Analysis and Treatment of Failure of X-ray 3370E X-ray Fluorescence Spectrometer
The 3370EX Fluorescence Spectrometer is a product of Nippon Scientific Co., Ltd. in the late 1980s. It is mainly used to analyze the chemical composition of steel, alloys, various mineral products, slag, chemical products, food, agricultural products, biological and environmental protection samples. Our institute introduced this instrument in 1989 and it has been used for more than 10 years. In the course of its operation, some failures have occurred in succession. Several examples of circuit failures and their handling methods are described below:
1 High voltage generator failure
1.1 Fault phenomenon
According to the normal procedure, the instrument is turned on. When the X-ray tube high voltage is gradually increased, the instrument emits a “beep†sound. At the same time, the voltmeter and the current representation of the control panel of the high-voltage generator are all zero, and the X-ray lamp is off. The high voltage generator does not have a high voltage output.
1.2 Failure Analysis
Turn off the high voltage generator power supply and the instrument's main power supply immediately. Open the high-voltage generator control box, visual inspection found that the main circuit fuse F1 burned out, testing to determine the open fuse. The working principle of the main circuit of the high-voltage generator is that the output voltage level can be adjusted by changing the conduction angle of the thyristor K1 and K2, and the step-up process must be carried out step by step. Analysis of the causes of fuse over-current protection actions include:
a) Error in the control letter error code output by the control circuit, causing the thyristor to suddenly turn on completely;
b) Control of sudden short-circuit damage of silicon, similar to sudden full turn-on;
c) The internal components of the high voltage generator are damaged and a short circuit occurs;
d) The X-ray tube is broken and a short circuit occurs.
After inspection and test, the signal output by the control circuit is correct, the thyristor K1 and K2 are intact, the X-ray tube is intact, and no abnormality is found at the input end of the high-voltage transformer box. There should be a problem inside the high-voltage transformer box.
1.3 Troubleshooting
Inside the high-voltage transformer box is a high-voltage transformer, high-voltage rectifying and filtering electrical appliances, filament power supply and measuring circuit, etc. that are immersed in the high-voltage transformer oil.
First remove the high-voltage cables, power lines and control lines, remove the high-voltage transformer box from the instrument; then open the cover, remove the high-voltage transformer and rectifier filter circuit; wait until the oil drains slightly, check the devices one by one, find the high-voltage filter capacitor short circuit. The cause of the fault is the damage of the high voltage capacitor. Replace the new high-voltage capacitor, restore the rectifier filter circuit and the high-voltage transformer box, put it back in the instrument, connect the connection cable, and replace it with a new fuse F1. The inspection is confirmed to be correct. Turn on the power supply of the instrument and the power supply of the high voltage generator. Set the high voltage step by step. The voltmeter indicates the correct value. The high voltage generator is repaired and the instrument returns to normal operation.
It should be pointed out that special attention should be paid in this maintenance work: (1) After turning off the power supply, when disassembling the high voltage generator, it is necessary to wait for a period of time to allow the high voltage circuit to fully discharge to ensure safety; (2) The performance of the transformer needs to be performed. The test must be replaced if it fails; (3) The high voltage transformer and the rectifier filter circuit should be put back into the oil slowly. Avoid air bubbles and reduce the insulation of the oil.
2 Cleaning F-PC Counter Center Wire Failure
2.1 Fault phenomenon
The F-PC counter center wire cleaning process is: When the F-PC counter center is cleaned, the instrument issues an alarm message: There is no cleaning current. Then PAH (Pulse Height Analyzer) adjustment, F-PC counter no count. Check the F-PC counter and found that the center filament burned severely.
2.2 Failure Analysis
The F-PC counter center wire cleaning process is: F-PC counter rotates to cleaning position, the center wire enters the cleaning circuit through the contacts, automatically controls the cleaning current, and maintains a certain time, so that the center wire is heated to a higher level Temperature, burning off the surface of the pollutants, to achieve the purpose of cleaning. According to the original analysis of the F-PC counter center wire cleaning circuit, the cause of the center wire failure may be:
a) The current limiting resistor R is damaged;
b) The cleaning voltage is too high;
c) Problems with the time control circuit and the power-on time is too long.
