How to debug a new circuit board?
Measurement voltage method.
First of all to confirm that the chip power supply pin voltage is normal, followed by a variety of reference voltage to check whether the normal, in addition to the point of the work voltage is normal and so on. For example, when the general silicon transistor is turned on, the BE junction voltage is about 0.7V, and the CE junction voltage is about 0.3V or less. If a transistor's junction voltage is greater than 0.7V (except for special triode, such as Darlington tube, etc.), it is possible that the BE junction is open.
② signal injection method.
Add the signal source to the input, and then measure the waveforms of each point in turn to see if they are normal to find the point of failure. Sometimes we will use a more simple way, such as hand holding a tweezers, to touch the input at all levels to see whether the output response, which in audio, video and other amplifiers often used (but note that the hot floor Circuit or high voltage circuit, can not use this method, otherwise it may cause electric shock). If the first level did not respond, and touch a response, then the problem in the previous level, should focus on inspection.
③ Of course, there are many other ways to find the point of failure, such as watching, listening, smell, touch and so on.
"Listen" is to see whether there is any obvious mechanical damage to the component, such as rupture, burning black, deformation, etc .; "listen" is to listen to the work sound is normal, for example, something should not ring in the ring, the ring does not ring or sound Abnormal, etc .; "smell" is to check whether there is odor, such as charred taste, the smell of capacitive electrolyte and so on.
For an experienced electronic maintenance personnel, it is very sensitive to these scents; "touch" is to test the temperature of the device is normal, such as too hot, or too cold. Some power devices, work together will be hot, if the touch is cool, you can basically judge it did not work up. But if the hot place is not hot or the hot place is too hot, it is not enough.
General power transistor, regulator chip, etc., work in the following 70 degrees is completely no problem. 70 degrees is probably a concept? If you hand pressure up, you can adhere to more than three seconds, it means that the temperature is about 70 degrees below (pay attention to the first tentative to touch, do not burn your hands).