Second channel: Logical reasoning wins! Looking at symptoms allowed me to fix this Mac (Patreon)

Logical reasoning wins! Thinking through the symptoms allowed me to fix this Mac

In this video I repair a Mac 512k motherboard with an unknown RAM expansion card on it. In part 1, we looked at two Mac motherboards with unusual RAM expansion cards. The Mac 128k motherboard worked, but I left the Mac 512k motherboard for another video. This is that video! Figuring out what was causing this motherboard to not boot and display video issues required me to study schematics and try to understand the architecture of these early Mac machines, and it paid off! Part 1: Part 2: This part! -- Video Links ROM Matrix: https://docs.google.com/spreadsheets/d/1wB2HnysPp63fezUzfgpk0JX_b7bXvmAg6-Dk7QDyKPY/edit#gid=840977089 Sad Mac Error codes: https://tinkerdifferent.com/resources/sad-mac-error-codes.82/ Macintosh 128k technical documentation: http://bitsavers.informatik.uni-stuttgart.de/pdf/apple/mac/prototypes/1983_Twiggy/Macintosh_Hardware_Memory_Map_19830413.pdf ROM Disassembly: https://www.bigmessowires.com/rom-adapter/plus-rom-listing.asm PicoRC: https://github.com/dekuNukem/PicoRC/blob/master/README.md https://www.tindie.com/products/dekunukem/picopsu-adaptor-for-ibm-5155-ibm-pc-compatibles/ Adrian's Digital Basement Merch store: https://my-store-c82bd2-2.creator-spring.com/ Support the channel on Patreon: https://www.patreon.com/adriansdigitalbasement Adrian's Digital Basement (Main Channel) https://www.youtube.com/channel/UCE5dIscvDxrb7CD5uiJJOiw My GitHub repository: https://github.com/misterblack1?tab=repositories -- Tools Deoxit D5: https://amzn.to/2VvOKy1 http://store.caig.com/s.nl/it.A/id.1602/.f O-Ring Pick Set: (I use these to lift chips off boards) https://amzn.to/3a9x54J Elenco Electronics LP-560 Logic Probe: https://amzn.to/2VrT5lW Hakko FR301 Desoldering Iron: https://amzn.to/2ye6xC0 Rigol DS1054Z Four Channel Oscilloscope: https://www.rigolna.com/products/digital-oscilloscopes/1000z/ Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier: https://amzn.to/3adRbuy TL866II Plus Chip Tester and EPROM programmer: (The MiniPro) https://amzn.to/2wG4tlP https://www.aliexpress.com/item/33000308958.html TS100 Soldering Iron: https://amzn.to/2K36dJ5 https://www.ebay.com/itm/TS100-65W-MINI-Digital-OLED-Programmable-Soldering-Iron-Anti-static-Structure/113382669853 EEVBlog 121GW Multimeter: https://www.eevblog.com/product/121gw/ DSLogic Basic Logic Analyzer: https://amzn.to/2RDSDQw https://www.ebay.com/itm/USB-Logic-DSLogic-Basic-Analyzer-16Ch-100MHz-4Ch-400MHz-Xilinx-Spartan-6-FPGA/202543965672 Magnetic Screw Holder: https://amzn.to/3b8LOhG https://www.harborfreight.com/4-inch-magnetic-parts-tray-90566.html Universal ZIP sockets: (clones, used on my ZIF-64 test machine) https://www.ebay.com/itm/14-16-18-20-24-28-32-40-pin-IC-Test-Universal-ZIF-Socket-Fs/303206721971 RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI) http://www.retrotink.com/ Plato (Clone) Side Cutters: (order five) https://www.ebay.com/itm/1-2-5-10PCS-Micro-Scissor-125mm-PLATO-170-Electronics-Cutter-Side-Cutting-Pliers/163458746184 Heat Sinks: https://www.aliexpress.com/item/32537183709.html Little squeezy bottles: (available elsewhere too) https://amzn.to/3b8LOOI --- Instructional videos My video on damage-free chip removal: https://www.youtube.com/watch?v=XQVjwPsVFd8 --- Music Intro music and other tracks by: Nathan Divino @itsnathandivino