@Framiga
thats are "schuko" type plugs.
Right.
Anyway check with a mutimeter (continuity check) if that clips AND the center hole of the 3 holes plug, are phisically connected.
I just did and.. oh-oh, they are physically connected! All plugs in the house are like that. I suppose that this is a bad thing and it means that i don't have a real earth, right? :-?
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@Floid
1. Is the smoked transformer IC on the phone side or the ethernet side? If it's on the phone side, you can rule out ethernet mysteries.
Good thinking. The smoked IC is on the ethernet side. No doubts at all. That's why i suspected that there is something wrong with my Amiga from the beginning.
In fact, that modem can still detect the DSL line, but not the ethernet connection.
2. Certain Speedstream modems, as I found out the hard way, can get into an inexplicable kiss-of-death scenario with certain systems. This happened to me with a 5360 when I happened to hook up a Netgear WGR614 in place of another router. However, in my case, the modem could be observed rebooting every minute or so. (Presumably some relatively common network activity looks like a firmware flash command to the modem; there's a nearly forgotten Windows utility to reflash the 5360, YMMV with a different model. I never tried it since I didn't have a Windows machine around.)
That's possible, but i never observed this behavior while i was still able to communicate with it. My bet is that the Speedstream got damaged, just like the SpeedTouch.
The coincidence is pretty inauspicious, but it could have just been one instance of defective hardware followed by the strange Speedstream bug. I'd sacrifice one more modem to it, of more recent manufacture, to find out.
I'm on it. It's not that i have other alternatives. :-(
I wish i could pin-point what is the problem first.
Oh, and re grounding/earthing: The 1200 has a ground, but those modems all run off wall-warts, and unless your locale has significantly different regulations, the wall-warts are two-pin devices.
That's right. Both modems came with two-pinned "wall-warts".
You could have dirty power or the 1200's supply might be providing dirty DC to the PCMCIA slot, but that strikes me as less-likely if the Speedstream problem is what I think it is.
It's not the PSU. Like i said earlier the first modem got burned while i was using a A500 PSU, and now the second one stopped working while using a pc PSU.
If you're really paranoid about the NIC possibly taking out the modem, I suppose you could put a $10 hub between the modem and computer. Unless the hub fails and takes something out with it. 
A hub? I will have a look at hubs. Because from what i have observed so far, this is what is happening. The NIC or the Amiga is damaging the ethernet circuit of the modem.