one. Light source part:

(1) Fault: The tungsten lamp is not lit;
Reason: The tungsten filament is blown (the highest probability of this cause);
Check: There is working voltage at both ends of the tungsten lamp, but the lamp is not bright; remove the tungsten lamp and use the multimeter resistance file to detect.
Disposal: Replace the new tungsten lamp;
(2) Fault: The tungsten lamp is not lit;
Reason: There is no lighting voltage;
Check: the fuse is blown;
Disposal: Replace the fuse (if the battery is replaced after replacement, check the power supply circuit);
(3) Fault: the xenon lamp is not lit;
Reason: The life of the xenon lamp has expired (the highest probability of such a cause);
Check: filament voltage, anode voltage, the filament may not be broken (can see the filament is red);
Disposal: replace the xenon lamp;
(4) Fault: The xenon lamp is not lit;
Cause: The xenon lamp is faulty;
Check: During the process of illuminating the xenon lamp, the filament is usually preheated for a few seconds, then the lamp can be ignited between the anode and the cathode. If the lamp flashes or flashes continuously in the beginning of the priming After moving, and after replacing the new xenon lamp, it is still possible that the starting circuit is faulty, and the high power transistor for lamp current adjustment has the greatest chance of damage.
Disposal: requires professional repair;
two. Signal part:
(1) Fault: no detection signal output;
Cause: No light beam is shining into the sample chamber;
Check: set the wavelength to 530nm, the slit should be opened to the widest position as much as possible, and in a dark environment, use a piece of white paper to be placed at the exit of the light window of the sample chamber to observe whether there is a green spot image on the white paper;
Disposal: Check if the light source mirror is turned to the position? Is the cutting motor of the two-beam instrument rotated (the ear can hear the sound of the motor rotating)?
(2) Fault: When there is no item in the sample chamber, the baseline noise is large in the full wavelength range;
Cause: The position of the light source mirror is incorrect, and the surface of the quartz window is sputtered with the sample;
Check: Is the light source illuminated to the center of the entrance slit? Are there any contaminants on the quartz window?
Disposal: readjust the position of the light source mirror and clean the quartz window with ethanol;
(3) Fault: In the absence of any items in the sample chamber, only the baseline noise in the ultraviolet region is large;
Cause: The aging of the xenon lamp, the deterioration of the mirror surface of the optical system, and the appearance of crystals in the filter;
Check: the baseline of the visible area is relatively flat. After the power is turned off, the monochromator and the upper cover of the instrument are opened. The naked eye can observe the grating and the surface of the mirror is covered with a white mist. If the optical system is normal, the maximum possibility is The aging of the xenon lamp can be judged by energy inspection or replacement of new lamps;
Disposal: Replace the xenon lamp, use the fire cotton glue to remove the dirt on the mirror surface or grind the filter with abrasive paste (Note: This technique requires some maintenance experience to implement);
(4) Fault: After the sample chamber is placed in the blank, the baseline memory is made, and the noise is large, especially in the ultraviolet region;
Cause: The surface or inner wall of the cuvette is contaminated, and the absorption of the UV spectrum by the glass cuvette or blank sample is too strong, making the amplifier out of the calibration range;
Check: set the wavelength to 250nm, first zero in the state without any items, then insert the empty cuvette into the side of the sample path, then the absorbance should be less than 0.07Abs; if it is greater than this value, it may be The color dish is not clean or a glass cuvette is used; the same method can also determine the amount of light absorption of the blank solution;
Disposal: Wash the cuvette and replace the blank solution;
(5) Fault: The absorbance value results in a negative value (most common);
Reason: No blank memory is used, and the absorbance of the sample is smaller than the blank reference solution;
Check: change the reference liquid and sample liquid to know the position;
Disposal: make blank memory, change reference solution or configure sample solution with reference solution;
(6) Fault: the sample signal has poor reproducibility;
Reason: Excluding the reason of the instrument itself, the biggest possibility is the unevenness of the sample solution; in the simple single-beam instrument, the sample cell holder is generally push-pull, and sometimes the repeated push-pull is not in the same position;
Check: Replace a stable sample judgment;
Disposal: take the correct sample configuration means; repair the positioning bead of the push-pull sample holder;
(7) Fault: When doing a baseline scan or a sample scan, the baseline or signal has a large negative pulse;
Cause: The scanning speed is set too fast. When the signal is read, the switching of the filter or the light source mirror is mistakenly read as a signal;
Check: change the scanning speed;
(8) Fault: When doing a baseline scan or a sample scan, the baseline or signal has a negative value for a long period of time or a large screen full noise;
Reason: The filter feed motor “out of step” causes the gear position to be misaligned, especially for domestic motors;
Check: It is possible to reply after rebooting, or turn on the relative position of the monochromator control wavelength and the filter (note: protect the detector from strong light when opening the monochromator);
Disposal: Replace the feeding machine motor;
(9) Fault: The peak position of the sample is incorrect;
Cause: The wavelength drive mechanism produces displacement;
Check: Determine whether the wavelength is accurate by the characteristic line of 656.1nm of the xenon lamp;
Disposal: For high-end instruments, the processing method is relatively simple, and the automatic correction function inherent to the instrument can be used; for relatively simple instruments, this adjustment requires professionals to perform;
(10) Fault: The resolution of the signal is not enough. The specific performance is: small peaks that should be superimposed on a large peak cannot be observed;
Cause: The slit setting is too narrow and the scanning speed is too fast, causing the detector response speed to keep up, thus losing the signal to be measured; according to common sense, a certain slit width should correspond to a certain range of scanning speed; or slit setting Too wide, the resolution of the instrument is reduced, and the small peak is merged into the big peak.
Check: slow down the scanning speed to see or narrow the slit;
Disposal: Fitting the scanning speed, the slit width, and the time constant into an optimized condition;
(11) Fault: When the wavelength of the instrument is fixed at a certain wavelength, the light absorption value signal swings up and down, especially the simple mode in which the measurement mode is converted into a key switch type;
Cause: The contact of the switch contact is poor due to long-term oxidation;
Check: When the key is pressed by hand, the absorbance value changes accordingly;
Disposal: Wash the button contacts with a metal activator;
(12) Fault: The zero point of the instrument is erratic, mainly reflected in the simple instrument;
Reason: In a simple instrument, the zero point is often adjusted by a potentiometer. This potentiometer is generally made of carbon film resistors. When used for a long time, it often causes poor contact;
Disposal: replace the potentiometer;