Since the center filament burns out due to overcurrent, it tends to cause a and b. Actual detection; current limiting resistor R, cleaning voltage, and time control circuit are all normal. Then, a dynamic check was performed to measure the resistance of the contact point to 0 Ω when the center wire was turned to the cleaning position. If the rated cleaning voltage is added at this time, the center wire will inevitably cause the overcurrent to burn off; while the current limiting resistor R will not pass the current, so the instrument alarms that “there is no cleaning current.†The inspection found that the contact piece of the cleaning position is loose, when the counter touches When the head is pressed down, it is short-circuited with the wall of the dichroic chamber, causing a burning failure. Fasten the contact piece, replace the center piece, and install the F-PC counter. Check the machine, the instrument's F-PC counter center wire automatic cleaning function is normal.
3 heating circuit failure
3.1 Fault phenomenon
When the instrument is turned on normally, data abnormality is found during normalization, and the temperature of the instrument shell is lower than usual. Check the heating circuit section and find that the heater is not heated and the fan is not turned.
3.2 Failure Analysis
The internal temperature of the instrument is controlled at 37±1°C and its heating circuit principle. The voltage between the detection points is 200V AC (the power of the instrument is Japanese standard). At this time, the fan does not turn, and the fan should be bad. Observe that the heating indicator lamp D is bright, indicating that there is a heating signal. The voltage between the detection points is 200V AC, indicating that the driving part is working properly. Further find out that the temperature fuse RT is open and the heater is intact. Analysis believes that: due to long-term operation, the fan is damaged, causing the heater to overheat, so that the temperature protection resistor RT action, disconnect the heating circuit, stop the heater work.
3.3 Troubleshooting
Replace the fan with a new temperature protection resistor. Reboot, fan and heater are working properly.
4 vacuum detection circuit failure
4.1 Fault phenomenon
The correct degree of boot, because the analysis chamber vacuum is always stable at a certain value, can not reach the required value, the instrument stagnates in the self-test vacuum pumping state, can not enter the normal working state.
4.2 Failure Analysis and Processing
First of all, check the seal of each joint of the vacuum system and there is no problem. Second, check the vacuum detection circuit. Using the same characteristics of the vacuum detection circuit of the analysis chamber and the sample chamber, the vacuum detection circuit and the detector are exchanged for inspection. When the same state is found, the analysis chamber vacuum and the measurement output from the detection circuit are low. Therefore, without knowing the circuit parameters, the voltage and electrical parameters of the circuit are tested in a segmented manner using the contrast method. Finally, the problem points are found and the device with poor performance is detected: the electrolytic capacitor. Because of its reduced insulation, the leakage increases, causing the potential at this point to be low, resulting in a lower vacuum measurement than the actual value. After the replacement of the device, the power-on self-test passed smoothly and the instrument returned to normal operation.
1 High voltage generator failure
1.1 Fault phenomenon
According to the normal procedure, the instrument is turned on. When the X-ray tube high voltage is gradually increased, the instrument emits a “beep†sound. At the same time, the voltmeter and the current representation of the control panel of the high-voltage generator are all zero, and the X-ray lamp is off. The high voltage generator does not have a high voltage output.
1.2 Failure Analysis
Turn off the high voltage generator power supply and the instrument's main power supply immediately. Open the high-voltage generator control box, visual inspection found that the main circuit fuse F1 burned out, testing to determine the open fuse. The working principle of the main circuit of the high-voltage generator is that the output voltage level can be adjusted by changing the conduction angle of the thyristor K1 and K2, and the step-up process must be carried out step by step. Analysis of the causes of fuse over-current protection actions include:
a) Error in the control letter error code output by the control circuit, causing the thyristor to suddenly turn on completely;
b) Control of sudden short-circuit damage of silicon, similar to sudden full turn-on;
c) The internal components of the high voltage generator are damaged and a short circuit occurs;
d) The X-ray tube is broken and a short circuit occurs.
After inspection and test, the signal output by the control circuit is correct, the thyristor K1 and K2 are intact, the X-ray tube is intact, and no abnormality is found at the input end of the high-voltage transformer box. There should be a problem inside the high-voltage transformer box.
1.3 Troubleshooting
Inside the high-voltage transformer box is a high-voltage transformer, high-voltage rectifying and filtering electrical appliances, filament power supply and measuring circuit, etc. that are immersed in the high-voltage transformer oil.
First remove the high-voltage cables, power lines and control lines, remove the high-voltage transformer box from the instrument; then open the cover, remove the high-voltage transformer and rectifier filter circuit; wait until the oil drains slightly, check the devices one by one, find the high-voltage filter capacitor short circuit. The cause of the fault is the damage of the high voltage capacitor. Replace the new high-voltage capacitor, restore the rectifier filter circuit and the high-voltage transformer box, put it back in the instrument, connect the connection cable, and replace it with a new fuse F1. The inspection is confirmed to be correct. Turn on the power supply of the instrument and the power supply of the high voltage generator. Set the high voltage step by step. The voltmeter indicates the correct value. The high voltage generator is repaired and the instrument returns to normal operation.
