This article is for those who are interested in troubleshooting tips and those are interested in a career as an electronic technician. The first paragraphs of this article covers the duties of an electronic technician who has received an Associates Degree in Electrical Engineering. It assumes that the reader has a knowledge of electronics.
Duties of an Electronic Technician
The Associates degree is a two year degree from a technical institute or a college. The two years provide training in electrical and electronic theory. One of the jobs a graduate can get is a job as an electronic technician.
I worked for seven years as an electronic technician. My duties included testing printed circuit boards and testing complete electronic instruments. In both cases, As a production test technician, I would test the board or instrument according to a written procedure and adjust it per the procedure so it performed within the specifications. I would also troubleshoot any problems that I encountered. I only spent a few months as an engineering technician. I assisted an engineer troubleshooting a circuit.
Tips on Troubleshooting Electronic Circuits
These tips assume that you are working as a production test technician. However, many of the tips apply to all electronic troubleshooting.
The very first thing you should do with any printed circuit board that isn’t working properly is to check for solder splashes. I have found a hairline solder splash on a number of printed circuit boards I have tested. While you are checking for solder splashes, also check the condition of the soldered connections. Make sure they are all shiny and smooth. A cold solder joint is one where the rosin forms an insulator between the solder and the wire.
Also check to any DC power supplies on the board to ensure they are putting out the correct voltage. After checking the power supply outputs with a digital voltmeter, check those same outputs with an oscilloscope. Look for ripple or noise on the output.
If you suspect a faulty component on a certain part of the circuit, first inspect the soldered soldered pins of the suspected component and other components associated with it. Without unsoldering the component, look for solder splashed under the component or between the soldered pins. Also use an oscilloscope to examine the voltage from the power supply. Again check for any noise on the DC level.
Also measure use a multimeter to measure the voltage, if any, between the common pin on the component and the common output of the power supply. I once measured two volts between the power supply common and the common pin on a suspected component. That voltage was due to a faulty connection.
Remember that there are many causes of a low voltage on any input or output pin of a component. Among those causes is a common pin that is not at the same voltage as the power supply common, a power pin that is not at the same voltage level as the power supply output and noise on the power pin or on the common pin.
One way to find noise being induced into the common trace is to use the oscilloscope to measure the signal, if any, between the common output of the power supply and the common pin on the suspected component.
After you are convinced that the power and common connections are okay and the power supply output is within specifications, you can start looking at the signals on the pins of the suspected component.
When looking at waveforms, there are a number of potential issues to be aware of. Among those issues are both the high and the low voltage levels of the waveform and any noise that might exist on the waveform. If it is a digital input or output, you want to inspect any overshoot or undershoot, any ringing on the edge of the pulse and the rise time of the pulse.
A printed circuit board, one technician was troubleshooting, wasn’t working right. He eventually got to the point where he was checking the through-holes on the board. A through-hole is a plated hole which connects a trace on the top of the board to a trace on the bottom of the board. A trace is a conductive path on the printed circuit board. In this case, there were hairline fractures in the through-hole plating that acted like tiny capacitors when the circuit was operating. He soldered small leads in all through-holes to resolve the problem.
If the symptoms of a problem are constantly changing, don’t troubleshoot any symptom. Instead troubleshoot why the symptom is changing and you’ve found your problem.
The weirdest problem I had was in a constant amplitude variable frequency oscillator. Every time I varied the output frequency, the output signal would collapse and then slowing build back up to the rated voltage. When I took the oscillator apart, I found that one of the vacuum tube sockets had wires wrapped around it’s pins, but not soldered. I soldered the wires to the pins and the problem was resolved.
One technician was sent on a field service trip in response to a complaint from the customer that the weighing scale reading was going crazy. The technician found that the reading would go crazy any time the operator talked on the walkie talkie he used to communicate with the workers outside.
I hope these tips help the reader when troubleshooting electronic equipment.