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Mac 128k - J1 Yoke connector problems

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    Mac 128k - J1 Yoke connector problems

    So I got bone stock Mac 128k which was suffering from the apparent common problem of the screen not turning on, but slapping the right side of the case causes it to jitter on for a moment. I reflowed the solder on that connector as most guides I've found instruct. However, that did not solve the problem. With the case open and power on, I carefully wiggled the J1 yoke connector cable and it started working. So I think the problem is with the wiring harness/connector itself. Has anyone seen or repaired this? I'd prefer not to have to solder the wires directly to the analog board if a better option exists?

    #2
    if slapping it makes it come on try resoldering the pins on the flyback. ITs heavy and in a under normal conditions causes strain on the analog board. Check for any small cracks around the flyback as well.

    The problem you describe I have seen before and a cracked pcb or bad solder joints on the flyback have been a culprit many times.

    If you are convinced its the yoke do a resistance check on the horizontal and vertical windings. When taking the measurements wiggle the cables alot (looking for a break in the wire)

    Comment


      #3
      Originally posted by VERAULT View Post
      if slapping it makes it come on try resoldering the pins on the flyback. ITs heavy and in a under normal conditions causes strain on the analog board. Check for any small cracks around the flyback as well.

      The problem you describe I have seen before and a cracked pcb or bad solder joints on the flyback have been a culprit many times.

      If you are convinced its the yoke do a resistance check on the horizontal and vertical windings. When taking the measurements wiggle the cables alot (looking for a break in the wire)
      I had already also resoldered the flyback as well as all the other wire harness connectors - so that's not the problem. I don't think it's the connections at the yoke itself, I think its the plastic connector where it connects to the analog board. Circled below... the connection itself feels loose and wiggles a lot.

      20211011_171812.jpg

      Comment


        #4
        well if you suspect that is it, that easy. thats just a pin and tube style connector.. using very thing needle nose pliers you can "slightly crimp" the tubes so they make a tighter connection. use some deoxit as there may be some tarnish inside.

        Comment


          #5
          Originally posted by VERAULT View Post
          well if you suspect that is it, that easy. thats just a pin and tube style connector.. using very thing needle nose pliers you can "slightly crimp" the tubes so they make a tighter connection. use some deoxit as there may be some tarnish inside.
          Ooh lol that seems so simple... I'll give that a try.

          Comment


            #6
            So, that's better but I don't think it's permanent.. it comes on and stays on now but if I jiggle the cable it'll flicker off.. I'm afraid by the time I get the case put back together it'll stop working again.

            EDIT... ok, some more playing around, now I'm not so convinced it was that connector afterall.. If I flex the PCB just the slightest amount, it does the same thing.. I think I'll spend some time resoldering the whole board....

            EDIT 2... Well I just went through & resoldered every point on the analog board.. it turns on just fine but when I flex pcb slightly the picture goes out.. so weird.. i think i'll button it back up and see how long it lasts...
            Last edited by nullvalue; October 11, 2021, 05:46 PM.

            Comment


              #7
              you have a crack.. a cracked trace or a cracked component or fraying wire. Have a magnifying glass? Inspect both sides of the board. Look for the halo of a cracked solder joint or anything I mentioned above. Wiggle the component or connector and look on both sides of the board.
              Last edited by VERAULT; October 12, 2021, 03:22 AM.

              Comment


                #8
                Ok I'll go through the whole thing very carefully... Will report back what I find

                Comment


                  #9
                  I would recommend just redoing every joint on the analog and neck board. All of the joints on the analog board are subject to microscopic cracks from the years of heat and decades of oxidation. Sometimes they'll get bigger and appear as a second ring within the ring of the solder joint.

                  Another issue are the potentiometers oxidizing and making poor connections. You can mark their position with a sharpie and flood them with contact cleaner or deoxit gold and wipe them back and forth several times until black oxidized crap stops coming out of them. I've had potentiometers going bad cause the screen to act wonky a few times.

                  Comment


                    #10
                    Well I went over everything, couldn't find any broken traces or any bad looking components. I did clean up the pots with some deoxit...put it back together and just my luck: no picture at all now. Can't even jiggle anything to get it back.. The annoying thing is I know the digital board is working well - even booted into Finder/System 2.0 from floppy

                    Comment


                      #11
                      So besides looking st it did you resolder snything or make changes. this type of task i would just hit all the problem spots with a fresh dot of solder with the iron.

                      Comment


                        #12
                        Originally posted by VERAULT View Post
                        So besides looking st it did you resolder snything or make changes. this type of task i would just hit all the problem spots with a fresh dot of solder with the iron.
                        Yep I resoldered literally every point on on the back of the analog board. I'll go through it all one more time I guess.

                        Comment


                          #13
                          Ok so I went through carefully and made sure I hit every solder point, wiggled the legs gently as I touched them up. Plugged it all back in and it's working now... Seems I must have got it this time around, the video doesn't cut out when I wiggle the board/cables around.. Thanks guys. Now I just need a keyboard & mouse since this model predates ADB... if anyone has one for sale, hit me up. Looking for an original M0110 keyboard and M0100 mouse.

                          Comment


                            #14
                            Those are starting to get absurdly pricey. They do make an adapter that will let you use a standard mouse in place of the m0100 but I dont think there is a modern adapter for the keyboard yet. Keep in mind there are burnt out Keyboards out there from people plugging standard phone lines into and short out the KB pcb. I have a couple I harvest switches from.

                            Just curious when you were hitting up the solder points were you adding a touch of new solder as well?

                            Comment


                              #15
                              Originally posted by VERAULT View Post
                              Those are starting to get absurdly pricey. They do make an adapter that will let you use a standard mouse in place of the m0100 but I dont think there is a modern adapter for the keyboard yet. Keep in mind there are burnt out Keyboards out there from people plugging standard phone lines into and short out the KB pcb. I have a couple I harvest switches from.

                              Just curious when you were hitting up the solder points were you adding a touch of new solder as well?
                              Yeah they are pretty ridiculous so I'll just be watching eBay like a hawk (saved search) - hopefully a good deal comes along. Good to know about burnt out ones - too bad there's probably no way to test them ahead of time..

                              Yes I did add fresh solder to all those points.

                              Comment

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