Racintosh Plus

4 months of work just to make a stupid pun.

1986 Macintosh Plus at home in my music studio.

    I own a Macintosh Plus from 1986, I found it in the mid 2000's on my college campus on a free-to-a-good-home shelf (Mad Marc's shelf in the chemistry building) in great shape and with its mouse, keyboard, and an HD-20 external hard disk drive.
    That silly computer has been on the journey with me ever since, leaving college with me and occupying a spot in all of my music studios in all of my homes.  I even used it in the production of my first full-length studio album Church Music For Robots.
    As much as I adore this little champion, it has some glaring issues that I was struggling to ignore:

It is big and bulky.
It eats up an awkward corner in my studio right now and there really isnt a good place for the mouse and keyboard to live when I need to use it.

It is old!
The components are nearly as old as I am and could fail at any moment.  It has already blown through a few CRT drive capacitors and that stupid RIFA cap across the AC input lines, the screen flickers really bad no matter what I tweak, and the hard drive works by spinning 40 year old plates made of rust.

This thing gets pretty hot.
I don't have the best AC in my studio, and this beige thermal generator belches out a lot of heat from the power supply as it drives that dumb flickering screen.

    This just wont do!  I ought to make a rack-mounted version of this computer so it can fit cleanly in my studio rack cabinets along with all my other conveniently packaged gear.  I will even give it a sleek look and a clever name, something like Racintosh Plus...   Hahaha yeah that's pretty funny.

Logic Board.
      The brains of Racintosh Plus is a 1986 Macintosh Plus logic board (oh don't worry, my original computer is perfectly safe, this one is a spare board).  R8 was clipped to allow the full 4 MB of system RAM, but I left one lead still in place so the resistor doesn't get lost.  A diode (IN4001) was soldered into position CR1 to provide +5V power to the SCSI port.  For some reason that diode was left out of the manufactured board, even though it appears in the schematics.  SCSI power would be needed to run the internal hard drive system I planned on using.  
      Since the end goal was to get everything to fit in a single 1U high rack chassis, I was limited in internal height to around 1.5", and that would have to include the SCSI system I wanted to stuff in.  As a result of those size constraints, I was forced to remove the main pin header that connects to the analog board from the logic board, and solder wires directly to the pads.  Hot glue keeps the whole mess secured in place.  I won't provide a picture of that because it is ugly.

Video Converter.
      A 9 inch black and white CRT monitor will not fit in a 1U high rack chassis, nor will its power supply circuitry.  Plus, hasn't CRT been falling out of favor politically lately?  (Har har har).  Racintosh Plus uses an RGBtoHDMI Video Interface Board and Raspberry Pi Zero to convert the Horizontal Sync, Vertical Sync, and TTL Video Source signals from the Logic board to a pixel-perfect HDMI signal.  My fancy-dancy college degree in fingerpainting that I only technically completed didn't help much when reading the documentation for the interface wiring, but I was able through brute force to figure out where the wires were supposed to go.  If you run into trouble, The TTL Video source output on the Logic Board of a Macintosh 128k, 512k, and Plus is supposed to connect the the pin on the interface labeled grn3.  

Internal Hard Drives.
      There is not much room for an internal hard drive in the chassis, nor did I want to tether Racintosh to an external HD-20 that is bulky and can fail at any moment.  For internal storage, I chose to utilize a BlueSCSI V2 50-Pin Desktop Board with a Joe's Clipper Plus that snaps directly onto the SCSI controller on the Logic Board.  I wanted the SCSI board to sit directly over top the main Logic Board header and ROMs, so I cut the ribbon cable on the clipper plus way down and re-crimped the connectors.  I cut a plastic sheet cover for the back of the board so nothing would short out on the top cover of the rack chassis.
      The BlueSCSI allows disk image files (.hda) to be read by the Macintosh system as SCSI drives.  Racintosh has two such drives running, a 2GB main drive and a 512MB utilities drive (the utilities are a package offered with the BlueSCSI system).

Floppy Drive Emulation.
    Floppy disks were always going to be a big challenge for this project.  I only have the one drive that is inside my Mac Plus, it is old as dirt, big, has a lot of fragile moving parts, is probably expensive to find a spare on the web, and let's be honest I don't even have mac formatted medium format disks anyway.  Racintosh Plus uses a Floppy Emu for mounting disk image files (.dsk) from a microSD card.  I needed the LED display, controls, and SD card slot for the Floppy Emu to all be accessible on the front panel, so modifications needed to be made.  The display board is detachable, so I was able to solder on shortened Dupont connector wires to the main board to break the display off and mount it.  I made a new control board with the push buttons and a power LED that I wired to points on the main board.

CMOS Battery.
      The original Macintosh Plus uses a 4.5V alkaline battery (A21, A21PX, A133, APX21) to power the CMOS chip and timekeeping circuit.  I wanted to use rechargeable AA batteries instead, and opted for a Macintosh Battery Replacement Kit.  I soldered dupont wires to the terminals and have it connected from the battery input on the Logic Board header to ground.

