Since I bought my iMac in May there have been 3 cable outages, the most recent a few days ago and this morning, and each time the machine turned off. I have to unplug it, then plug back in in order to turn it on.
After being a Windows user for 10 years, I was cautious re: "improper shut down" events, especially as I had pages open when the iMac shut down when the cable did.
A UPS that will power a single Mac is under a 100.00. I have a APC BACKUP-UPS 350 and it has enough reserve to get by the glitches and plenty of time to save my work. The BACKUP-UPS 500 would give you some more breathing room and it is 79.00 USD on Amazon.com
One electric meter for this entire dwelling. The breaker panel is in my place.
Although I bought 2 new surge protectors for setting up this wonderful iMac in May, I plan to replace the one in which the power connection was originally. I do want a battery back-up one, but they are pricey. So I might end up comparing the prices for those versus a whole house one installed by an electrician.
My other home was built in 1924. I had an electrician check that the outlets were properly grounded, though they had the 3 pronged covers. All were, except one. And wouldn't you know it was the one that served my PC.
Ok. Is the apartment fed off the same electrical service as ths house (same breaker box?) or is it seperate.. i.e. a seperate electic meter? It sounds like Comcast has covered their side. The fact they disconnected the cable and the computer stayed on rules out issues in the computer or network wiring. Good luck on this one.. I was originally thinking an old house with some prior do it yourself wanabee doing some wiring.... like mine!
To your first question, whenever there is a cable outage my TVs get the "snow", and a loud hum. This has happened ever since I have had cable from the Viacom days. (I became a cable subscriber when it first became available here. It started with Viacom, then Excite, then Intermedia, as I recall.) I usually turn them off because of the sound, but if not, they may later go to black. This is usually true of my 2 TVs with digital boxes as the one with only basic usually turns off.
I called AppleCare, and the tech spent a good while investigating. It was then suggested that perhaps my modem should be replaced. I have had the modem since between Excite and Intermedia, when I used a W95 PC with Pentium I. She also advised moving the power connection to a separate surge protector I have for my printer. (First suppressor had the power cord. modem. and my camera dock plugged in it. The second had only my printer.)
I moved a little more than 4 years ago, and this is new construction, dedicated electric outlet. and all cables are "home runs". The problem with the cable outage did not happen with my WMe, Pentium III PC.
So I called Comcast. A field tech and one in training arrived, and spent, again a good while checking various components. He disconnected the cable connection from the modem (the iMac did not turn off), and connected some gadget to it. Used some gauges. He checked the box outside, said the put in a new splitter (the one that splits the cable from the street between my son's house and my apartment tat is attached to his house) and changed some "connections". He also went to the street, and changed some "connections" there.
There is also an amplifier.
(My son's XP PC does not turn off with a cable outage.)
He then connected a new modem.
About a year ago the Comcast construction department replaced the cable from the street pole to the house with a "heavy duty" one.
I don't know if the problem is solved, and won't until there is another cable outage. Those usually occur in the mornings. (In the past there would be a notice that the lines were being "washed".) This last time the first was less than 5 minutes, the second was about 1/2 hour.
So I will wait and see, especially as there have been no problems with the electrical service and the wiring was inspected during construction.
Just a bit of humor here.... The AppleCare tech said there was a case of a person who had his Mac plugged into the same receptacle as his refrigerator. Every time he opened the refrigerator door, his computer turned off.:-)
There is nothing under normal circumstances that would cause this to happen. The cable disconnecting will not and can not shut your computer down. I suspect that whatever is causing the cable to disconnect is also causing your computer to shutdown. Power supplies in computers are senstive devices and will shutdown under abnormal power conditions.
What "noise" does your TV make when the cable goes out? Mine just goes black, no noise.
I am going to suggest you have a significant electrical problem in the either the cable wiring or the power wiring in your house. If you really are sure there has not been even a millisecond interupt in the power, then hire an electrican and have this checked out. Improper balances in the power or volatage on your ethernet or cable coax may cause odd issues and it may cause permanent damage to the TV or your computer. Other possibilites are a ground leakage in your house wiring, voltage on the neutral or other issues within your power distribution. These can cause personal harm or worse. Such issues can be caused by a faulty appliances (usually one with significant current draw (motors, heating devices or devices with heaters in them, refridgeratrs, etc. ). which develop an internal electrical leakage. The problem may only occur when they cycle on. It could be due to bad or aging wiring or connections or leakage between the power system and the cable system in your house.
Do you also have phone line plugged into the modem? (The regular telephone modem in the computer, not your cable modem... newer Mac's except laptops don't have modems so this may not apply).
In all seriousness, have an electrican check this out as soon as possible.. and buy a UPS for you computer, it will add at least one additional layer of protection.Edit
Edit: Add: iDisk is not the issue here. I use it all the time.. if it can't connect it simply waits until it can.
I'm having a hard time imagining any way that a cable outage would even be detected by the computer, much less cause it to shut down.
Do you use iDisk? I don't know much about it, but I suppose the computer has to check the server at Apple for changes every few seconds, and this would fail when the cable goes out. But I'd expect the software to simply ignore the error and try again later; if this is causing your computer to crash there's obviously a problem.
None of the events have been due to electrical power outage. The cable-connected TVs and the computer are the only ones.
Yes, I do have a surge protector for the computer and the cable modem, and and a separate one for the all-on-one printer.
What I have unplugged is the computer. The first time my initial step was to reset the modem (disconnect, wait several seconds, re-connect) but that didn't work. So the next 2 times I only unplugged the computer.
It may have been a power outage and perhaps you should have a surge protector for your iMac. I assume that your computer is connected via a Comcast modem to the cable. Do you unplug the computer, the cable modem, or what? Do you disconnect it from electrical power or from the cable? sam