Dell Axim X50(v)/ X51(v) cradles: are they indeed lethal?!

In the microsoft.public.pocketpc newsgroup, I’ve promised to look into the problem of the Dell Axim X50(v)/ X51(v) cradles frying up motherboards you can read more of here (a highly recommended thread – you may want to read at least the first post in there. Note that there are a lot of posts in there that are uncertain; therefore, it’s better to read my article first. In here, I tried to clean up and summarize everything worth knowing.). Note that there are two other, but older and less specific threads discussing the same question here and here. Note that there is another sticky AximSite thread here on a similar matter. It, however, only discusses third-party sync/charge cables and NOT the standard cradle coming with the PDA. Therefore, I only recommend the last thread if you’d like to purchase a third-party cable. If you don't, you won't need to read it.

First, all the (to my knowledge - if you have a newer cradle revision, let me know) three cradle revisions (the initial A00, A01, which started to ship around December 2004 and A02, which started to ship in July/August 2005) seem to have this problem – again, even the last (and, to my knowledge, still current) A02. (As far as the latest, A02 revision is concerned, see d00567’s posts on 09-25-05 and 09-26-05 here).

Dell states it’s a manufacturing defect. It’s pretty sad to see their quality control does not check for this problem.

Note that the cradle cable only recharges the PDA (if no AC adapter is plugged in) while the PDA is off (this itself means the USB host will not need to power the PDA itself, only the battery), I don’t think it’s a “PDA overloading the desktop with larger than 500 mA†(the maximal USB charge Amperage USB ports should be obligatorily certified) case; not when the PDA is plugged in (as opposed to, say, the Pocket Loox 720, the iPAQ hx4700 or any HTC PPC Phone Edition device that has a mini USB sync port). You, however, may encounter problems because of this, particularly if you try to charge a severely depleted battery off USB (with depleted batteries, the charging current may be well over even 1 Ampers (see for example these figures), which is way more than a USB host may be able to provide). Then, the USB port in the desktop computer may indeed be overloaded. The “burn out†cases, however, show the problem is lying somewhere else.

If you still don’t want to put any strain on your desktop computer, USB recharging-wise, make sure you only connect your PDA to it when it’s not switched off (if you don’t have an AC adapter around – if you do have, always use it instead in the way I’ve explained at the end of the article) so that USB charging doesn’t “kick inâ€.

My tests

I’ve tried really hard to lock up my computer (which the cradle is directly attached to; the USB2 ports are on the motherboard) by removing and replacing the PDA in the AC- and USB-connected cradle (A02 cradle revision – it’s an x51v, which were, as it seems, all delivered with A02 cradles) like mad. I’ve done the same with a cradle not AC-connected to see whether anything happens. Nothing happened.

I’ve encountered some kind of static (and a resulting voltage difference between the PDA’s USB cable and that of the computer) on the cable before the first connection (after switching on the desktop PC), but it’s a problem with the USB port itself, not the PDA and, therefore, affects all Pocket PC’s, not just the Dells. After the static has been shorted out (it has never caused me any problems so you shouldn’t be afraid of it either), I’ve done some serious measurements to see whether there is any voltage leakage or potential difference between the chassis and the PDA’s ground. I couldn’t find any.

That is, my particular setup worked OK (both in my tests and in the last 8-9 months). This, however, may mean I’m plain lucky not to have a defective unit.

Still, how can you be ABSOLUTELY sure you won’t ever damage your desktop PC?

If you are afraid of frying your motherboard (or the USB circuitry), always do the same, in this order:

1. plug in the AC charger in the cradle
2. put the Axim onto the cradle
3. connect & disconnect USB cradle to/from PC as desired.

This all means you should only put the Axim on / take it off the cradle only when the cradle has AC power but is not connected to the desktop PC via USB. That is, do not connect the Axim to the PC unless the Axim is in its cradle, receiving AC power.

You may also want to consider using self-powered USB hubs. Public opinion certainly differs on them; they may prove useful with your particular setup.

Alternatively, if Bluetooth’s nearly-an-order-of-magnitude less speed isn’t a problem, do all your ActiveSync synchronization via Bluetooth (or, with WM2003SE x50(v)’s, Wi-Fi) and never connect the cradle to the desktop computer. Then, you will be absolutely safe.

UPDATE (later the same day):

Two additional thoughts: whether it's "just" the recharge current that is causing the problem and how external/additional USB cards / surge protectors may help.

1. one of the AximSite posters stated his ThinkPad completely shut down once upon cradling the Axim. The IBM ThinkPad completely shutting down (needing the removal of the battery for some seconds in order to get it back into life) clearly shows there was a short circuit - not just a plain "too much energy is needed" situation. I too own a IBM ThinkPad and had exactly the same situation with a badly constructed external HDD enclosure one day (the power cable of the enclosure is engineered in a very bad way, very easily causing short circuit). It's only at direct short circuits (and NOT "only" excess Amperage needs) that the ThinkPad shuts down in a way that requires the battery to be (temporarily) removed.
2. if you are afraid of burning / frying your motherboard but wouldn't want to switch to the slow Bluetooth / don't want to take risk, a very cheap alternative is just getting a USB2 PCI card if it’s a desktop computer. If, on the other hand, you have a notebook, you may want to invest into USB-capable power surge / short-circuit protectors OR externally (self)-powered USB hosts instead; these, BTW, should also work with the desktop too (just remember NOT to do any ROM upgrading through them!). Another alternative is using PCMCIA USB(2) cards with your notebook. I’m not sure whether the latter will protect the notebook’s motherboard (a very expensive item – much more expensive than desktop motherboards) though. Then, if the cradle does cause a short-circuit, it’s only the USB card that dies (and the surge protector, naturally, defends your PC), not the in cases order(s) of magnitude more expensive motherboard.

   You can safely use additional PCI (or, for that matter, PCMCIA) USB(2) cards in a desktop (notebook) computer; they won’t interfere in the built-in USB(2) ports. Actually, I’ve actively been using one of these cheap cards in my desktop computer and never had any problem with it, except for a blue screen of death once, upon trying to update my HTC Wizard, connected to the PCI USB2 card, to the latest 2.26 ROM version. I haven’t had such cases with the built-in USB2 ports (have done dozens of ROM flashes on it, particularly when flashing different ROM versions to my Wizard in rapid succession to find out their differences, boot-in and EDGE speed). That is, try avoid doing any critical – for example, ROM update – using a PCI add-on card; then, just (temporarily) switch to using the built-in ports and just make sure you cradle your Axim and put in the wall charger before connecting the cradle to the desktop computer.

UPDATE (09/10/2006): PPCT frontpage; worth reading for some other user reports

UPDATE (03/18/2007):: MobilitySite frontpage