first, the board. it is an obscure wavetable synthesis card for the Apple II from 1983. (forgot to mention this, but the music album came with the card)
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first, the board. it is an obscure wavetable synthesis card for the Apple II from 1983. (forgot to mention this, but the music album came with the card) 31 comments
after setting up the scale factors for the images (in DPI), KiCad 7 can import them in the correct scale directly into the layout. then i add a few parts to the schematic, place a few footprints on the layout, and start hooking up wires. i'm starting with +5V and ground since those are easy. so i just add a wire at a time to the schematic, propagate it to the layout, and make sure that it matches the existing traces. if there is any ambiguity, i just move on to the next trace. eventually i use a process of logical deduction to resolve that. one of the chips is a mystery chip -- it has been marked "862130" but that is not the real part number. the person who owns this board pulled the chip out and found this underneath! how rude... 😆 these are the pin connections i've deduced based on the rest of the board design. this chip seems to take over the Apple II's address lines and it copies sound samples over to the four DACs on the card. almost like a DMA controller. hmmmmmmmmmmm. 🤔 i've got it! it perfectly matches the pinout of the MC6844 DMA controller! mystery solved. @tubetime you’ve heard of an op amp but what about a pop amp??? @tubetime I used to have an old Xenix multi-user system that contained a *lot* of chips. Like a full megabyte of memory on a single board (12" square) with dozens of chips. Plus chips on the mainboard, chips supporting the system bus... @tubetime Presumably you also had a photo of the front, to see where the components are placed? (Lovely thread!) |
naturally, i don't have a physical board, but i have a blurry photo of the back. and, of course, the *artwork* for the top layer. which is great, since i can see traces that would normally be obscured by chips and other parts.