Thank you for being a valued part of the CNET community. As of December 1, 2020, the forums are in read-only format. In early 2021, CNET Forums will no longer be available. We are grateful for the participation and advice you have provided to one another over the years.

Thanks,

CNET Support

General discussion

2 more incidents of iMac shutting down at cable outage

Sep 8, 2007 6:22AM PDT

(OSX.4.10 Safari 2.04.4)

Once a few days ago, and again yesterday morning. The iMac shut down (black screen) simultaneously when TVs suddenly lost cable. (No electrical power outage.)

First I posted in my ISP's Macintosh forum. Apparently no one else has had the problem so far.

I phoned AppleCare, and spent some time with the tech. I had the modem plugged into the same surge proctor as the computer and my camera dock. She advised moving it to the surge protector for my printer. She then opined that the cable modem was sending a surge. I have had this modem for several years, perhaps as many as 7.

Today I called my ISP, and am scheduled to have a new modem delivered Monday morning. What bugs me is that the tech talked about what might have to be done.... changing cables inside and out, etc. that would cost almost $40/per hour., which tells me the guy Monday will do all he can to say I don't need a new modem.

So I'm wondering if the best way to duplicate the problem would be to unplug the modem from the power source, or disconnect the cable from it.

Thanks!

Angeline

Discussion is locked

- Collapse -
P.S.
Sep 8, 2007 6:26AM PDT

Both times the machine would not turn on after the cable was restored. it was necessary to unplug it from the power source, plug it back in, then all OK.

Angeline

- Collapse -
Just fyi
Sep 8, 2007 6:34AM PDT

Ethernet doesn't have a direct connection to the electronics. Here's the schematic.

http://www.amphenolcanada.com/ProductSearch/pdf/RJmag_CAT.pdf

Notice there are no direct connections from the ethernet cable connections to the circuitry on the NIC? As such between this and the fact that ethernet allows quite a jolt without upset I'm going to write it's not coming from there.

Bob

- Collapse -
Your skills and knowledge far exceed mine.
Sep 8, 2007 7:36AM PDT

That puts me at the mercy of what I am told/advised when I contact tech support. ;-(

From what you have said, does that mean it is possible that I have a "bad" ethernet card?
Somehow it seems if that were so, the tech would have mentioned it.

So I guess it could be some internal something. Sure is depressing.

I wouldn't be so concerned except that I've had pages open when these happened.

BTW, the computer has a dedicated line. It and all of the TVs have "home runs" from the box. No splitters.

Thanks, Bob!

Angeline

- Collapse -
Sorry.
Sep 8, 2007 7:43AM PDT

I only wanted to share that nugget. Ethernet or 10/100BT is built to take quick large jolts. Part of the reason is that you never know what you'll pick up over a few hundred foot run.

My hope was that you'd look at other areas.

Bob

- Collapse -
No need to be sorry.
Sep 8, 2007 9:03AM PDT

You gave me a visual picture re: what is connected to what.

As for looking in other areas, I have presented the problem to my ISP forum and ISP tech support, and AppleCare. I reckon my next move will be local Apple service. I also tried a Google search. May not have asked the right question, but no luck. Lots of info on power failure, but not cable. These are all of the avenues I have.

I did read re: the "logic board". but that was included in the power supply bt.

I do appreciate your help.

Angeline

- Collapse -
Shut downs
Sep 8, 2007 8:40AM PDT

Hi,
I, too, can see no reason why the mac would shut itself down when the cable went south.
Apart from the ethernet cable, they are not connected in any way. As Bob mentioned, this would not shut the machine down.

I do have a question though.
Is it possible that the power to the modem/computer (from the same surge protector) is being interrupted in some way. Strange that the TV should go off at the same time though.

Cable replacement is an ISP thing and will/should cost you nothing! There are plenty of devices that measure the strength of the TCP signal so they should be able to tell you where the problem is.
The ISP should be responsible for the cable all the way to the first TV/Computer.

Before this guy arrives, unplug the cable from the modem. See what happens.
I'm betting that since the modem is no longer connected to the same surge protector (is it that or just a strip with more than one outlet in it?), the problem will not happen again.

P

- Collapse -
I bought new....
Sep 8, 2007 9:38AM PDT

....... surge protectors with my new set-up, and though they are strips, they are not the ones some folks use in their kitchens or work shops. They are labeled "computer surge protector". Each is plugged into the individual outlets on a standard duplex outlet, but it is a dedicated circuit.

I read about the USP protectors, and remember your advice about buying the battery back-up, which I will when I save up the $$. They are not cheap.

I looked at some logs, but couldn't find what looked like might be help.

I have 3 cable-serviced TVs.... 2 with digital boxes, one without. They are in different rooms, and all went out simultaneously, as they always do with cable outages. My PCs never did, except the 'net could not be accessed.

Like I said earlier, AppleCare did recommend plugging the modem into the other protector. So it is possible that will solve the problem.

But I'm taking the new modem. it's smaller than the one I have. Happy

Thanks!

Angeline

- Collapse -
Udate on cable outage problems
Sep 10, 2007 1:32AM PDT

My ISP guys just left. I got the new modem. Happy

They checked everything from the house to the street. Replaced some fittings both places

(Interesting in when they disconnected the cable at the house box, the iMac did not lose power as before.)

They said they honestly could not say what the problem was, but that I did need a new modem as mine was so old.

So we'll see if it happens again. I do think due to the iMac not being turned off this time says the problem was somewhere in the cable stuff.

Thanks!

Angeline