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Thread: Thermaltake Xaser III - 1394 Socket is WIRED WRONG




  1. #1
    Join Date
    Jun 2003
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    1

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    Visit http://www.meltybrain.org/1394 for more information about this wiring defect, including detailed pictures and full references to the IEEE 1394 specification.

    Here's what happened:

    On March 22, my wife and I both purchased new Thermaltake xaser III cases for our new Asus A7N8X mainboards from FunKey Computers in Bellevue, Washington. We finished building these systems about 1 week later but hadn't had a chance to fully utilize all of the features on the case (including the top 1394 socket) until the evening of April 16, 2003.

    My wife attached her Creative Nomad Jukebox III to the top 1394 socket using a 6-Pin to 4-Pin 1394 cable and it wouldn't enumerate. I then tried to use my xaser IIIís 1394 socket as well, and it also didn't work. I tried to use one of my 1394 portable hard drives -- It never powered up. We turned off both of our machines and each attempted to locate the problem, because we were both completely certain we connected the case and connector wires correctly. We verified that the 1394 socket VP, VG, TPA+/-, and TPB+/- pins were connected to the correct pins on the mainboard per the owner's manuals for both the case and the motherboard. We turned on our machines and continued to troubleshoot the problem. After a while, I decided to test my portable 1394 hard drive in another computer. The drive would not energize (it's powered by the 1394 bus) and would not operate and appeared to be completely dead. I then started to suspect a 1394 power problem, but the other port off the mainboard was working fine (the A7N8X board has 2 1394 ports).

    At this point, we identified the 1394 chip on our A7N8X mainboards (Realtek RTL8801), and physically examined the chip on my wife's machine. It was too hot to touch. I then immediately shut off power to both of our machines and started looking for a short on the 1394 bus. Once again, we verified that we had the connectors properly connected to the mainboard. I disconnected all 1394 devices on my system and re-energized my system.

    Using the pinout information located in the IEEE 1394-1995 specification, I found a MAJOR wiring problem on the top 1394 socket on both of our cases. The VG (Ground) and VP (Positive) pins are reversed. The mainboard VG wire (Ground) connects to pin 1 of the top 1394 socket, which SHOULD be connected to pin 2. The mainboard VP wire (+12v) connects to pin 2, which should be connected to pin 1. All other TP data pins are correct. As a final test, I plugged the cable back into the mainboard per the pinouts in the A7N8X motherboard manual, and used a multimeter to measure voltages on the pins. I measured 12V+ on pin 2 of the top firewire connector.

    Some people might wonder why my wifeís Creative Nomad Jukebox III, which uses a 4-pin 1394 cable, was damaged by this problem. As you may know, 4-pin 1394 cables do not provide bus power to the connected device, however, If you actually use a multimeter to measure continuity between the 6-pin plug and the 4-pin plug of a 1394 cable, youíll see that the outer metal shield of the 6-pin plug is NOT connected to the outer metal shield of the 4-pin plug. Instead, pin 2 of the 6-pin plug (GND) is actually connected to the 4-pin plug outer metal shield. That means that when you use this kind of cable with the xaser III 1394 socket, youíre actually connecting POSITIVE 1394 bus power voltage to the shield of the 4-pin connector, not GROUND, which directly shorts out the controller chip. Cable shields are normally assumed to all be common, and if the xaser IIIís 1394 socket was properly wired, it would be. Imagine the potential damage you could do to your car if you installed your battery backwards and that should give you some idea of whatís happening in this situation. While fuses can protect electronic circuits from over-current situations, they donít protect a circuit from reverse-polarity Ė thatís what diodeís are for. Unfortunately, most PC peripherals donít incorporate circuit protection measures to guard against the possibility of reverse polarity, because they assume that the manufacturers who create these devices all follow the same specification and actually test their devices before delivering them to their customers. Thermaltake obviously didnít test the xaser IIIís 1394 socket using a bus-powered device or they would have seen this problem.

    I've created a web site that specifically addresses this problem - please visit http://www.meltybrain.org/1394 for more information.

    If you've seen this problem OR been affected by it, PLEASE let me know!

    Thanks,

    Sonartech

  2. #2
    Join Date
    Nov 2001
    Location
    New England Highlands, Australia
    Posts
    21,907

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    Thanx for the the info m8.

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