My First Trip to “The Computer Doctor”

The first personal computer I owned was an IMSAI 8080 kit computer that I bought and put together in December 1975.

Putting the IMSAI kit together involved a lot of soldering:

  • Soldered all twenty-two slot S-100 bus connectors onto the non-solder-masked motherboard
  • Soldered the front panel circuit board, Intel 8080 processor board and two 4K static RAM boards (lots of chips, connectors, resistors, capacitors, etc.)
  • Soldered the power supply with its large capacitors
  • Visually inspected all of the boards, motherboard, checked things with a voltmeter.
  • Assembled the Front Panel involved snapping on the cool looking blue and red paddle switches and the power switch, inserting the boards into the S-100 connectors.

It was time to plug in the power cord and turn the computer on for the first time (while crossing my fingers, toes, legs and eyes). When I turned it on, the front panel LEDs did light up, but pressing the stop and reset panel switches did nothing. There was no smoke or smell (always a good sign). I looked again at the boards. I pulled out and plugged back in the boards and tried again. No Joy!

I was a member of the Southern California Computer Society (SCCS) which met monthly at the TRW Space Park campus in Redondo Beach California (Note: at the time I was a real time Data General Nova assembly language programmer for a division of TRW – TRW Data Systems in El Segundo California). The monthly meeting was a place to talk about computers, buy kits, trade parts and keep up to date on what was happening in computing outside of work.

At the next monthly SCCS meeting at TRW Space Park (Redondo Beach), I left the computer with one of the vendors at the Saturday meeting, “The Computer Doctor”, who said he would find any soldering or component problems, get it running and give me a call. A week later, I got the call and the computer doctor said he had found some bad soldering, some solder that had spilled across some of the motherboard and computer board traces. I drove to his house and picked up my IMSAI. The doctor also suggested that I buy a bus terminator board from Godbout Electronics to “quiet” the non-solder-masked motherboard.

I brought my IMSAI back to my apartment, plugged it in, pressed the stop and reset paddle switches and my personal computer was ready for me to put some Intel 8080 instructions into memory and press the Run button. The IMSAI manual had a simple starting machine code program to display the LEDs on the front panel. It also had a “game” example where you had to try and turn the LEDs all off our on as they were changing.

The fun fact is that “The Computer Doctor’s” actual name was George Tate. Some of you remember George Tate as the co-founder of Ashton Tate Software and dBase fame.

I still have that original IMSAI 8080 computer and the last time I took it our and turned it on (a couple of years ago), it still worked.