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Apple iie Platinum Garbled Screen Part 2

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    Apple iie Platinum Garbled Screen Part 2

    This is a continuation of a previous post on the same issue. Here is the first post: http://www.vcfed.org/forum/showthrea...Garbled-Screen

    I have now installed new ram, it did help a little but it is still not functioning correctly.1.jpg2.jpg3.jpg4.jpg5.jpg5.jpg6.jpg

    #2
    Im definitely not too familiar with the Apple II line, in fact I have an II+ that I will need help on getting to post. But this seems to be an issue with the Character Rom. I havent read the previous posting, but was the character ROM checked?

    Comment


      #3
      The character ROM is fine, the characters are wrong but are displayed perfectly.

      Its clear that the CPU is getting bad instructions, since RAM has been ruled out. There are some other candidates that can cause that issue.
      Check the +5v on the motherboard it should be between 5v and 5.25v but definitely not below 5v. Also check for AC ripple on the 5v line.
      If the power looks good check/replace the sockets on the board, in your first post you mention some signs of corrosion on some of the chips.

      I still think you should try the diag eprom I sent a link to, the results you get will narrow down the problem.

      Comment


        #4
        I measured the voltages, +5v is at 5.1v but +12v measures only 11.13v. The only other thing is, I'm not quite sure how to measure for ac ripple. Sorry.

        Comment


          #5
          To me, this just screams corrosion somewhere. I'd pull all the chips one by one, check for green fuzzies, and reinsert. I'd even go so far as to send the board through the dishwasher for good measure.

          Did you check the power supply UNDER LOAD? It makes a difference with these units I've noticed.
          It is a mistake to think you can solve any major problems just with potatoes.

          Comment


            #6
            Originally posted by masterpigeon View Post
            I measured the voltages, +5v is at 5.1v but +12v measures only 11.13v. The only other thing is, I'm not quite sure how to measure for ac ripple. Sorry.
            To measure for AC ripple with a digital multimeter just set the meter to the AC range and it will filter out the DC component.
            11.13v is fine if there is no AC ripple on it, was the power supply under load at the time?

            Comment


              #7
              I checked the voltages on the board once more, 12v measures 11.53v and 5v is still 5v. I don't believe there is any ac ripple with either of them. (It measured 0.004acv)

              Comment


                #8
                Here is a picture of what the computer was doing after I reseated all the chips. it won't do anything else now, It only displays this screen. I also noticed something missing on the board while cleaning it.IMG_20180124_132105.jpgIMG_20180124_132503.jpg

                Comment


                  #9
                  Holy crap that pitting!
                  How much corrosion is going on all over that board?

                  Also CR2 is where an LED would normally sit. It is missing on your machine.
                  [Need something to waste time on? Click here to visit my YouTube channel CelGenStudios]
                  --------------------------------------------------------------------------------------------
                  [No time for videos? Click here to visit my Twitter feed @CelGenStudios]

                  = Excellent space heater

                  Comment


                    #10
                    wow, just wow.

                    That's a corrosion problem.
                    It is a mistake to think you can solve any major problems just with potatoes.

                    Comment


                      #11
                      Here are some pictures of the board:

                      IMG_20180124_141049.jpgIMG_20180124_141056.jpgIMG_20180124_141102.jpgIMG_20180124_141110.jpg

                      Apparently, the guy I got it from stored it in a leaky shed for several years and it must have gotten soaked because when I first picked it up, heaps of rust fell out. My table is still covered in it. Most of the metal base was rusted and heavily pitted but the board sort of looked ok but apperantly not. So that is why the board looks the way it does.

                      Comment


                        #12
                        well... There isn't much to lose at this point.

                        Get some dish soap, a brush with long stiff bristles, and some super hot water. Go nuts. Hopefully it helps. I personally use Dawn soap.
                        It is a mistake to think you can solve any major problems just with potatoes.

                        Comment


                          #13
                          The board has been washed! Now it's drying...

                          Comment


                            #14
                            Well, soaking it didn't break it... nor did it fix it. It just changed it slightly.

                            IMG_20180124_163604.jpgIMG_20180124_163621.jpgIMG_20180124_164606.jpg
                            It will display the bars or thin bars and eventually change to the '@' screen.

                            Comment


                              #15
                              Well, I would have let that dried longer... In all likelihood there is a broken (or shorted) connection somewhere. Or a bad chip maybe. You might try over at http://www.applefritter.com/ they are more specialized on these systems.
                              It is a mistake to think you can solve any major problems just with potatoes.

                              Comment

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