1. Fault symptom:
In the case of normal startup or sometimes during scanning, all the monitors on the scanning rack are turned off, and only a few decimal points are green (just like the display that is turned off normally). And there are good and bad machines. When there is a problem, turn it off and then turn it on again, which will report that the scanning hardware system failed to initialize. Check the error record. The reported error is that the computer (OBC) on the rotating rack cannot be initialized, and the host cannot establish communication with the OBC within 10 seconds.
2. Diagnosis and elimination:
The software of CT/i equipment has strong monitoring and diagnosis functions, and the diagnosis accuracy is quite high. For the problem of displaying LAN errors, we must first understand the transmission path between the host and the LAN. The host establishes communication with the computer (STC) that scans the fixed part of the rack on the rack through the local network. Then, network communication is established between the communication board (SCOM) of sTC and the communication board (RCOM) of OBC. In this way, the host can send instructions and receive information to the computer (OBC) on the turntable through the local area network.
It must be pointed out that SCOM and RCOM consist of two 75? Coaxial cable is connected to the low-voltage slip ring system, and there are two buffer plates and two terminal plates on the slip ring to participate in information transmission. Therefore, it is judged that the fault may be caused by the network communication between STC and OBC.
We use the bypass method to check, that is, we use two coaxial cables to connect the cable J 1 output by STC with the cable J2 input by OBC, and connect the cable J2 output by STC with the cable J 1 input by OBC, so that the slip ring part can be temporarily abandoned. Turn on the 1 10 v AC and 550 V DC power switches (be sure to keep the shaft drive switch off, otherwise it will be dangerous), the host sends an initialization command, and the hardware is initialized successfully. At the same time, the monitoring program reported an error: the shaft drive switch was not turned on, which is normal. All the displays on the scanning frame are normal and kept all the time, indicating that the host computer has good communication with STC and OBC networks. But also reflects that the fault lies in the slip ring system. To this end, we carefully cleaned six signal slip rings and carbon brushes with gauze. Turn the slip ring and use a multimeter to confirm that the carbon brush is in good contact with the slip ring. After debugging, the fault still exists. However, when checking the fault, it is found that the fault is related to the temperature. When the temperature is low, the machine can resume working for a while, while when the temperature is high, it can't work at all.
We analyze four metal plates on the slip ring. There is a problem with the 12 v power supply, but this problem has been eliminated through inspection and board replacement. Finally, the fault is concentrated on the slip ring. We repeatedly checked the input and output points of the slip ring with a multimeter, and found that the signal output point J4 of the rotating buffer plate was not connected with the slip ring. We removed the circuit board and found that the external terminal of signal slip ring 2 was in poor contact with the slip ring. After replacing the slip ring, the fault was completely eliminated.