Advantech motherboards – a common maintenance method for industrial motherboards

1. Cleaning method

Use a brush to gently scrub dust off the motherboard. In addition, some of the cards and chips on the motherboard are in the form of pins, which are often poorly contacted due to pin oxidation. Remove the oxide layer from the surface with an eraser and reinsert it

2。 Observation method: Repeatedly check whether the plug and socket of the board to be repaired are skewed, whether the resistors and capacitor pins collide, whether the surface is burned, whether the chip surface is cracked, and whether the copper foil of the motherboard is burned. Also check for foreign objects falling between the motherboard components. If in doubt, it can be measured with a multimeter. Touch the surface of some chips. If the temperature is very high, try replacing the chip

3。 Resistance and voltage measurement method: In order to prevent accidents, the power supply above the motherboard (GND) is measured at +5V and ground after power is applied. The easiest way to do this is to measure the resistance between the chip's power supply pins and ground. When the power plug is not plugged in, the resistance is generally 300Ω, and the minimum is not less than 100Ω. Measure the reverse resistance again, there is a slight difference, but the difference should not be too large. If the forward and reverse resistance is very small or close to on, it indicates a short circuit and should be checked for the causes of this phenomenon:

(1) There is a disconnected chip on the system board. In general, this kind of fault is difficult to troubleshoot. For example, if the +5V of TTL chips (LS series) are connected together, the solder above the +5V pin can be sucked, levitated, and measured one by one to find the faulty chip. If the thread cutting method is adopted, it will affect the service life of the motherboard.

(2) There are damaged resistors and capacitors on the circuit board.

(3) There are conductive debris on the plate. After short-circuit troubleshooting, plug in all IO cards and measure whether +5V and +12V are short-circuited to ground. In particular, whether the +12V collides with the surrounding signal. When you have a good motherboard of the same model on hand, you can also measure the suspicious points on the motherboard by measuring the resistance value. By comparison, you can quickly spot chip failures

When the above steps don't work, you can plug in a power source for power-on measurements. +5V and +12V supplies are typically measured. When it is found that the voltage value deviates too far from the standard, the voltage can be measured again by separating the method, cutting some wires, or unplugging some chips. When the wire is cut or the chip is unplugged, if the voltage becomes normal, the component from which the wire or chip was unplugged is faulty

4。 There are many reasons for the failure of the plug-in switching host system, such as the failure of the motherboard itself or the failure of various plug-in cards on the IO bus, which may lead to the abnormal operation of the system. Using the plug-in maintenance method is an easy way to identify motherboard or IO device failures. This method is to turn off and unplug the plug-in boards one by one. Every time you pull out the circuit board, start the machine and observe the running status of the machine. Once a board is removed, the motherboard is operating normally, and the cause of the failure is the failure of the plug-in board or the corresponding IO bus slot and load circuit. If the system boots abnormally after unplugging all plug-in boards, the fault may occur on the motherboard. In essence, the switching method is to exchange the plug-in board of the same model, the plug-in board of the same bus mode, the plug-in board of the same function or the chip of the same model with each other, and judge the fault according to the change of the fault phenomenon. This method is mainly used in maintenance environments where plugging is easy, such as memory self-test errors. The same memory chip or memory module can be replaced to determine the cause of the failure

5。 Static-dynamic measurement analysis methods

(1) Static measurement method: suspend the motherboard in a close-up state, measure the level of the relevant points with a multimeter or logic pen according to the circuit logic principle or the logical relationship between the chip output and the input, and analyze and judge the cause of the fault (2) Dynamic measurement and analysis method: prepare a special judgment program or manually set the normal conditions, measure and observe the waveform of the relevant components with an oscilloscope during the operation of the machine, and compare it with the normal waveform to judge the fault location.

6. The judgment method is from simple to complex, and then combined with the principle of combination

With the wide application of large-scale integrated circuits, the logic correctness of the controller on the motherboard is becoming more and more difficult to judge by measurement with the improvement of system logic integration. First, the chips and resistor-capacitance components with simple logical relationships are judged, and then the faults are concentrated on the LSI chips with difficult logical relationships

7。 Software diagnostic methods

With random diagnostics, the principle of the program test method is to send data and commands with software, read the state of the line and the state of the chip (e.g., registers) to identify the location of the fault. This method is commonly used to check for various interface circuit faults and various circuits with address parameters. However, the premise of this method is that the CPU and the basic bus are functioning properly, that the relevant diagnostic software can be run, that the diagnostic card installed on the IO bus slot can be run, etc. Diagnostics should be rigorous, comprehensive, targeted, and able to show a certain pattern of signals for certain key components, repeat tests for unexpected failures, and display and record errors.

Advantech motherboards – a common maintenance method for industrial motherboards

Advantech motherboards – a common maintenance method for industrial motherboards

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