Circuit in the daily maintenance work, how to accurately judge the quality of the circuit in the power supply IC chip, maintenance is important content of TV, audio, video equipment, if the judgment is not accurate, not only spend a lot of energy, the key is the integrated circuit fault still exist, so the correct judgment of integrated circuit, is a compulsory course for each of the maintenance personnel.
One, board check method:
1. Observation method: whether burn, burn off, blister, plate surface broken line, socket corrosion.
2. Meter measurement: +5V, GND resistance is too small (less than 50 ohms).
3. Power check: for clear broken plate, the voltage of 0.5-1V can be adjusted slightly. After starting, the IC on the hand washboard can be used to make the chip in question heat up, so as to sense.
4. Logic pen check: check whether the signals are strong or weak at each end of the key suspected IC input, output and control poles.
5. Identify main working areas: most boards have clear division of labor, such as: control area (CPU), clock area (crystal vibration) (frequency), background picture area, action area (role, aircraft), sound production and synthesis area, etc. This is very important for the in-depth maintenance of the computer board.
Two, troubleshooting method:
1 will doubt the chip, according to the manual instructions, first check the input, output whether there is a signal (waveform), and then check the IC control signal (clock), etc., if the IC has no control signal, track its front pole, until find the damaged IC.
2. Don't take the same model from the extreme for now. Or the IC of the same program content on the back, boot observation is better, to confirm whether THE IC is damaged.
3. Through the tangent and jumper to find a short line: found part of the line and ground, +5V or other IC should not be connected to the foot short circuit, can cut off the line measurement, judge is IC problem or plate line problem, or from other IC borrowed signal welding to waveform error IC to see whether the phenomenon is better, judge the quality of IC.
4. Control method: find a good computer board with the same content, measure the corresponding IC pin wave type and its number, confirm whether IC is damaged.
Three, chip disassembly method:
1. Cutting foot method: does not hurt the board, can not be reused.
2. Drag tin method: solder on both sides of IC feet, drag back and forth with high temperature soldering iron, and start IC(easy to damage the board, but can save the test IC).
3. Barbecue method: barbecue in alcohol lamp, gas stove, electric stove, etc., and then start IC after the tin melts on the board (not easy to master).
4. Tin pot method: Make a special tin pot on an electric stove. After the tin is dissolved, the IC to be removed from the plate is immersed in the tin pot, and the IC can be started without hurting the plate, but the equipment is not easy to manufacture.
5. Electric air gun: use special electric air gun to unload the piece, blow the IC pin part to be unloaded can start the IC after the tin (pay attention to shaking the air gun when blowing the board, otherwise the computer board will bubble, but the cost of the air gun is high, generally about 2000 yuan).