A few owners of the Duo 270c, 280, and 280c have encountered a perplexing problem: every so often a Duo becomes "addicted" to its dock, refusing to boot unless the dock is attached. The problem is infrequent (estimated to impact less than one percent of all Duo owners using docks), but when it happens, it can hit hard: the Duos often must be returned to Apple for repair. The Duo 210, 230, and 250 do not appear to be susceptible.
The problem is caused by transient charges moving from the dock to the Duo. These charges can damage an FET transistor in the Duo’s PDS connector circuitry: if the FET is damaged, the Duo fails to correctly detect the presence of a docking device, and when the Duo is booted without a dock, it thinks a defective dock is connected. The Duo then does exactly what it was designed to do in that situation: it refuses boot at all – no sad Mac codes, no sounds, no display – in an effort to prevent damage to the machine. However, when the Duo is booted with a dock attached, the Duo correctly detects its presence and boots normally.
Docking devices used for Ethernet connectivity appear to be the most susceptible to this problem due to wide variations in network architecture and hardware. Though most networks don’t cause problems, some may transfer a transient charge to a Duo when an Ethernet cable (10BASE-T) is plugged in.
Newer Technology – the largest third-party supplier of docking bars – noticed the "addiction" problems associated with the Duo 270c, 280, and 280c, and, working with Apple, determined that a protection circuit present in the earliest three Duo models was left out of the most recent three Duo models. Newer Technology now builds the missing motherboard charge protection circuitry into their docking devices to prevent transient-related problems from occurring.
Users whose Duos have been damaged should contact their Apple dealer about the problem (or contact Apple directly via 800/SOS-APPL) and let them know you are simultaneously contacting your dock vendor for an updated dock. Newer Technology offers a free exchange for affected customers. Remember that simply getting your Duo repaired by Apple doesn’t give you the missing charge protection circuitry; you’ll need to obtain a dock with the protection circuitry built-in to make sure the problem won’t recur.
It’s important to note that this problem impacts only a very small portion of Duo owners: paranoia is not justified. If you haven’t yet experienced the problem, the odds are very good you never will.
Newer Technology –800/678-3726 — 316/685-4904
316/685-9368 (fax) — <[email protected]>
John Vaudin <[email protected]>