34T776636G01 TOSHIBA 电路板

34T776636G01 reset circuit
1. When there is a large scale integrated circuit on the circuit board to be repaired, attention should be paid to the reset problem.
2. Before testing, it’s best to put it back on the equipment, turn it on and off repeatedly, and press the reset key several times.
34T776636G01 Function and Parameter Test
Portable microscope for circuit board inspection
Portable microscope for circuit board inspection
1. < tester > can only reflect the cut-off area, amplification area and saturation area when testing the device, but can’t measure the specific values such as working frequency and speed.
2. Similarly, for TTL digital chips, we can only know that there are high and low level output changes, but there is no way to find out the speed of its rising and falling edges.
34T776636G01 crystal oscillator
1. Usually, it can only be tested by oscilloscope (crystal oscillator needs to be powered on) or frequency meter, and multimeter can’t measure it, otherwise, substitution method can only be adopted.
2. Common failures of crystal oscillator are: A. Internal leakage, B. Internal open circuit, C. Deterioration frequency offset, D. External capacitance leakage. The leakage phenomenon here can be detected by the VI curve of < tester >.
3. Two judgment methods can be used in the whole board test: A. The relevant chips around the crystal oscillator failed during the test; B. No other fault points were found except the crystal oscillator.
Portable microscope detection circuit board
Portable microscope detection circuit board
4. There are two kinds of crystal oscillators: A. Two-legged, B. Four-legged, of which the second one is powered on, so be careful not to short-circuit at will. V. Distribution of fault phenomena 1. Incomplete statistics of circuit board fault parts: 1) 30% chip damage, 2) 30% discrete component damage,
3) 30% of the wiring (PCB coated with copper wire) is broken, and 4) 10% of the program is damaged or lost (there is an upward trend).
2. As can be seen from the above, when the circuit board to be repaired has wiring and program problems, and there is no good board, it is neither familiar with its wiring nor the original program can be found. It is unlikely that this board will be repaired.