Apple Macintosh 128k & Imagewriter
Sitting in the book arts lab I almost fell over as fellow docents carried in a beautiful Apple Macintosh 128k and sat it down in front of me.
Knowing I used to work for Apple the computer was brought in and placed before me partially in jest, it had been assumed that the machine probably didn't work as it had been packed away in a box for who knows how long up back in some rafters.
Before me lay the machine, keyboard, mouse, external floppy drive and a stack of 3.5" floppies. Not knowing quite what to expect we began plugging in the components and connected the machine to power. Flipping the power switch presented me with a flashing disk icon.
Momentarily disappointed but not surprised I suddenly remembered that the Macintosh 128k had no internal storage device. I grabbed the 3.5" System Disk, inserted it into the machine and the computer booted to the Finder quickly and quietly. AMAZING! I entertained myself in my mind comparing the boot speed to later operating systems, and not until solid state drives and multi-core processors do we begin to come close to how quickly this thing starts up.
I began playing with Mac Paint and thought to myself what a game changer this was to graphic artists in 1984 when it was introduced. Up to this point computers sophisticated enough to create digital artwork this well were both difficult and extremely expensive, upwards of $10,000 in fact. This $2,500 machine made it possible to bring digital desktop publishing to every business.
As I started on some type setting in all the bitmap glory of fonts like Venice, Chicago, London, Geneva, New York and Toronto yet another surprise was dropped on the desk next to me. It was the Apple ImageWriter, a dot matrix printer released in 1983. I had absolutely no hopes that this was going to work at all. I had been lucky enough the computer and its other components were functional but I know what happens, even with modern printers, when they sit for more than a few months without use.
We shut down the computer, plugged in the printer to power and connected the serial cable to the back of the Macintosh. Low and behold the printer actually turned on. Power, however, does not necessarily mean that it will print. I fired up Mac Paint again to tried a test print. Nothing. I tried again just to print the catalog and this time we got a pulse. The printer head ground across the paper and left an impressed and scratched dusty image. This is the last that it prints and we got nothing else out of it.
I worked on Apple computers for 3 years and have always liked to tinker but I had never taken apart an Apple machine this old and never an Apple printer. I decided to be bold, what did I have to lose? I stripped the machine down component by component checking all the cables, cleaning all the boards and checking all the capacitors. After 3 hours of looking like I knew what I was doing I had the printer back together and fired back up.
Making another attempt to print I was dumbfounded that I actually got it working again. Not only was the header working again but the ink ribbon mysteriously had a little life left to it. I was not out of the wood yet as although the machine was printing it was having a heard time aligning the images and words as it would drop line by line down the paper.
Once again I partially disassembled the printer, this time cleaning the rails and metallic pulley system that the printer header rides along and greasing the rails. The header originally rode on felt pads but as these were in very poor condition and irreplaceable a silicon lube did the trick just as well.
Snapping everything back together I gave the print one last try. SUCCESS. The image came out beautifully, or as beautiful as dot matrix can come out on a 90% dry ink cartridge.
a Motorola MC68000 microprocessor at clock speed 7.8336 MHz
64KB of ROM in two chips containing parts of the operating system
128KB of RAM in 16 chips
eight TTL chips implementing a video and sound DMA controller, plus
two TTL chips providing a 16-bit video buffer (74166 type)
one PAL chip generating video timing signals (LAG)
two TTL chips providing an 8-bit Pulse-width modulation sound driver (74LS161 type)
two analog chips providing sound amplification (MC14016 switch, LF353 op-amp)
a Zilog 8530 chip controlling two RS-422 buses through two driver chips
an Integrated Woz Machine 400 KB floppy disk controller plus support PAL (ASG)
a 6522 VIA bridge chip connecting to the keyboard and clock
an Apple real-time clock chip plus a 32.768 kHz quartz oscillator
an Intel 8021 microcontroller in the keyboard
bus control and extra logic including
two PAL chips to activate the other chips (BMU0/1)
two PAL chips to convert the 16 MHz clock to other timing signals (TSM, TSG)
two TTL chips buffering the RAM to the 68000 (74LS244 type)
some inverters (74LS04 type)