Weak current College】 【monitor debug and repair methods】.

Specific about the display of some of the common fault of debugging, maintenance methods:
1. how to repair the display switching power supply.
Today's computer monitor power supplies in the vast majority are stabilized power supply [switching power supplies]. The so-called switching power supply, the switching power supply adjustment work on deadline and saturated zone. It is due, rather mechanical switch 's, saturated, the equivalent of a mechanical switch closure. The role of starting switch transistor, called switch tube [switch adjustment tube, transistor's a], switch tube to stable voltage of power supply, we'll call it switching power supplies. Monitor out of a large portion of failure are switching power supply's fault, it was a play that as long as the master switch of the power supply of the repair method, you can return to repair the display.
Stabilized power supply with old-fashioned linear series regulator, it has a small power consumption, high efficiency, voltage range, * safety, do not have large power transformers, filter capacitance, low temperature rise inside. By switching power supplies and loads of join mode, switch the power supply can be divided into series and shunt two categories. Series switching power supply's output through switch adjustment tube and rectifier diodes and power grid directly linked, so the whole bottom is charged, commonly known as ' hot plate ', to repair a security problem, we at the time, attention should be paid to the player. Series switching power supply's excellent Office is on the circuit, switch required simple adjustment pipes require less. But parallel switching power supply, its output and AC 220V power by switching transformer side, to isolate the secondary side, so the whole circuit board in addition to switch a transformer side of connected parts, the other places are not charged, so called "cold plate". Parallel switching power supply security is good, but its relatively complex, on the circuit switching valve's demanding, such as its strong protection circuit work, that the poor state of failure are more serious. If you press different incentive to Division is divided into his Flyback and self-excited two categories.
Above we monitor switching power supply with some understanding, due to the maintenance of switching power supplies is the monitor maintenance most key [in daily maintenance in the amount you want to share a monitor maintenance of 70%] and difficulties. Here we have to switch power supply of the repair of sense to do a larger system.
In the maintenance of switching power supply's sometimes better to join an isolation transformer. What is isolating transformers? which means in the switching power supply side and the secondary side pressure ratio 1: 1 power transformer, it can avoid public areas causing electric shock power. For 14 inch to 17-inch monitor with 70W-100W of isolating transformer is enough. Isolation transformers can purchase can also be made. Self-made isolating transformers for General requirements for its power, is greater than the machine's 20%-40% can be. For the isolation transformer 100W available old power transformer-will the other side pulled out, and then rewinds isolation layer [to ensure isolation good], and then with 1 mm wire number as in the original hoop to bypass system again.
In the maintenance of switching power supply's sometimes also can buck repair method. Its approach is the monitor's power plug, then during an AC transformer, then turn the AC regulator's output voltage to 100V, then power on maintenance and successive increases power supply voltage to repair it.
A. fault burn-on both a, insurance, the output voltage is zero. This is normally provided by switch tube is breakdown, C, E very short circuit. At this point to switch to the tube and remove the logs its C, E and resistance, such as zero or very small, then change it to. But they also want to check other components have no problem just after power on.
B. failure to appear ' S ' grating shape distortions. This issue should be focused on checking filter circuits and voltage circuit, usually diode has a circuit breaker, from full-wave rectification into half-wave rectification, or its filtering capacity.
C. failure three, AC 220V rectifier filter circuit, short circuit fault occurs and no fire insurance. You should check out if there is no short circuit diode rectifier, filter capacitors are serious leakage. Also you can pluck degaussing coils plug, check the degaussing thermistor for any short circuit fault, if any should be renewed.
D. failure to post without grating without display, the power led is not lit, but does not fire insurance. This problem should check Exchange mutual inductance transformer has no open circuit, circuit of current limiting resistors [normally 15-25W, 5-40 European cement resistors] there is no open [blow] failure, or if the circuit breaker rectifier diode.
E. failure, no raster, no display and built-in making unusual sounds. As a "Squeaky" sound, the oscillation frequency is low, you should check and oscillation related components, such as a "new" sound, power overcurrent protection, over-current protection circuit should be checked.
F. fault six, the output voltage is above or below normal value. Output voltage higher than normal, or low out ten volts to dozens of Volt, but is not zero, the protection circuit is not action [burn]. This symptom will vary according to the voltage change and varied. You can adjust the voltage adjustment potentiometer, such as output unchanged or changed very little, sampling error amplifier circuit failure, which provide a baseline of Zener diode breakdown or short circuit of a great possibility. Secondly, sampling amplifier transistor is damaged, you can create output voltage larger or smaller.
2. display tube high voltage spark of maintenance.
Chromogenic tube high voltage spark faults monitor repair one of the most common questions. Its mainly manifested in the screen grating appear many erratic highlights, serious time into dot line, sometimes you can hear the built-in "Squeak", if the brand impact of serious, will cause the display image fuzzy, and probably will result in a few seconds or several minutes after the disappearance of the symptoms of grating. While digital tube high voltage spark the reasons and more, the main parts are: picture tube, high voltage spark; picture tube high voltage or high pressure Cap fire mouth; high-voltage line-end brand impact package; focus potentiometer inside bad brand impact and so on. Here we separate mention its maintenance.
