It’s time for another 68k Mac repair. I thought it would be a quick and easy fix, but this turned out to be a but more mysterious.
— Info
Microbug:
DM (dump memory)
SM (set memory)
Video page:
U15D VIA 6522 PA6 Pin 8 to U4G 74AS253 Pin 4
From microbug, I was writing to
3F A700 Screen Buffer 1
00 0000 – 3F FFFF 0M – 4MB Total address space
00 0000 – 0F FFFF 0M – 1MB
00 0000 – 07 FFFF 0K – 512k
xx FCFF Screen1 memory end
xx A700 Screen1 Memory start
xx 7C7F Screen2 Memory End
xx 2700 Screen2 Memory Start
— Links
Decoding Mac error codes for the 128/512/Plus:
https://tinkerdifferent.com/resources/sad-mac-error-codes.82/
Adrian’s Digital Basement ][ (Second Channel)
https://www.youtube.com/channel/UCbtwi4wK1YXd9AyV_4UcE6g
Support the channel on Patreon:
https://www.patreon.com/adriansdigitalbasement
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:
121GW Multimeter
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 chip removal without damage:
— Music
Intro music and other tracks by:
Nathan Divino
@itsnathandivino
About The Author
