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Apple Desktops Discussion of Apple's desktop machines including Mac Pro, iMac, Power Mac, and mini

Trouble with "cable not connected" error


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aLotus

 
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I've been struggling to get to the bottom of a wired connectivity issue which started earlier today. My internet connection dropped out and the modem/router rebooted (because of a problem at the exchange). Since then I have not been able to get my iMac wired connection working.

Here's what I checked so far:

All LAN ports on the router work (tested with a PC)
The cable works (also tested with the PC)
Connecting using AirPort works
Apple Hardware Test shows the ethernet port's MAC address in the hardware profile and the tests show no problems.
I've tried to change speed and duplex settings manually but nothing seems to get rid of the error.

I really want to be able to use a wired connection because I don't get a high enough speed for some things with AirPort.

Could anyone suggest what I should try next?
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Adric

 
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If it were me, I would call my ISP and have them walk me through what to do. It sounds like some sort of conflict with the IP address and your computer which only your internet provider can go into with any sort of depth.

Give them a call!
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aLotus

 
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Quote:
Originally Posted by Adric View Post
It sounds like some sort of conflict with the IP address
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... but I neglected to say, the LAN is NATed.

The router uses a 192.168.1.0/24 private address range on the LAN side. DHCP on the router is working (both the PC and AirPort connection show that) but I have also tried setting up the port with a manually entered IP address.

On the WAN side, there is no problem now. I spoke to my ISP about that but the drop-out only lasted a short time anyway.
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aLotus

 
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I've changed the subject slightly as the quoted message in the original was not accurate (it was a combination of two different messages "Ethernet not connected" and "cable unplugged").

Update:
I couldn't find any documentation on the differences between the standard Apple Hardware Test set and the extended test set but just in case it may reveal something I ran the extended set. 2.5 hours later! it finished and reported no problems. So I'm no closer to finding the cause.
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BSD Meister

 
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AHT only tests the interface circuitry, not an end to end connection (unless things have changed). If the system is telling you that there's no cable connected then that's what it SEES the problem as being (that doesn't mean that's it though).

The solder connections to the I/O connector on the logic board can break or crack fairly easily if forced, however another culprit might be the connector where the ethernet cable plugs in itself. Sometimes when removing a cable and connector, the fingers inside the connector can catch and bend in such a manner that their fingers are no longer in the right places. Look at the ethernet connector on the iMac and see if they look like any of the metal fingers are bent, out of place, or pushed far enough down that they're not making contact. If they aren't, be very carefully trying to manipulate them back into place. For your model (iMac 9,1) the I/O ports sit on a plastic deck on top of the logic board. I don't know if it's repairable besides replacing the logic board (it's not a standard Apple procedure, but some things Apple offers as solutions are done to speed up repair, not keep costs down).

When you lost your connection earlier, it's also possible that the driver stages of the interface got blown if they were hit with a transient. I would think AHT would catch it but I've seen cases (on FireWire) where they didn't.

Good luck.
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aLotus

 
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Thanks for the reply. That is useful information.

I checked the connector visually from the outside and there is no sign of anything unusual. I have always been very careful when inserting and removing cables so would have been surprised to see physical damage. For the same reason, and the fact that failure happened without the machine being moved or even touched, I would be surprised if the solder had failed (but of course can't rule it out until I check). At the moment I don't have the tools to open the case myself (no suction cup puller) but even if I did a visual check wouldn't necessarily be enough to identify solder separation.

I'm inclined to think it may be that the driver stages were damaged. I didn't mention it in my original post but the connection was lost during a thunder storm not a power outage or reboot caused by a software glitch. I doubt any significant electrical surge could have passed through the modem/router without damaging it (neither that nor the PC which was connected at the time suffered from any physical problem) but it is not beyond the realms of possibility.

If logic board replacement is needed I'll just leave it as I don't the gain in network speed is worth the cost. As I'm somewhere between 1.5 and 2 hours drive from the nearest Apple service centre I think I'm going to have to live with it for a while anyway.
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Just a WAG here after the very useful response from BSD, but did you try resetting the SMC and the PRAM?
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aLotus

 
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I hadn't tried resetting either because I didn't think there were any settings which would affect the ethernet port in NVRAM, but as you suggested it I reset both.

Unfortunately, there's still no change. Thanks anyway.
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BSD Meister

 
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Quote:
I'm inclined to think it may be that the driver stages were damaged. I didn't mention it in my original post but the connection was lost during a thunder storm not a power outage or reboot caused by a software glitch. I doubt any significant electrical surge could have passed through the modem/router without damaging it (neither that nor the PC which was connected at the time suffered from any physical problem) but it is not beyond the realms of possibility.
Electricity follows the path of least resistance. What appears to make sense often doesn't. It's like water flowing from a leaking roof. I had a leak in my roof and wasn't aware if it until I saw water dripping onto the basement floor near a drain pipe! Sometimes it's obvious, sometimes it isn't. An electrical "spike" typically has a lot of very high frequency components that can work their ways around "common sense" paths...they don't go where you think they would go. The output driver stages of a chip are analog and if destroyed only an end-to-end test or some type of test with a loopback connector would verify it...and you might still get the "no cable connected" message. Internal hardware tests can't detect them because they don't measure output or input on the analog drivers.

I understand your preference for hardwired vs. Airport, but hey, the Airport isn't THAT bad. Be thankful it didn't take out your whole system.
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aLotus

 
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Quote:
Originally Posted by BSD Meister View Post
I understand your preference for hardwired vs. Airport, but hey, the Airport isn't THAT bad. Be thankful it didn't take out your whole system.
Indeed, it's always frustrating to have something that fails but at least I have all the functionality I need and a machine that boots

At some point I will take it to be tested and will update this thread just for information.
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aLotus

 
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Just to round off the thread here's the outcome of my visit to the Genius Bar.

The only test done which I had not already done was to boot from an external drive to rule out any potential software problem. Apparently a more detailed hardware diagnostic can be run for other problems but they run it via the LAN port so for a LAN port problem it's a non-starter. The fix is a replacement logic board which would cost about 650 GBP and leave me without the machine for 10 days.
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