WEEK 13

TITLE : Trouble shoot the component.

METHOD : 

      Simply put, trouble-shooting is the art and science of getting something to work. If you work in electronics then, at some level, you will be involved in trouble-shooting. If you are a repair-tech, trouble-shooting is the name of the game. If you are a designer, then you will have to "debug" your designs which means trouble-shooting of another sort. Trouble-shooting can be divided into two kinds of situations: repair and development.In repair, you know that the equipment you are trouble-shooting did, at one time, work. Then something happened that made it stop working. Maybe a component failed. Your job is to find out what went wrong and then to fix it.

      In development you are working on prototypes. Either new designs or modifications of existing designs. In such a case, when it doesn't work properly there are three possibilities. First, as in repair, there may be a faulty component. Second, the breadboard or prototype wasn't built according to design. Third, there may be a fault in the design. Usually, there is a combination of all three in an early prototype.

    We'll discuss some basic ideas of trouble-shooting that will apply to all situations. One principle should be stated right here: SAFETY FIRST. Don't do anything that may harm you, others, or the equipment you are working on. Remember that high voltage can cause burns, and a shock across your chest can stop your heart.

Instruction:

• Look for visual clues on the circuit board. Overloaded parts may show obvious burn marks. A glass fuse will turn dark if it’s blown. Examine the trace side of the board for burn marks, errant solder blobs, and broken traces.
• Study the schematic and understand the kinds of signals you expect to see from your circuit board. Determine what voltages, frequencies, and waveforms are produced at each point in the board.
• Turn your oscilloscope on. Connect the ground clip of its probe to a grounding point on the circuit board.
• Set the oscilloscope to the sweep speed that will best handle the frequencies coming from your circuit. Adjust the voltage range of your scope’s input channel to match what your schematic indicates. Set the channel’s coupling to DC and zero the horizontal trace.
• Turn your circuit on. Touch the oscilloscope probe tip to the various points you determined in step 1. Work forward in the circuit, from the power supply through any signal generation and amplification points. When you look at the power, observe that the voltage offsets you see on the scope are what the schematic specifies. If any part of the circuit is erratic or dead, the oscilloscope will reveal it quickly.

CONCLUSION :

Troubleshooting a circuit board is a challenging task. The first thing to do when checking out a faulty board is to look it over. You may see a broken wire or missing parts. Next, look at the circuit’s schematic and get an understanding of how it works and what signals you’d expect to see. Power up the circuit and probe it with an oscilloscope. The oscilloscope will reveal what’s working in the circuit and what’s not.