Fault repair of electronic ballast

- Jan 11, 2019-

1. The most fluorescent lamp failure is that the lamp is not lit, the lamp does not have any reaction. First, measure whether the R0 is burned. RO itself is an insurance function, once the overcurrent will burn, so as not to damage more components. Some ballasts are connected to the 0.5A insurance tube at Ro.

If Ro burns, there will be a stream. Fault. Replace the R05 inch in a disconnect, with the pointer multimeter rx10k to measure the resistance at both ends of the municipal lead should be more than 2Mf (R1+R2 series value); The same should be the case for the pen test. If two, the Rectifier Bridge has diode burnout, if less than 2MD2, then C1, C2 leakage, if this resistance value meets a requirement, can be added to the test a,b two points should be about 300V DC voltage. But sometimes a power is burned to break Ro, which is a short-circuit diode in the Rectifier bridge, should be one side d1-d4 of the positive and negative resistance. Rectifier diode damage probability is very small, and filter capacitance damage more, C1 and C2 series use, will cause a chain reaction, a capacitor breakdown, the other is also damaged. When replacing, it is best to choose a voltage-resistant 300V capacitor. 

2. After determining that the rectifier filter circuit is good, then proceed to check the subsequent circuit. Because a is disconnected, use the multimeter rx10k to measure the resistance between a,b two points (Red Stylus B, black pen connection a), this value should be greater than 500kSZ. If it is 00, it should be checked whether the C-e pole of R10,VT2 is burned; if it is around 470kn, then in the VT2 of the C-E pole serious leakage, or even short circuit, here to raise a problem prone to miscalculation, when the resistance between the a,b only about 30KF, as if it is VT2 leakage, it is not,

Because with the 1OKS2 block measurement, the 9V voltage in the table is added to the a,b, to the VT2 injection of people deflection, VT2 in the state of the guide, so the resistance between the C-E is small, not leakage. 

3. After determining that the resistance between the a,b is correct, use the multimeter rxlk to measure the two PN junction resistors of Vtl and VT2, and roughly judge the performance of these two transistor. It should be noted that when measuring the PN junction resistance of VT1, it is necessary to disconnect the R5 in order to obtain the correct reading. The resistance values of R5 to 1110 are measured with RXL, and these resistors have examples of burnout. Burning 119,1110 is more common, these two resistors use too long resistance values will increase, as long as their value is greater than 2dZ, the circuit is not easy to vibrate, the lamp is not bright, should focus on inspection.

As for D5, D6, C4 pressure resistance is high, magnetic ring transformer TRL winding line diameter is thick, insulation is good, these can not be damaged. 

4. After the above static measurement, check the fault element, restore the circuit, carefully check the circuit board of the solder joints and components have no short circuit, touch, loose, broken place.

After the correction of the correct power, in most cases, the fluorescent lamp can return to normal work, but there may be the following failure, should be excluded one by one. (1) There is still a stream, continue to burn ro, which is mainly VT1 or VT2 c-e between the pressure of a f drop, there is a high pressure soft breakdown, must choose enough pressure-resistant transistor replacement.

In addition, C3 or C5 pressure is not enough, with a multimeter to check out, it is best to weld with a 500V shaker to measure its insulation resistance should be o0, otherwise considered leakage. (2) The two ends of the lamp redness, the brightness is obviously insufficient. At this time, the first use of the multimeter AC block voltage at both ends of the lamp, should be about 100V. This is only a reference value, not an actual number, because the voltage waveform at both ends of the lamp is not a standard sine wave, and the frequency is above 20kHz, more than the frequency response range of the multipurpose table. If this voltage is less than 100V, it may be that the performance of VT1 or VT2 is reduced and the conductivity is insufficient.

Without oscilloscopes, the b-e voltage of two tubes measured with a digital multimeter is about 0.4V, and if the deviation is too large or even positive, it shows that the pipe is not in the saturated conduction state, it is advisable to change the pipe test, do not blindly adjust the circuit. If the lamp end pressure has reached 100V, still luminous abnormal, it is the lamp performance is poor. Usually determine the fluorescent lamp tube good or bad, only to measure its filament resistance, if the filament is not broken, there is no large area of black tube, it is considered intact.

However, poor quality lamp although its filament is not broken, there is no trace of blackening in the tube, but it can not be used normally. (3) The lamp brightness is insufficient, the tube has a spiral aperture, which is flowing through the lamp small current, the main reason is that the capacity of the C5 drop too much, you may wish to C5 at both ends and pick up a 2.2nf1630v capacitor to try. In various grades of electronic ballast, the resonant capacitor C5 capacity is not the same, roughly between 3-10nf. Its capacity is too large or too small will make the lamp can not shine properly.