Macintosh SE/30 Logic Board Schematic
The complete circuit diagram for the Macintosh SE/30 main logic board — a ten-sheet KiCad redrawing of Apple engineering drawing 050-0253-01, made by the macse30mlb project and dated 26 July 2022. Apple's own scans of 050-0253-01 are barely legible; this redraw is the practical reference for anyone tracing a fault on an SE/30 board, and Recap-a-Mac recommends it for exactly that purpose.
It is released under the MIT licence, which is why it can be hosted here rather than merely linked.
What is on each sheet
edit- CPU + FPU — the 68030 at UK8 and the 68882 socket at UI5, with the reset, halt and bus-error signals.
- GLUE + RAM SIMMs — the glue logic chip UI8, the RAM signal PAL UH7 and the SIMM sockets.
- ROM + RAM Muxes — the ROM SIMM connector and the F258 multiplexers above it.
- Video Interface — the video RAM, the video IC UK6 and the Ux8 multiplexer row.
- VIA1 + VIA2 + RTC + ADB — UK12, UK11, the real-time clock with its 32.768 kHz crystal Y1, and the ADB transceiver UL11.
- SWIM + SCSI Interface — the SWIM floppy controller UJ11 and the NCR 53C80 SCSI controller UI12.
- Serial Interface + Sound Interface — the line drivers UD12 and UE12, the Apple Sound Chip UE10 and the Sony sound chip UB11, with the 16.9344 MHz crystal Y3.
- Power Connector + Pullups + Pulldowns — connector J12, the "Power & Video Connector", plus the pull-up packs RP7, RP8 and RP9 and the 1 A fuse F1.
Why it matters for repair
editSheet 9 gives the J12 pinout, which is what makes it possible to bench-power a bare SE/30 logic board without guessing: pins 1–5 and 8 are ground, pin 6 is −5 V, pin 7 is −12 V, pins 9, 10 and 11 are video out, horizontal sync and vertical sync, pins 12 and 13 are +5 V and pin 14 is +12 V. Getting that wrong on a bench supply destroys a board.
The same sheet identifies fuse F1 as a 1 A part — the usual reason an otherwise healthy SE/30 has a dead keyboard and mouse — and gives the pull-up pack values, including RP7 at 1 kΩ, which pulls up !BERR.
Download the schematic here: File:Macintosh SE30 Logic Board Schematic Redraw 050-0253-01.pdf