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82-90xli Remote MCU Communication


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  • 82-90xli Remote MCU Communication

    I started at a new center recently and Ive got 10 82-90xli machines that are all running normally for the most part except when it comes to the Remote Manager Control Unit (picture below) located at the front desk.

    The MCU unit powers on and seems like it boots up without issue, but no matter which of the 4 RJ45 ports I try, I'm unable to communicate with any of the boxes in the back.

    Ive ran a fluke cable tester on the cat5 that goes from the remote mcu to the chassis on lanes 1&2 using a serial breakout adapter and it passes with no breaks found.

    Additionally, the 'remote' function on the chassis units in the back shoot out the same communication error when trying to access the mcu menu of another lair of lanes.

    The 9pin serial cables that go from one pair of lanes to the next, including the terminator pigtail on the final pair are hooked up and have been tested.

    I've exhausted all my low-voltage cabling and troubleshooting abilities at this point and look forward to having some more knowledgeable brains in the mix.

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  • #2
    First off, is the MCU connected to a Control Desk?

    The communications uses RS 485 so there isn't a lot to go wrong. Unfortunately, a problem in one device can kill the entire system. There will be an RS 485 driver chip in each chassis as well as in the MCU. If one of these goes bad it can drag down the entire network.

    To start I would check the machine address in the chassis. (probably ok but good to check)

    I would then limit the problem areas by removing most of them from the circuit. Disconnect the daisy chain at the output of the first chassis (the one connected to MCU). You will have to move the termination cable from the last chassis and plug it into the output of the first chassis.

    Then power things back up and see if you can communicate with just one chassis. If this doesn't work then move the MCU cable to the second chassis as well as the terminating cable to eliminate the possibility the problem was in the first chassis.

    Do you have a handheld unit and if so can this communicate with the units?

    Let us know what you find.


    • #3
      Thanks for the new info. Today was my last day off so I will be sure to try what you mentioned while im onsite tomorrow.

      We dont have a hand unit to my knowledge, but narrowing down the number of failure points like you mentioned should help me figure something out. I wasn't sure if I could remove parts of the daisy chain without reconfiguring lane chassis boxes. if it does seem like I have a failed rs-485 controller, is that a serviceable component or would a complete chassis replacement be required? I'm no stranger to a soldering iron and circuit repair if needed and we do have some out of service chassis units with unrelated issues that I could possibly pull from if thats a possibility.

      Thanks again, I'll be sure to check in with what I come across sometime in the next day or so.


      • #4
        How's the search going?

        You shouldn't need to reconfigure anything. If in doubt, just leave the others off while you test the one. RS 485 is a master slave network electrical specification (not a protocol). The protocol would be established by big "Q" but that doesn't effect the underlying physical network. Think of it like a train mainline that goes from start to the end. You then add side lines to service individual stops or in this case chassis. Even if an individual station is offline, the mainline still goes through so nothing is disrupted. Each station has a unique address. When a message is sent, they all look at the message and if it has their address, they read it and respond to it. If it's not addressed to them, they simply ignore it. In your case you are just ending the mainline at the first station so it will respond to messages addressed to it an ignore all others. Even if you left, for example, only the sixth chassis as the only chassis online, it would still work as long as the message sent was addressed to it's address. No need to reconfigure it to number one. Just send the message to the 6th machine pair and it should work.

        Internally, in the chassis, there is a connection that maintains the main line. So if you remove an individual chassis, you break the main line and so any chassis after that point would no longer get the message. The chassis before that break may or may not still work. If you didn't have a chassis to put back in to re-establish the mainline, you could use a splice connector to bypass the chassis and re-establish the mainline. The terminating resistor needs to be at the end of the mainline. Some networks will work without it. There are certain things that will determine whether a network will work without a terminating resistor such as cable length and baud rate but to be safe, try to always include it which is why I had you move it to the first chassis during this test. So by terminating the mainline at the first chassis, it will simply ignore messages not addressed to it even if they are sent. Of course, none of the machines past the termination point will get the messages either but this should be ok during testing.

        I'm not sure how serviceable these are one these chassis. If it's the driver then it's just a chip that needs replaced. Many times they are socket mounted so you can just pop the old one out and put a new chip in. Other times they are soldered in but shouldn't be a hard fix. The part should be readily available for a couple dollars. You can post some pics of the board and we can help you isolate it.

        Keep us informed. Sorry for my delayed response.


        • #5
          Sorry for the radio silence. Been a trying week...

          The handheld unit was found, unfortunately, and since nobody currently working here is aware of the history of a lot of things due to a few turnovers in ownership it smoked the chassis of the first pair of lanes it was plugged into. Turns out the handheld itself is either shorted out bigtime or cursed.

          So now I'm down 1 pair with no spare, trying to find a replacement 82-90xli chassis or even just a logic board replacement. After that ordeal, i havent had a chance to try and suss out the front desk unit. Anyone have a reccomendation on where to buy a new chassis or to get repaired? QAMF doesnt seem to have any, and the cheapest I found was $1900 but 2-3 weeks away in china via Alibaba.


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