21180 Via Cota, Yorba Linda, CA 92887
714-779-0464 tom@madracki.com
I started in the computer industry in 1970 after graduating from Control Data Institute as a Computer Technician.
I had been a Hawk missile system technician during the Vietnam War and took my computer training using the
G.I. Bill. Originally I worked on large mainframe computers at companies like Bank of America and
the U.S. Forest Service, but over my career of 38+ years, mainframe computers got smaller and smaller,
evolving into mini's and then micro's. IBM PC's were a novelty at first, but eventually with the
advent of the Internet, became the mainstay that they are today. In the 1970's technicians had to
actually know how a computer worked and how to fix it by repairing the circuit boards, power
supplies or disk drives. The 1970's technician never worked on the mainframe's software,
that job was the responsibility of the system programmer or software engineers. Good hardware
technicians used machine language programs, written on the spot and hand entered into the mainframe, to troubleshoot computer problems.
A typical mainframe CPU was a group of thousands of PC boards wired together. There was no way to just "swap out" a bad board; there were just too many boards to "guess" which was the bad one. The technician used an oscilloscope to trace down the bad signal and follow it back thru the wiring diagrams to the failing circuit board. He would then remove the bad card and replace the failing transistor that was causing the problem. Integrated circuits had not been invented yet, so all troubleshooting was done at the transistor level. Today's Pentium CPU chips are made of two to three million transistors per core, all on a single silicone wafer. In the 1970 computer, it's thousands of transistors were located on thousands of circuit boards, in multiple cabinets , each the size of a large double door refrigerator. Some of these circuit boards had as few as two transistors on them and may have been used as a single AND gate or as complex as a FLIP-FLOP. Most computer repairs today are done by just replacing defective parts, but the real skill in today's PC world is knowing how to use and repair the software.