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Big Ben

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  1. Hi and happy new year /o/ So I had this LC III motherboard sitting alone for a while, death chime, original caps. But beside that seems in great condition. I did a recap and indeed after cleaning, the motherboard looks fine, almost like new. Great! Recapping done nicely, no surprises, except... it's still doing the death chime. Ugh. And I can't get any video, so no error code to read, I've litteraly no idea what's going on here. Here is few things I should check though: This reversed capacitor thing on the LCIII: Check rails voltage
  2. I've got some schematics, unless I'm wrong this is not the case on the IIsi. But I missing a page just near the part with the 2 Sony chips. I'm definitely going to check this first, I repaired a LCII with the same behaviour due to a bad ground connection on a chip managing the reset line. I don't know which part is responsible for the reset, it looks like it's the MC34064 and the 68HC05.
  3. Here is a small update, The leak as done a nasty job, the corrosion is quite heavy. Before doing a first test after recap, I was pretty sure it ain't be successful, alas, this IIsi didn't prove more wrong. Using an ATX PSU and matching the power connector pinout, I was able to start the computer but so far: no chime white screen no access on floppy/hard drive Points I've checked so far: 12V seems fine 5V seems fine too On board ROM and jumper properly set PRAM battery is good So I'll be going back to the w
  4. Hello there With lockdown I decided it's time to dig into some long post-phoned repairs, start with the mighty and wicked fast the "LC" look-alike Macintosh IIsi! I bought it on ebay for a fair price, it was out of order of course, but it was, electronics aside, in a good condition. This one is almost a stock one with a 40MB disk, a Nubus adpater + FPU (MC68882) card and a Asante Ethernet card The amazing TO DO list for this IIsi Clean and recap the PSU, which was just soaking in his own "cap-goo". Yikes. Clean and check the floopy drive
  5. Unfortunately it’s not an adapter problem, I used one to force the video mode at boot, and the one I use works fine with others LCs. I can’t get my Apple Display to show you a picture of what is displayed. But you can definitely see the happy mac then the desktop, but the video is totally messed up since the screen doesn’t get the hsync. I only have a lcd but it won’t display a thing in this case, it’s totally binary, either the signal is good, either it’s bad and nothing is displayed. So I need to find out which part on the motherboard failed to deliver the H
  6. Hello LCs enthusiasts! I recently get one of my LC475 unit out of storage in order to fix it and sell it. (Need to make some space ) Unfortunately, despite everything seems fine, the video output is missing HSync. PRAM battery is good I used a VGA adapter with DIP switches to force the video mode (so I can expect particulars readings) There is RGB signals and the VSync signal is a strong, stable and clean 66Hz (totally what I expected), checked with an oscilloscope. Motherboard and PSU fully cleaned and recapped. No broken trace found.
  7. I've planned to take some high-res pictures of my board this week-end. Yes, last paragraph of the "Prodigy RAM modules" section. Note that PALs and gate-array are OTP (one-time programming) so if it's mandatory to upgrade them we'll need new-old stock or replacement, and of course the actual logic implemented. First step is to provide at least the ability for everyone to upgrade to 4MB. Then develop some open source alternative tools for the prodigy more System 7 friendly, and even some customization tools.
  8. Hello! I recently got a Levco upgraded SE and decided to dig into it. I've done some digging into the board ROM and found few things. For exemple you can start the on-board self-test with the interrupt button and the following command: G 600056 But will focus on the RAM upgrade since it's the most usefull part for now. I bought a 68851 and plugged it into the Prodigy board in place of the BMMU (the not-a-chip with the levco or supermac sticker on it). This will allow me to upgrade the RAM up to 32MB, but this mean I should build my own memory board. I've got
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