The Importance Of High Voltage Probe 


A high-voltage probe is the tool needed to check the high voltage at the anode of the crt. It can also be use to measure the focus voltage of  the flyback transformer. It can measure the high voltage up to 45kv and more. Most of the normal multimeter can only measure voltage up to 1000 volt-so please don't use it to check the high voltage otherwise the meter may get spoilt! To make the measurement, just connect the ground cable of the probe to the chassis of the computer monitor or tv. Then, slip the probe tip underneath the flyback anode cap. The voltage can be read on the face of the meter. The high voltage probe that i have is made in  Japan under the brand name Kaise-Sk9000. It's very reliable and worth

the investment.


In monitor troubleshooting i don't use it regularly. I only use it when there is a complaint of high voltage shutdown, focus problem, small and big horizontal width. Using just the high voltage probe i can tell which section is having problem. This save me a lot of time because i have eliminated the guessing game! With the probe you could see if the monitor shutdown before it reach 24kv or after 24kv. Assuming it shutdown when the voltage touched 15kv then you have to check the horizontal oscillator section because there is no horizontal drive pulse when it reached 15kv. In one case i found a resistor became high ohm that was located near the horizontal oscillator circuit. If the high voltage shutdown when it touches the 28-30kv scale then you have to suspect b+ voltage could be too high, internal flyback transformer capacitance value became low or open, open in safety capacitor (holddown capacitor) and circuit related to feedback and flyback transformer.


If the display width is small and only measured 15-18kv then suspect problem in the b+ fet circuit. It could be a missing gate pulse to the b+ fet, open filter capacitor, current sense resistor that connect to the source pin of b+ fet value run, a defective b+ coil and b+ fet and etc. A small width also can be cause by a defective in the horizontal size and s-correction circuit. The different is the high voltage still remain 24 kv! Thus using the high voltage probe i can easily tell which circuit that i should check and this will speed up my repair.


Another useful feature of the high voltage probe is that you can measure the focus voltage to see if the focus problem in the display are cause by a defective picture tube, flyback transformer or other circuit. Suspect flyback transformer if the voltage that you measured increasing after sometimes. By right the focus voltage should remain steady or constant regardless of time.


Conclusion, if you are in the monitor or tv business and still haven't invest in the high voltage probe-i strongly you to do so as it is one of the testing equipment that can make your troubleshooting easier and faster.


Author By : Jestine Yong



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1 Feb 2007

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