1-4
Figure 1-2.—Point-to-point wiring.
Vacuum-tube circuits proved to be reliable under many conditions. Still, the drawbacks of large size,
heavy weight, and significant power consumption made them undesirable in most situations. For
example, computer systems using tubes were extremely large and difficult to maintain. ENIAC, a
completely electronic computer built in 1945, contained 18,000 tubes. It often required a full day just to
locate and replace faulty tubes.
In some applications, we are still limited to vacuum tubes. Cathode-ray tubes used in radar,
television, and oscilloscopes do not, as yet, have solid-state counterparts.
One concept that eased the technician's job was that of MODULAR PACKAGING. Instead of
building a system on one large chassis, it was built of MODULES or blocks. Each module performed a
necessary function of the system. Modules could easily be removed and replaced during troubleshooting
and repair. For instance, a faulty power supply could be exchanged with a good one to keep the system
operational. The faulty unit could then be repaired while out of the system. This is an example of how the
module concept improved the efficiency of electronic systems. Even with these advantages, vacuum tube
modules still had faults. Tubes and point-to-point wiring were still used and excessive size, weight, and
power consumption remained as problems to be overcome.
Vacuum tubes were the basis for electronic technology for many years and some are still with us.
Still, emphasis in vacuum-tube technology is rapidly becoming a thing of the past. The emphasis of
technology is in the field of microelectronics.
Q4. What discovery proved to be the foundation for the development of the vacuum tube?
Q5. Name the components which greatly increase the weight of vacuum-tube circuitry.
Q6. What are the disadvantages of point-to-point wiring?
Q7. What is a major advantage of modular construction?
Q8. When designing vacuum-tube circuits, what characteristics of tubes must be taken into
consideration?
