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circuit debugging

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I have only listed that term "debug" for programming, where something goes wrong and you try to find where is the source of the error.


Havent listed that termn in electronics, anyway, I think you should know what will be the output of a circuit and what is the input of a circuit in order for analize the results and see if somehing is wrong... I guess.
 
Troubleshooting - "Debuging"

Debuging a circuit is normally called troubleshooting. There are a number of techniques that can be used. Sometimes multiple techniques may be necessary.... (this list is NOT all inclusive)

1. FIRST. Check for the obvious. No power, switches set wrong, bad fuse, bad cable, funny odor, black/chared parts, etc. Use common sense, as well as your senses. Is anything running really hot? ? (don't get burned!) Are there any bad solder connections/bridges/shorts? Are all of the voltages in the power supply correct? Is there an input? (if not, there usually is not an output!) And by the way, only open the equipment up if one cannot find anything on the outside that caused the problem. I've worked on tape decks and when the cover was opened noticed that the reason it "DOES NOT WORK" was the pause button was depressed......

2. Symptom/Function - analyze the symptoms that the circuit is exhibiting, then figure out which part of the circuit has that function - this is a starting point used in large systems. (computers, TV's, equipment with lots of "stuff" in it! Quite often this is followed up with:

3. Signal tracing. Put in a signal, and follow it through the circuit. An excellent example is an amplifier. Put in a signal you KNOW - i.e., a 1000Hz tone - then follow it as it travels through the amp. A 555 timer can be used instead of a signal generator, and in fact any audio signal can be used that is relatively constant. (A walkman? MP3 player?) Use a small amplified speaker to do the tracing - keep in mind that it may become rather loud as you get towards the output stages. This technique will work in many types of circuits, including logic circuits assuming one is applying the correct input signal, and using an appropriate signal tracing device.

4. Voltage analysis. This is used when one has the schematic drawing with voltages listed. Normally (unless other wise noted) voltages are measured with respect to ground. When analyzing a simple circuit, one should be able to use knowledge of electronics to figure out what voltages should be present. (Series - parallel rules, Kirchoff, Transistor analysis, etc.)


5. Resistance analysis. This is used when one has the schematic drawing with resistances listed. Measure the circuit resistance - usually from the test point with the marked resistance to ground. Not used as much as voltage analysis.

6. Comparison. Take a good working device and compare it to the unit not working. Obviously only works when one has the known working unit.....

7. Goferbroke..... All else failing, check the device part by part. Start with the power supply and voltages - then start looking at things that carry alot of current, connectors, etc. Remember that if you have a burnt out resistor, they fail like a fuse - something made it burn out! Replacing it will only result in another burnt out resistor. Sometimes fuses wear out - they do run warm sometimes, and after a while (usually years) they will fail for no apparent reason.

8. If you are building a circuit, check your work. Are all the solder connections good? Are there any shorts or solder bridges? Are the parts good? Some devices can be damaged with either heat or static, and may have been damaged whilst installing. Also, if you downloaded the circuit, DOES IT REALLY WORK? it may look good on paper, but noone may have actually tried it! Get it checked out by some one that can help you figure that out...

MOST IMPORTANT - USE COMMON SENSE. Electricity can cause burns, death or just a funny gate and drooling. Don't end up looking funny!

Artr
 
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