It should be pointed out that special attention should be paid in this maintenance work: (1) After turning off the power supply, when disassembling the high voltage generator, it is necessary to wait for a period of time to allow the high voltage circuit to fully discharge to ensure safety; (2) The performance of the transformer needs to be performed. The test must be replaced if it fails; (3) The high voltage transformer and the rectifier filter circuit should be put back into the oil slowly. Avoid air bubbles and reduce the insulation of the oil.
2 Cleaning F-PC Counter Center Wire Failure
2.1 Fault phenomenon
The F-PC counter center wire cleaning process is: When the F-PC counter center is cleaned, the instrument issues an alarm message: There is no cleaning current. Then PAH (Pulse Height Analyzer) adjustment, F-PC counter no count. Check the F-PC counter and found that the center filament burned severely.
2.2 Failure Analysis
The F-PC counter center wire cleaning process is: F-PC counter rotates to cleaning position, the center wire enters the cleaning circuit through the contacts, automatically controls the cleaning current, and maintains a certain time, so that the center wire is heated to a higher level Temperature, burning off the surface of the pollutants, to achieve the purpose of cleaning. According to the original analysis of the F-PC counter center wire cleaning circuit, the cause of the center wire failure may be:
a) The current limiting resistor R is damaged;
b) The cleaning voltage is too high;
c) Problems with the time control circuit and the power-on time is too long.
Since the center filament burns out due to overcurrent, it tends to cause a and b. Actual detection; current limiting resistor R, cleaning voltage, and time control circuit are all normal. Then, a dynamic check was performed to measure the resistance of the contact point to 0 Ω when the center wire was turned to the cleaning position. If the rated cleaning voltage is added at this time, the center wire will inevitably cause the overcurrent to burn off; while the current limiting resistor R will not pass the current, so the instrument alarms that “there is no cleaning current.†The inspection found that the contact piece of the cleaning position is loose, when the counter touches When the head is pressed down, it is short-circuited with the wall of the dichroic chamber, causing a burning failure. Fasten the contact piece, replace the center piece, and install the F-PC counter. Check the machine, the instrument's F-PC counter center wire automatic cleaning function is normal.
3 heating circuit failure
3.1 Fault phenomenon
When the instrument is turned on normally, data abnormality is found during normalization, and the temperature of the instrument shell is lower than usual. Check the heating circuit section and find that the heater is not heated and the fan is not turned.
3.2 Failure Analysis
The internal temperature of the instrument is controlled at 37±1°C and its heating circuit principle. The voltage between the detection points is 200V AC (the power of the instrument is Japanese standard). At this time, the fan does not turn, and the fan should be bad. Observe that the heating indicator lamp D is bright, indicating that there is a heating signal. The voltage between the detection points is 200V AC, indicating that the driving part is working properly. Further find out that the temperature fuse RT is open and the heater is intact. Analysis believes that: due to long-term operation, the fan is damaged, causing the heater to overheat, so that the temperature protection resistor RT action, disconnect the heating circuit, stop the heater work.
3.3 Troubleshooting
Replace the fan with a new temperature protection resistor. Reboot, fan and heater are working properly.
4 vacuum detection circuit failure
4.1 Fault phenomenon
The correct degree of boot, because the analysis chamber vacuum is always stable at a certain value, can not reach the required value, the instrument stagnates in the self-test vacuum pumping state, can not enter the normal working state.
4.2 Failure Analysis and Processing
First of all, check the seal of each joint of the vacuum system and there is no problem. Second, check the vacuum detection circuit. Using the same characteristics of the vacuum detection circuit of the analysis chamber and the sample chamber, the vacuum detection circuit and the detector are exchanged for inspection. When the same state is found, the analysis chamber vacuum and the measurement output from the detection circuit are low. Therefore, without knowing the circuit parameters, the voltage and electrical parameters of the circuit are tested in a segmented manner using the contrast method. Finally, the problem points are found and the device with poor performance is detected: the electrolytic capacitor. Because of its reduced insulation, the leakage increases, causing the potential at this point to be low, resulting in a lower vacuum measurement than the actual value. After the replacement of the device, the power-on self-test passed smoothly and the instrument returned to normal operation.
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