A. picture tube block, spark of maintenance.
Picture tube, spark general level in the focus. Produce picture tube, internal spark of due mainly to monitor use of the environment is too dampDo not wet or long term. Since the focus of the voltage level is very high in 4-9KV, repair methods is, turn off the power, pipe saddle from tail plate removed, use a knife or fine sandpaper will scrape pin of rust, and then clean with pure alcohol. And the inner wall of the pipe, plastic rust clean with alcohol, and then use the hair dryer, replace it. But now you should have a picture tube pipe, block sale, you could compare the old pipe, block to buy a new one. Note the PIN and Jack-off relationship, some pipe, block appearance to look exactly the same, but the pins and Jack is short, but the new socket is conduction, this will cause a short circuit, causing failure.
B. picture tube high-pressure nozzle or high pressure Cap around the fire.
Picture tube high voltage spark, around the mouth among environmental humidity, there is also explicit high-pressure nozzles and contacts between conical glass does not close or impurities are also relevant. To repair the high-pressure nozzle spark, served on their discharge, is a large wooden handle flat blade solution, insert multiple times in the high pressure nozzle touch can sometimes be heard ' pop ' acoustic. And then remove the high-pressure apparatus, check the high pressure nozzle and high voltage card spring there is no equivalent to their surrounding fire signs and ash. If Yes, you can take to clear the previous method, and then use the blower to clean it dry, it is necessary to pay attention to temperature and time in order to avoid explicit duct overheat and exploding. Then in high pressure nozzle around evenly coloured some arc ling, then fasten high pressure caps. High voltage apparatus in General also has sold very cheap, you can change it if necessary.
C. high voltage spark package and focus potentiometer.
High-voltage spark can cause package grating fuzzy or grating. If the package itself is high voltage spark, that only get a new one. If you are the leader in high pressure package, available-to-end brand impact its pure alcoholic liniment clean.
If you are focusing on high-voltage package in the brand, you can shutdown potentiometer adjusted focus potentiometer times and see if I can make it better internal contact contact. If not, it would be better to replace it.
3. how to monitor degauss.
The display is magnetized cant is commonly encountered problems. The main causes, monitor * be magnetized near magnetic materials; after moving the monitor so that the built-in deflection coil shift, producing color pure bad; degaussing circuit is damaged. Although some monitors itself with certain degauss feature, but for the more serious of the magnetization is some powerless.
For the external magnetic field interference caused by the colour purity, available external degaussing is degaussed. Eraser can purchase can also be made. Self-made eraser available industrial AC contactor removed after you connect the power cable to the side and switch into a plastic tube inside or around the electric blanket. In emergency situations, you can find a used electric meter [1-5A are available], remove the voltage coils, its ' doors '-shaped core remove, just put in the t-coil core and coil, and the two coil Terminal, connect the power cord and switch plug with plastic wrap it up. But whatever the degaussing method, it's important to be aware of security. After power constantly shaking hands Eraser, gradually * near screens, with magnetic parts can be repeated, and then while swaying Eraser side back to the screen 2 meters and then turn off the power. Each time you power on time should not be too long, if not a degaussing may well be repeated several times.
For as the result of moving the monitor color purity after bad, you can open the presentation for the rear cover to deflection coil back position and tighten the screws on the deflection yoke can be both. For built-in degauss circuit damage caused by a bad color purity, to check the thermal resistance [degaussing] damage, remove it, issued by hand as ' give ' voice is a thermistor is quenched. Multimeter for questioning their PIN resistance values, such as the resistance of less than 8 euro or greater than 50 euro the RTC components within the degaussing resistance is bad and should be renewed. If degaussing resistor, you should focus on checking degaussing coils of wire, plug, socket, there is no loose and between poor contact. In addition if degaussing resistance short or leakage also will result in the failure of the power-on fire insurance, we should pay attention.
4. display widescreen small failure of maintenance.
Monitor the use of a long period of time, it may appear the display area is larger or smaller. Then adjust the horizontal and vertical width potentiometer adjustment did not have the effect, you need to open the rear cover. For example, a 14-inch monitor is produced in Taiwan, with three years later, in the display mode screen 640X480 basically normal adjustable, but at 800 x 600 display mode serious small, each side has two cm black border around, and make adjustment knob outside the machine; is also true of more gas is 640X400 DOS mode and serious large screen, so that even in the startup splash screen can only see 2/3, adjustment knob also has no effect. Remove the display back cover, see their main circuit board four group fine-tuning potentiometer knob [namely H.WIDTH; PIN; V.HEIGHT; H.PHASE], 31KHz, 35KHz, 38KHz three synchronization potentiometer knob, and they are respectively responsible for 640X400, 640X480, 800X600 three display modes. Connect the monitor to turn the power on WINDOWS and DOS [640X400] three resolution mode, use a small knife, respectively, for regulating potentiometer knob to three resolution are satisfied. Because each monitor this several knobs similar, we can repeatedly try more times either. When finished, and then enter the appropriate resolution mode, and then adjust the brightness of focused and under to your own satisfaction, two knob General in high pressure on the package, we adjust time pay attention to safety, because of the high voltage is high on the package. On this kind of adjustment of the key is to an audacious. This method can also be purchased on some new hand-monitor, the resolution switching partial screen when you want to handle the situation.