Speaker.
      A new 0.25W 8Ω speaker was placed on the bottom panel of the rack chassis and connected to the motherboard and ground with Dupont connector wires.  The 1/8" headphone connector on the back of the Logic Board was not passing audio to the speaker when nothing was plugged into it due to oxidized metal contacts inside the jack housing (it contains a microswitch to pass audio to either the jack or the internal speaker, but not both).  Some deoxit cleaned the contacts right up!

Mouse and Keyboard.
      I wanted to have the mouse and keyboard ports accessible on the front of the rack, so I removed the keyboard port from the board and soldered in a new one with wires so it can extend past the board.  I built a break-out board the replaces the deglitching pack serving the mouse port (U9A), there is a socket in its place on the board that the breakout plugs into, it holds the deglitching pack and the ribbon cable connections serving the front connector.

Power Supply.
      There was no room in the rack chassis for the original Analog Board (not that I even had a spare one, one of the side goals of this project was to keep the original Macintosh Plus unmolested), and without a CRT monitor a lot of the components on that board would have been unnecessary anyway.  The power supply for Racintosh Plus is a Mean Well RT-65B, outputting 5V, 12V, and -12V, with a maximum power output of 65W. A 6-pin molex connector ties the power and ground from the power supply to the Logic Board.

      The electronics are only half of the Racintosh Plus project, all the circuits, modules, and wiring needed to fit into an empty 1U (1.75") high 19" rack mounted chassis.  This would require a computer model to work out all of the sizes, clearances, and spacial relationships, then to design the mounting brackets, front panel pieces, buttons, and other parts.

Computer Model.
     My weapon of choice for 3D modeling is Sketchup.  The rack chassis and all of the circuits and components were carefully measured and built in the computer, providing a highly accurate model of Racintosh Plus.

Modifying the rack chassis.
     Openings needed to be cut into the rack chassis front and back for ports, buttons, the floppy disk emulator system, and mounting brackets.  I don't own a CNC machine, so I had to carefully mark out the openings on the metal parts with pencils and painter tape, then grind them out by hand with a Dremel tool.  Deburring, sanding, and touch up painting helped hide all my crimes.  The front panel openings will also have 3D printed faceplates with flanges that will cover up any small mishaps.

3D Printing Parts.
     Many of us have a friend with a 3D printer.  Mine is called Clark (friend, not the name of the printer, he uses one made by Bambu Labs).  He offered to print my mounting hardware for me, so I used my Sketchup model to design and export all of the pieces.
     To avoid putting stress on the plastic and causing breaks or cracking, I chose to seure all of the circuit boards using brass screw posts that would be pressed into hexagonal sockets with a bit of super glue to secure them.  The mounting brackets would then be screwed to the bottom of the rack chassis.

Decals.
     Many of us have a friend with a Laser Etching Machine.  Mine is called Brenden (friend, not the name of the laser, he uses one made by xTool).  He offered to etch the text and port symbols onto the front and back panels, but his laser etching machine is on crack and doesn't like to print where you tell it to.  We found this out the hard way and I had to sand and repaint the front panel.  As a plan B, I designed a sheet of silver rub-on decals and had it printed and shipped.

     As the guts and bones were busy settling into place, I was hard at work figuring out what was going to run on Racintosh Plus and how I was going to get everything to work properly.  I wanted a computer that could run a large variety of production applications, mostly music design software, but also electronic and image design tools.  Some old vintage games would be a nice treat, too!

System configuration.
     Racintosh Plus runs System 7.1 from an internal 2GB SCSI drive image on an SD Card on the BlueSCSI board.  The system was installed using disk image files on a spare Floppy Emu box, and went lightning fast due to there being not bottle neck in transfer speeds between the "floppy drive", the CPU, and the "hard drive".

Virtual twin.
     To test our software and create floppy disk images, I created a virtual version of Racintosh Plus on my laptop using Mini VMac.  It runs the same System 7.1 and has various versions of StuffIt Expander installed, importfl and exportfl for getting files in and out of the classic Mac System environment.

Additional features and settings.
     The BlueSCSI board that Racintosh Plus offers wifi connectivity to my network, which it passes along to the computer pretending to be a SCSI AppleTalk modem.  With the wifi antenna being trapped inside an aluminum case surrounded by audio interfaces and synthesizers, signal strength is not the best and I can get about 70% ping successes at best.  It is my hope that in the future I can optimize the signal strength and run Racintosh Plus remotely using VNC.
     Another hurdle to overcome on Racintosh Plus is setting the date, the original system stores the date and time in a single 32-bit integer for seconds, but truncated to 100 years, starting in 1920.  This means when I try to set the year to 2025, it cycles back to 1920 as soon as I pass 2019.  Thankfully I found a system utility that patches the time/date system called DateFix - 2020Patch (available as part of an image pack available for download from BlueSCSI's website).