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Industrial circuit board repair skills
Don’t rely too much on online testers
. Functional testing cannot replace parameter testing
. Functional testing can only test the cut-off area of the device, amplification area and saturation area, but it is impossible to know the working frequency and speed at this time.
. For digital chips, we only know the output changes of high and low levels, but we cannot detect the changing speed of its rising and falling edges.
. For analog chips, it deals with simulated changes. It is intricately affected by the distribution of circuit components and different signal solutions. With the current online testing technology, it is impossible to solve the online testing of analog chips. Therefore, the results of this functional test are for reference only.
. Most online test programs will give a pass or fail test after functional testing of various chips on the circuit board. So why doesn't it tell whether there is a problem with the device under test? This is the shortcoming of this type of tester. Because there are too many factors that are affected (interference) during online testing. It is required to take many measures before testing (such as disconnecting the crystal oscillator, removing the chip with the program, adding isolation interrupt signals, etc.). Whether this is effective is worth studying. At least, current test results are sometimes unsatisfactory.
. Readers who know about online testers all know this jargon. A chip that fails the online test is not necessarily damaged, and a chip that passes the test must not be damaged. Its explanation is that if the device is affected by online effects or resists interference, the result may not pass, which is not difficult to understand. So, will damaged chips fail when tested? The answer is indeed not definite. The author and colleagues have all encountered that the chip is obviously damaged (to be precise, the board will not work if this chip is replaced), but the test result is passed. The authoritative explanation is that this is caused by the working principle of the tester itself (rear drive technology). Therefore, we cannot rely too much on the function of online testers (despite the mysterious propaganda of various manufacturers), otherwise the work of repairing circuit boards will go astray.
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In the next step, in accordance with the unified arrangements and requirements of the Party Central Committee and the State Council, the Ministry of Industry and Information Technology will unswervingly promote supply-side structural reform, accelerate the conversion of new and old driving forces, take more effective measures, strive to maintain stable industrial growth, and ensure Achieve various goals and tasks throughout the year.
Wen Ku, Director of the Information and Communications Development Department of the Ministry of Industry and Information Technology, and Huang Libin, Deputy Director of the Operation Monitoring and Coordination Bureau of the Ministry of Industry and Information Technology attended the press conference and answered reporters' questions.
The momentum of industrial stabilization has increased
Zhang Feng pointed out that in the first three quarters of this year, the added value of industries above designated size increased year-on-year, with increases of ., . and . in the first, second and third quarters respectively. The added value of the manufacturing industry increased year-on-year. There is an industry in each major industrial category that has accelerated year-on-year growth, and there is a province in the country where the industrial growth rate is faster than the national average.
In the past month, the main business income of industrial enterprises above designated size increased year-on-year, and profits increased year-on-year. Among them, manufacturing profits increased year-on-year, reversing the situation of continuous negative growth in corporate profits since last year. The central government has introduced a series of measures to reduce the institutional transaction costs of enterprises and have shown effective results. In the previous month, the cost per 100 yuan of main business income of industrial enterprises above designated size fell by . yuan year-on-year, and the corresponding main business income profit margin increased by .
At present, there are more and more positive signals in the economic operation. In March, the industrial producer price index increased year-on-year. This was the first time since March that it returned to the positive growth range. Business inventories have experienced negative growth in recent months after zero year-on-year growth in the previous month. Since March, the manufacturing purchasing managers' index has basically been above the boom and bust line, and has rebounded to ., which is the highest monthly value since March. Some physical quantity indicators improved.
The initial results of making up for shortcomings and cutting overcapacity in the industrial sector are beginning to show. Since the beginning of this year, investment in industrial technological transformation has increased by about 1% year-on-year. Driven by investment in technological transformation and other factors, the added value of the equipment manufacturing industry in the first three quarters grew at a rate of... New breakthroughs have been made in the independent research and development of a number of major equipment such as the country's first large-diameter polyethylene centrifuge equipment. Industries such as food, industrial textiles, and sports utility vehicles that are in line with the upgrading direction of consumer demand and led by brands are operating well. The work of cutting overcapacity is advancing in an orderly manner, and the steel industry has completed the cumulative work in the first three quarters
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