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?Circuit board? Help/fix

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  • ?Circuit board? Help/fix



    The part that is circled is the path to the start button on my printer. Is there a way to fix it?

    I am pretty sure thats where the break is as my start button dont work on my printer

    I guess you can call it a circuit board, but its thin and flexable

    I wouldnt mind buying a new circuit board, but cant seem to find one. Its for a Brother MFC 8440

  • #2
    There is a kit to repair broken traces for automotive window defrosters. Scrape gently to expose the copper traces and apply the repair goo, or a small bit of solder carefully applied to join the broken traces. I have repaired many similar items using either method.

    Ed

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    • #3
      What makes you so sure that area is to blame.
      Unless you can see a break in the tracking I would suspect the fault lies elsewhere.
      The circuit is similar to keyboards in that there are 3 layers folded onto themselves and the buttons just bridge a gap and make a circuit very low power.
      Only bad one ive seen is when some orange juice got spilt onto a remote when opened all the tracks in an area had disappeared.
      Peter
      I have tools I don't know how to use!!

      Comment


      • #4
        Originally posted by ptjw7uk
        What makes you so sure that area is to blame.
        Unless you can see a break in the tracking I would suspect the fault lies elsewhere.
        The circuit is similar to keyboards in that there are 3 layers folded onto themselves and the buttons just bridge a gap and make a circuit very low power.
        Only bad one ive seen is when some orange juice got spilt onto a remote when opened all the tracks in an area had disappeared.
        Peter

        Well, the facts that the board is damaged and the start button doesnt work would be my leading indicators that its the problem.

        As for layers, I dont see any other leads or wire paths

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        • #5
          If there are no layers is the copper side underneath in the picture.
          So if the track is broken then it can be repaired using silver rear screen paint which should work as ecortech says
          Peter
          I have tools I don't know how to use!!

          Comment


          • #6
            upon a deeper look under magnification, yes, there is a break in the paths.

            I am attempting to scratch down to it now with tweezers

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            • #7
              Use some fine sand paper and sand down through the conformal coating (Varnish.) until you get to copper. Put a dab of flux on the exposed traces and take the solering iron and tin the traces. sometimes you can bridge the breaks with the solder. If not take one strand out of a piece of stranded wire and tin that. Use the wire to span the break.

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              • #8
                those floppy circuit boards (membrane switches) can be a tough fix because of heat you'll need to put down with an iron (if you go the hot-solder route).

                not to sound smart.. but how about putting a staple through it?

                i've got a real small stapler here that lays down 1/8" wide, almost round wire-style staples. a regular staple might be wide enough to cut the path again.. can't really tell what scale i'm looking at.

                probably a dumb idea -- i'm more of a mechanic than an electronics guy.. but there you have it.

                -Tony

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                • #9
                  What Macona said. I would use an xacto knife or similar, and scrape the trace both sides of the break until the copper shows and no streaks of color remain. With a decent resin core solder, tin the traces. Don't make the mistake of using acid flux, as meant for plumbing with copper tubing. Use a strand or two as suggested, and bend into a u shape with flat bottom. This part of the wire is pressed onto the junction with a soldering tip, then what remains can be cut off. This way you have something to hold onto while positioning the strand. If you can't get a side cutter in there to remove the excess strands, you can always flex them until they break away.

                  What works quite well when soldering is to wet the part of the strand that's going to be used with the solder, then wick away the excess with the soldering tip. Clean the tip on a wet sponge and the strand will then easily blend with the tinned traces without you having to add more solder. Too much solder is bad. Usually a good join looks to the unfamiliar like it doesn't have enough solder.

                  I wouldn't rely on just a solder bridge, since the board is cracked there (I'm assuming).
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                  • #10
                    Don't try the staple: you will never get a reliable connection. What Darryl said sounds good but be careful not to use too much heat or the board will self destruct. Do use a low wattage iron, 25 or 35 Watts maximum. I would tin the wire strand and put some flux on the exposed copper trace. Then put a small drop of solder on the iron and just wipe it across the bare trace to tin it. About one second should be the longest time the solder puddle on the iron contacts the trace. It should tin easily if it is clean. Then apply the wire using the same technique: a small drop of solder on the iron and a quick swipe over the wire on the trace. Do the other side of the break and then cut off the excess wire.
                    Paul A.
                    SE Texas

                    Make it fit.
                    You can't win and there IS a penalty for trying!

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                    • #11
                      You would want a soldering iron with an adjustable temp
                      knob turned as low as it will go and still melt solder and a
                      needle point tip at most 1/32" to minimize heat
                      to the plastic. The plastic underlay is so thin it would be
                      easy to burn a hole. Window defrost repair kit is a better
                      idea, less likely to do irreparable damage.
                      Steve

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                      • #12
                        I like the window heater repair paint too.

                        Anyone ever make scribbled circuits? You can make RC arrays on regular writing paper with a soft lead pencil and clip to it. Capacitors are made by scribbling areas on both sides of the paper. When done paint with nail varnish to stabilize, or don't and use it as a humidity sensor.

                        A while back it was possible to jumper some of the Athlon processors with a pencil scribble to unlock the CPU multiplier. It's even possible that the trick would work here.
                        Free software for calculating bolt circles and similar: Click Here

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                        • #13
                          That reminds me... There are circuit board repair pens available. They have a silver compound in the pen. Where ever yu draw it leaves a path of metallic silver. It can even be soldered to I think. There is a overcoat pen that you apply after to protect the trace.

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                          • #14
                            You need to go with solder for the mechanical strength. Because it's a control panel, it normally experiences a lot of flexing thru use. I would assume that there is something contacting the board at the point of failure which caused the problem to begin with. Silver ink won't hold up well in this situation. I've repaired hundreds of traces using solder both with and without a bridge wire depending on circumstances. Even under mechanical stress, I've never had a soldered repair fail. Silver ink works well on silk screened mylar circuits and ribbon cables, rear window defrosters, and conventional copper clad boards provided the joint experiences no mechanical stress. Darryl provided an excellent description of the process.
                            The early bird may get the worm but the second mouse gets the cheese.

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                            • #15
                              Can't tell for sure from the pic, but that looks more like an intentionaly cut track rather than a break. Sometimes manufacturers will do that to either fix a mistake or calibrate a circuit. A broken track will not have a gap to it whereas if intentional it will look like it has been hit by a saw or dremmel tool.

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