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Recent content by CygnusTM

  1. CygnusTM

    IIsi powers on and off on its own

    The switch is now the prime suspect. I didn't have time to take it apart and investigate the switch, but I did have time to start it up and lock the switch in "server" position. It ran all day without spontaneously shutting off. When I get a chance I'm going to see if I can get some DeoxIT in...
  2. CygnusTM

    IIsi powers on and off on its own

    Yes, I did, and it has a Sony power supply. I guess I should focus my investigation there?
  3. CygnusTM

    IIsi powers on and off on its own

    Since buying this IIsi, I replaced the PRAM battery, upgraded the RAM (from 5MB to 17 MB) and recapped the PS and the system board. Before and after these modifications, it will randomly power itself on if left plugged in, and it will randomly power itself off while trying to use it. Sometimes...
  4. CygnusTM

    IIsi RAM Upgrade

    So after examining the SIMMs more closely and searching part numbers on the PCB, I found that these aren't the Samsung parts stated in the listing. They are actually Siemens parts that I can't find much info on. So they are getting returned. I bought another set that specifically says they work...
  5. CygnusTM

    IIsi RAM Upgrade

    Yeah, that was one of the pages I used when I was researching. These are FPM chips with better than 100 ns speed, so I thought they would work. I did find one page (https://oldcrap.org/2018/11/25/macintosh-iisi/) that seems to show a IIsi with 3-chip SIMMs.
  6. CygnusTM

    IIsi RAM Upgrade

    I recently picked up a IIsi. It came with 5MB of RAM (4 1MB SIMMs installed), and I am trying to upgrade to 17MB. I picked up 4 4MB SIMMs on eBay (https://www.ebay.com/itm/224577279767), and the IIsi won't see the SIMMs at all. I've tried reseating it and a PRAM reset. How picky is the IIsi...
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