Now this is a strange problem…

Someone emails me, saying his laptop will dial up his internet connection, but only if he is running on battery power. If it is plugged into the AC adaptor, he cannot dial his ISP.

I think of the usual suspects: malware/virus, windows power settings, a faulty power supply.

After some testing, I also found that if I connect to the internet (whilst on battery power), and then connect the AC power, the modem hangs up. At that point, I pickup the phone, and a hear a buzzing noise (probably 50Hz)…

I get the feeling that the AC ripple from the power supply rectifier, is not being filtered properly and is making its way to the modem (or the power supply has a faulty rectifier or capacitor… unlikely, as I measured the voltages, and it is DC, with very little AC component).

Anyway, I dismantle most of the laptop, looking for something obvious (like an exposed wire touching somewhere it shouldn’t)… but no such luck.

I’ve never liked laptops much, and my experience over the last few days has reinforced my bad feelings.

This looks like a job for Acer technical support (who will most likely just replace the motherboard).