to what happened is that it was not caused by some standard test, but it was instead an accidental short to a high voltage line that blew the modems. I'm surprised that only two modems were zapped (but of course there may have been more damage that you were not made aware of).

Grounding/bonding of the coax shield of a cable drop would not protect against accidental, transient contacts of the center conductor with high(er) voltage sources or leakage paths.
westom
join:2009-03-15

westom

Member

said by telcodad:

While some quality brands of certain electronic items may have built in surge protection (like MOVs across its inputs, and maybe even RFI filtering), I don't know if that is "routinely" done in a majority of them,

You have assumed MOVs are inside. In fact, manufacturers mostly stopped putting MOVs inside appliances. Because it did not protect from typically destructive transients. And because other solutions do better.

Even 1970 design standards for electronics required 120 volt appliances to withstand 600 volt transients without damage. Today, most electronics appliances will withstand approaching or above 1000 volts. Making most transients irrelevant.

Transients that might cause damage on the center conductor are made irreelvant or less significant how by cables work. The engineering details have no place in a layman's discussion where each type of transient (with numbers) must be defined. Meanwhile, galvanic isolation and other solutions routinely inside modems make most transients irrelevant. But protection can be overwhelmed if single point earth ground is not properly implemented.

A common mistake is to assume protection means MOVs inside an appliance. Too many confuse protector devices with protection. Those are two completely different items. The first step to eliminating future damage is an examination of what does protection - earth ground.

I believe Comcast now uses a voltage higher that 60 and less than 100 volts. But standards that have existed longer than anyone here required that modem (and other comunication equipment) to even withstand 300 volts without damage.

How could a higher voltage exist? One reason (and not the only one) is defective earthing at the service entrance.

telcodad
MVM
join:2011-09-16
Lincroft, NJ

telcodad

MVM

said by westom:

said by telcodad:

While some quality brands of certain electronic items may have built in surge protection (like MOVs across its inputs, and maybe even RFI filtering), I don't know if that is "routinely" done in a majority of them,

You have assumed MOVs are inside. In fact, manufacturers mostly stopped putting MOVs inside appliances. Because it did not protect from typically destructive transients. And because other solutions do better.

Actually, instead of MOVs, it appears that "Transient Voltage Suppressor" (TVS) diodes are/were used in many electronic devices (»www.littelfuse.com/produ ··· des.aspx). Littelfuse even shows an application for a "Set Top Box" on their site »www.littelfuse.com/techn ··· box.aspx
said by westom:

How could a higher voltage exist? One reason (and not the only one) is defective earthing at the service entrance.

Exactly, that's why the use of external surge protectors may still be necessary.
westom
join:2009-03-15

1 edit

westom

Member

said by telcodad:

Actually, instead of MOVs, it appears that "Transient Voltage Suppressor" (TVS) diodes are/were used in many electronic devices

Sometimes. Sometimes not. MOVs (as in many protectors) have too much capacitance - diminish signals. Only some semiconductor protectors are acceptable. But again, the point. Best protection at the modem is already inside a modem. Numbers provided to define it.

Some facilities have best protection without any protectors. But in every case (with or without protectors), protection is always defined by and requires earthing. The external protection. That earthing is a first thing inspected should damage occur.

About ten years ago, Comcast retrained all techs in these concepts. Sometimes, a tech does not get it. I discovered one location where earthing was installed defectively. After repeat failures, a tech even disconnected earth ground rather than fix an obvious defect. Even a few Comcast techs do not get it. Many assume solutions in a protector rather than learn the need for protection - earth ground.