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Found 3 results

  1. Hello Recently I got a macintosh classic that have the checkerboard screen issue. When I opened the machine, I saw a huge corrosion mark under the analog board. I thought it would be some leaking capacitors like many macintosh of this model have, I was ready to recap boards. But it's not. Actually no capacitors have leaked, it's the PRAM battery that opened up completely (litteraly). The analog board seems to be fine but the mainboard has been corroded so much that the battery holder has desoldered. I've tried to clean up some of the corrosion with isopropyl alcohol but there's still a lot of this brown heap. I'm now looking for help on how bring that board back to normal running; like get rid of the corrosion and maybe rewire some pcb tracks and put an PRAM equivalent battery. The machine powers up fine to the checkerboard screen, I tested it before opened it. Here's pictures of the disaster: The leak corroded the chassis. Where the leak occured, the battery holder was where the corrosion heap is. It affected some of chips legs and resistors on the other side. The dead battery. The top is slightly open. The battery and its holder. The holder is completly ruined and was desoldered by the corrosion. Hoping that you can get me some help
  2. dochilli

    Mac 512 Mainboard repair

    Hello! I bought a Mac 512 that has a problem with the mainboard. When I got the Mac, the ROM chips (low, high) were interchanged and the MAC did not start. I changed the ROM chips and the the MAC started somtimes. Sometimes I got a sad MAC with the error 05FFFF. Sometimes I got no Image and sometime the MAC started up to the disk picture. At every start I do not get a chime. When I put in a disk the picture begins to wooble and then the MAC crashes, sometime there can be heard some sounds. I can not read a disk without crashing. What I did up to now: - Changed the ROM against a ROM from as Plus => mainboard did not start (I tried this only one time, so I do not know if the mac would start, when I try it more often) - Changed the whole mainboard against a Plus mainboard => computer starts (analog board seems to be ok). - Controlled the voltages: +5, +12 and -12 are ok! - resoldered the mainboard connector from the analog board - changed the electrolytic capacitors. One of the capacitors (33mF, C5) could not be measured when it is soldered. Before soldering it shows 33mF after soldering it was not possible to measure. The other two could be measured when they were soldered. The polarity of all capacitors is correct. I do not have another diskdrive, so I could not test, if the drive is the problem, but I think there must be a problem on the mainboard. There is no chime, starting did not work every time (sometimes no picture, sometime sad mac, sometimes "disk mac"). If I do not connect the disk drive the problem occurs too. When I opened the Mac I saw that that the shield of the mainboard (metal sheet under the mainboard) had no paper card on the mainboard side, there was no isolation! So I think that there could been a short on the mainboard caused by the shield. Ok, I hope you can understand, what I wrote. I am from Germany... Has anybody an idea what I can do to repair the mainboard? It would be very nice to see this machine working again. Greetings Martin
  3. ArmorAlley

    Recapping - Current thinking

    Hello everybody, What is the current thinking in regards to recapping boards with orginal caps that work? I^m thinking particularly of the SE, SE/30 and Colour Classic. For the latter two, something is not working, the SE works. My initial thinking was that these machines are over 20 years old and will need new capacitors anyway. Some posters have commented, especially for the SE, that if it is not broken, do not fix it. Is preventative action wise? unnecessary? My second question concerns what should be recapped? I was initially thinking of just getting the mainboard recapped. Again, from reading through posts as well as in general online, it seems that one should get both the PSU and the analog board done as well. Is this also wise and or unnecessary? Getting the machines recapped is pricey (I really do not like soldering), but if I can get give these machines another 25-plus years of service, it will be worthwhile, well, until the CRT finally packs it in and I have to replace it with some wonder-LCD replacement. I am interested to hear your opinions, aa