24” iMac 2.8 GHz Intel Core 2 Duo OSX v10.5.5 shutdown anomaly.
I have noticed that when my iMac shuts down, that initially the One Touch Maxtor 500G external drive attached to the Firewire 400 port also does a normal shut down and the light goes out. Within a few minutes I noticed that the light on the Maxtor is back on. This does not happen if I use the USB 2.0 port to attach the hard drive and iMac, the light remains off. It appears the FW400 port is active on the iMac even when in the shutdown mode. Is this normal for the iMac?
I have a 13”MacBook 2.4Ghz that does not activate the same Maxtor when it is shut down. I attach it via the MacBook FW400 port.
I hooked up an ammeter to the iMac power cord and observed the following readings:
iMac Off: From 50ma to 180ma cycling at a rate of 23 cycles/minute. Using the Watt reading of the instrument, that amounted to cycling from 0 to 5 Watts every 4 seconds.
iMac On: 1.16A 133Watts.
This iMac is new, 1 week old, does it need repair or is this normal? I like to get a FW800 external HD, but I don’t want to have to pull the plug on the HD every time I want to shut down.

Thanks
Mike