REPAIR STATIONS

2-6 those that should be observed when troubleshooting equipment containing semiconductor or other voltage and current-sensitive devices. Voltage and resistance tests of resistors, transistors, inductors, and so forth, are usually effective in locating complete failures or defects that exhibit large changes from normal circuit characteristics; however, these methods are time-consuming and sometimes unsuccessful. The suspect device often must be desoldered, removed from the circuit, and then retested to verify the fault. If the defect is not verified, the device must be resoldered to the board again. If this procedure has to be repeated several times, or if the board is conformally coated, the defect may never be located. In fact, the circuit may be further damaged by the attempt to locate the fault. For these reasons, the device should never be desoldered until all possible in-circuit tests are performed and the defect verified. Q7. List the three groups of test equipment used for fault isolation in 2M repair. Q8. What test equipment continuously monitors electronic systems? Q9. NELAT and VAST are examples of what type of test equipment? REPAIR STATIONS In addition to the requirements for special skills, the repair of 2M electronic circuits also requires special tools. Because these tools are delicate and expensive, they are distributed only to trained and certified 2M repair technicians. 2M repair stations are equipped with electrical and mechanical units, tools, and general repair materials. Such equipments are needed to make reliable repairs to miniature and microminiature component circuit boards. Although most of the tools and equipments are common to both miniature and microminiature repair stations, several pieces of equipment are used solely with microminiature repair. Precision drill presses and stereoscopic-zoom microscopes are examples of microminiature repair equipment normally not found in a miniature repair station. A brief description of some of the tools and equipments and their uses will broaden your knowledge and understanding of 2M repair. The 2M repair set consists of special electrical units, tools, and materials necessary to make high- reliability repairs to component circuitry. The basic repair set is made up of a repair station power unit, magnifier/light system, card holder, a high-intensity light, a Pana Vise, and a tool chest with specialized tools and materials. As mentioned previously, stations that have microminiature repair capabilities will include a stereoscopic-zoom microscope and precision drill press. REPAIR STATION POWER UNIT The repair station power unit is a standardized system that provides controlled soldering and desoldering of all types of solder joint configurations. The unit is shown in figure 2-1. Included in the control unit's capabilities are: