Common repair process
1. Routine inspection: First of all, visually inspect the hash board to be repaired to observe whether there is any displacement, deformation, or scorching of the small heat sink? If any, you must deal with it first; if the small heat sink is displaced, remove it first, wash off the original glue, and re-adhesive after the repair is passed.
Secondly, after the visual inspection is no problem, the impedance of each voltage domain can be tested first to detect whether there is a short circuit or an open circuit. If found, it must be dealt with first.
Thirdly, check whether the voltage of each voltage domain reaches 0.8V, and the voltage difference of each voltage domain shall not exceed 0.05V. If the voltage of a certain voltage domain is too high or too low, the circuits in the adjacent voltage domain generally have abnormal phenomena. Need to investigate the reason first.
2. After the routine test is no problem (the short-circuit test of the general routine test is necessary to avoid the chip or other materials being burnt due to the short circuit when the power is turned on), the chip test can be performed with the test fixture, and the judgment and positioning can be made according to the test result of the test fixture.
3. According to the test result displayed by the test fixture, start near the faulty chip and check the chip test points (CLK IN OUT/TX IN OUT/RX IN OUT/B IN OUT/RST IN-OUT) and voltages such as VDD, VDD0V8, VDD1V8, etc..
4. According to the signal flow, except for the RX signal, the signal is transmitted in the reverse direction (72 to chip 1), and several signals CLK CO BO RST are transmitted in the forward direction (1-72), and the abnormal fault point is found through the power supply sequence.
5. When locating the faulty chip, the chip needs to be melt-soldered again. The method is to add flux around the chip (preferably no-clean flux), heat the solder joints of the chip pins to a dissolved state, move gently up and down, left and right, and press the chip; make the chip pins and the pads Re-bond and close the tin. In order to achieve the effect of tinning again.
If the fault remains the same after re-soldering, you can directly replace the chip.
6. The repaired hash board must be tested more than twice when testing. Two test times before and after: the first time, after the replacement of parts is completed, the hash board needs to be cooled down and then tested. After passing, put it aside. For the second time, after a few minutes wait for the hash board to cool down completely, perform the test again. Although the time for the two tests is a few minutes, this does not affect the work. Put the repaired board aside, continue to repair the second board, wait for the second board to be repaired and set aside to cool down, and then test the first board. In this way, the time is just staggered, and the total time is not delayed.
7. The repaired board. It is necessary to classify the faults and make records of the type, location, reason, etc. of the replacement components. To prepare for feedback back to production, after-sales, and R&D
8.After finishing the recording, install the whole machine and wait for the running test.