The complaint for this macro mp712s 17-inch monitor has happened. Once the lid was removed and the power, he felt a soft chip-chip noise, the power to try to come, but something had to close. no LED indicator light. As another monitor problems troubleshooting, the first thing I do is look for any burnt mark, connecting cables loose, dry joints and burned components. True enough, there was a crystalclearly marked burned in the middle of the motherboard.
Close inspection showed that it was a FET with the part number IRF630 (n-channel FET) and is located in the S-correction circuit. Looking at the FET from behind the 3 main board that a joint clean cut. I think this is the reason for the FET burned. Usually when you connect a component that had found dry, it is very likely that you'll be dry joints in other areas. The scan found all along the linea large number of joints in a dry circuit and the most obvious was the area immediately after the secondary side power switching transformer.
Verification of the flyback internal capacitor, transistor output horizontal (HOT) and the surrounding components fet burned has not been possible to find bad parts, so that after replacing the FET power has been turned on. Now the monitor to boot, but without high voltage and I could smell something burning at the circuit B +area. monitor was rapidly switched off and unplugged from the AC plug. With my finger on the B + fet heatsink was very hot and it is not normal. Because of this, I suspect the B + fet have also developed a short circuit. Upon check in, so the B + fet was so bad. The part number is B + fet IRF634A and also with a new replacement monitor is still denied to the tension is high.
The only choice I have is to do a stress test or measuringwith power. Placing the black meter probe to the soil cool and the red test in B + pin of the flyback and power, there was tension on the pin. This indicates that the work of B + circuit and the error might be elsewhere. Since the flyback transformer primary winding and capacitor internal controls is fine, the only suspect in the horizontal driver circuit.
To use the oscilloscope to monitor this waveform at the base ofThe heat, I chose the option to measure the horizontal transformer driver. Placing the red probe to the supply line, as shown in the figure and the black probe on the ground with cool power, I noticed there was an unusual number registered with the meter reading. E 'was only about 4 to 5 volts (where it should have at least 12 volts) and pulse (the meter pointer moves up and down). This is the meaning we seek. From here we could take our time to concentrate on finding the realcauses.
Using analog meter set to Ohms X1 where the black probe on the supply line and the red probe to the ground cold, it should show a low reading ohms, but in this case the needle at the top (low ohm reading). Component should be short-circuited, causing a short circuit to the meter reading recorded. Tracing along the supply line to the horizontal driver transformer adjacent components found a shorted driver transistor Q401 to the horizontal part number 2N7000. Normallymonitor, engineers prefer to use a bipolar transistor as the transistor compares to the horizontal driver FET. A new FET closed to repair the macro view mp712s 17 "monitor.
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