If the cable TV amplifier and optical receiver do not use a switching power supply, then it uses a series step-down power supply with a transformer step-down. The circuit has a voltage regulator integrated block 7824. The discrete component amplifier is also useful for 7812. According to the author's overhaul of more than 1500 fault amplifier statistics, 7824 damage accounted for about 6% of the fault, which is relatively easy to damage components.
The method for detecting whether the voltage regulator integrated block 7824 is damaged is: the amplifier is not connected to the power supply, and the cover is opened, and the multimeter can be directly measured by the R×1 file on the 7824, and the middle pen is first connected with the red pen, and the black pen is respectively connected to the two outer legs. The result of the two measurements should not move the pointer of the multimeter, indicating that the resistance is infinite; if the hands are deflected, the 7824 is broken. Then connect the black pen of the multimeter to the middle leg, and the red pen is connected to the other two legs respectively. The measurement result of the multimeter should be about 1/3 to 1/2 of the surface scale of the deflection surface; if there is one time the needle will not deflect, or there is When the hands are fully biased and the 0 resistance is displayed, the 7824 is broken. In most cases, this judgment is accurate. Only a few cases are short-circuited by short-circuiting other parts of the circuit near 7824. It is necessary to weld and test again.
After the above method is used to determine that the 7824 is broken, the circuit board is removed, and the 7824 is soldered. The same method is used to measure again, and the judgment method is the same. The diagnosis of 7824 is broken, you can replace it with a new 7824. After you put it in, don't forget to screw its heat sink to the amplifier housing. Then use your finger to press on the plastic case of the 7824 integrated block, and conduct the power test. If you feel that the 7824 is hot and hot (short-time test, generally no problem), immediately turn off the power, then remove the amplifier module and try again, if not hot. Hot, it means that the amplifier module is shorted and replaced.
If it is detected that the voltage regulator integrated block is good, the amplification module is most likely to be damaged and can be replaced. If it still doesn't work, check the 7824 three pins for desoldering. The 7824 three-pin desoldering rate is about 1.5% of the fault amplifier. Check for re-welding.
When the voltage regulator integrated block is normal, the online voltage after the power is turned on is as shown.
If the cable TV amplifier and optical receiver do not use a switching power supply, then it uses a series step-down power supply with a transformer step-down. The circuit has a voltage regulator integrated block 7824. The discrete component amplifier is also useful for 7812. According to the author's overhaul of more than 1500 fault amplifier statistics, 7824 damage accounted for about 6% of the fault, which is relatively easy to damage components.
The method for detecting whether the voltage regulator integrated block 7824 is damaged is: the amplifier is not connected to the power supply, and the cover is opened, and the multimeter can be directly measured by the R×1 file on the 7824, and the middle pen is first connected with the red pen, and the black pen is respectively connected to the two outer legs. The result of the two measurements should not move the pointer of the multimeter, indicating that the resistance is infinite; if the hands are deflected, the 7824 is broken. Then connect the black pen of the multimeter to the middle leg, and the red pen is connected to the other two legs respectively. The measurement result of the multimeter should be about 1/3 to 1/2 of the surface scale of the deflection surface; if there is one time the needle will not deflect, or there is When the hands are fully biased and the 0 resistance is displayed, the 7824 is broken. In most cases, this judgment is accurate. Only a few cases are short-circuited by short-circuiting other parts of the circuit near 7824. It is necessary to weld and test again.
After the above method is used to determine that the 7824 is broken, the circuit board is removed, and the 7824 is soldered. The same method is used to measure again, and the judgment method is the same. The diagnosis of 7824 is broken, you can replace it with a new 7824. After you put it in, don't forget to screw its heat sink to the amplifier housing. Then use your finger to press on the plastic case of the 7824 integrated block, and conduct the power test. If you feel that the 7824 is hot and hot (short-time test, generally no problem), immediately turn off the power, then remove the amplifier module and try again, if not hot. Hot, it means that the amplifier module is shorted and replaced.
If it is detected that the voltage regulator integrated block is good, the amplification module is most likely to be damaged and can be replaced. If it still doesn't work, check the 7824 three pins for desoldering. The 7824 three-pin desoldering rate is about 1.5% of the fault amplifier. Check for re-welding.
When the voltage regulator integrated block is normal, the online voltage after the power is turned on is as shown.
If the cable TV amplifier and optical receiver do not use a switching power supply, then it uses a series step-down power supply with a transformer step-down. The circuit has a voltage regulator integrated block 7824. The discrete component amplifier is also useful for 7812. According to the author's overhaul of more than 1500 fault amplifier statistics, 7824 damage accounted for about 6% of the fault, which is relatively easy to damage components.
The method for detecting whether the voltage regulator integrated block 7824 is damaged is: the amplifier is not connected to the power supply, and the cover is opened, and the multimeter can be directly measured by the R×1 file on the 7824, and the middle pen is first connected with the red pen, and the black pen is respectively connected to the two outer legs. The result of the two measurements should not move the pointer of the multimeter, indicating that the resistance is infinite; if the hands are deflected, the 7824 is broken. Then connect the black pen of the multimeter to the middle leg, and the red pen is connected to the other two legs respectively. The measurement result of the multimeter should be about 1/3 to 1/2 of the surface scale of the deflection surface; if there is one time the needle will not deflect, or there is When the hands are fully biased and the 0 resistance is displayed, the 7824 is broken. In most cases, this judgment is accurate. Only a few cases are short-circuited by short-circuiting other parts of the circuit near 7824. It is necessary to weld and test again.
After the above method is used to determine that the 7824 is broken, the circuit board is removed, and the 7824 is soldered. The same method is used to measure again, and the judgment method is the same. The diagnosis of 7824 is broken, you can replace it with a new 7824. After you put it in, don't forget to screw its heat sink to the amplifier housing. Then use your finger to press on the plastic case of the 7824 integrated block, and conduct the power test. If you feel that the 7824 is hot and hot (short-time test, generally no problem), immediately turn off the power, then remove the amplifier module and try again, if not hot. Hot, it means that the amplifier module is shorted and replaced.
If it is detected that the voltage regulator integrated block is good, the amplification module is most likely to be damaged and can be replaced. If it still doesn't work, check the 7824 three pins for desoldering. The 7824 three-pin desoldering rate is about 1.5% of the fault amplifier. Check for re-welding.
When the voltage regulator integrated block is normal, the online voltage after the power is turned on is as shown.
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