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LEJ-640FT Fuse - Troubleshooting

Discussion in 'Roland' started by sajego, Oct 14, 2020.

  1. sajego

    sajego Since 2010

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    Dec 8, 2019
    Reno, NV
    A few weeks ago my magenta stopped printing in the middle of a large job that really needed magenta. I troubleshooted the ink system parts and got it partly working again, and then it was gone completely along with the Cyan. Turns out the F1 fuse was blown. My tech (unofficially) said try unplugging the ribbon cables between the print head and carriage board to see which print head was the problem. Either both are or neither are, the fuse blows any time I turn the printer's subpower on.

    To me, this doesn't sound like something that can be solved by replacing print heads, and I'm worried the new print heads will be damaged.

    What's the next step? I'm happy to have a tech look at it but I don't have a local tech since I moved to the Reno area from Virginia and the local salespeople don't want to support my machines since they didn't sell them to me.
     
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  2. Solventinkjet

    Solventinkjet DIY Printer Fixing Guide

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    Aug 2, 2011
    Denver, CO
    I had a similar issue with an XC-540 printer recently which uses a similar head board. It ended up being a bad head board. If it blows no matter which head is plugged in, it could be a bad trailing cable or even a damaged/dirty slider board but my bet would be on the head board. I'm not a Roland expert though. Maybe Jim HancockJim Hancock has another idea.
     
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  3. sajego

    sajego Since 2010

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    Dec 8, 2019
    Reno, NV
    It blows with whichever head is plugged in or with no heads plugged in which isn't normal behavior (I checked using a different fuse group).

    ((I'm struggling to keep the boards straight, the head board you mention is attached to the print head and there's one for each print head? Or is it the board I'm thinking of as carriage board where the ribbons go from each head? Or is it the board where the fuses themselves are?))
    Answering my own question: the one where the fuses are.

    Thanks for the reply. Sometimes I wish I wasn't an engineer so I could just pay someone to do all this without feeling like I should be able to do it myself. :)

    Sara
     
    Last edited: Oct 14, 2020
  4. Solventinkjet

    Solventinkjet DIY Printer Fixing Guide

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    Aug 2, 2011
    Denver, CO
    It's the board with the fuses on it. That's where the signal gets amplified and my theory is that one of the transistors goes bad and pops the fuse. If you know how to test transistors, you might be able to fix the board rather than replacing it. Unfortunately my electronic skills end at testing fuses!
     
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  5. sajego

    sajego Since 2010

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    Dec 8, 2019
    Reno, NV
    Same. Mechanical engineer, not EE. I also read in another thread that the transistors are paired and replacing just one can cause issues too. So where's the best, fastest place to get a head board from?
     
  6. Solventinkjet

    Solventinkjet DIY Printer Fixing Guide

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    Aug 2, 2011
    Denver, CO
    Try Ordway Sign Supplies in Van Nuys, CA. They should be able to help.
     
  7. Jim Hancock

    Jim Hancock Active Member

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    Delray Beach, Florida
    You should check the output transistors on the headboard. They are the transistors mounted to the big heatsinks. Read the outer 2 legs of each transistor, they should read around 42 ohms. They are marked as C4131 & A1746. Most likely you are going to find one or more are shorted and this will continue to blow fuses until they are replaced. If you do not have anyone to do this, I offer it as a service.
     
  8. netsol

    netsol Very Active Member

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    Apr 26, 2016
    englishtown, nj
    am pretty sure that NTE, TCG &ECG (if they still exist) make replacements

    original or aftermarket, always change in a pair

    use heat sink compound (the goo behind the heatsink the transistor screws to)
     
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