LG 710E CRT Monitor With Energy Blink Problem How To Repair?
LG 710E 17" CRT Monitor came in with the complaint of energy blink. An influence blink downside may be trigger by both in main or secondary section and even in each sections.
A defective power IC, energy fet breakdown when beneath load, excessive esr in electrolytic capacitor, increased in current sense resistor worth, a shorted zener diode, a leaky transistor, open circuit or resistor has modified value in major facet can cause power to blink. As for the secondary facet, a shorted secondary diode, flyback, HOT, horizontal yoke coil, damper diode, B+ fet, an open filter capacitor, shorted IC and and many others can cause power to blink as well.
Normally what I do is to remove the B+ fet first and connect a lightweight bulb to distinguish whether is the first or after the B+ circuit parts that induced power to blink. Nonetheless on this case, I didn't put the light bulb and I straight eliminated the B+ fet and power on the monitor. For your data, this B+ fet is the N-channel mosfet and this B+ fet is part of the increase circuit.
After eradicating the B+ fet, not only the power did not blink, there was show as properly and the anode voltage reads about 12 Kilo volt (a very good monitor ought to have about 24 KV). The rationale why you bought 12 kilo volts is as a result of the increase circuit just isn't functioning due to the removing of the B+ fet. The show shown a small width and the horizontal dimension control is already set to the utmost (you may't get most width as a result of the anode voltage is barely 12 KV). You can management or set all the things within the On Screen Show (OSD) besides you'll be able to't carry horizontal dimension to maximum.
With having a display, it is a good clue to me because I knew that many circuits is working similar to power section (so you do not suspect major side anymore), flyback transformer, yoke coils, micro-p, eeprom, horizontal and vertical circuit, color circuit and even the Osd circuit. With out the B+ fet, there is display however with B+ fet the facility blink. In this case, one would at all times check the B+ fet first am I right? Nonetheless the B+ fet turned out to be good!
Now the place is the culprit hiding? Troubleshooting typically could be very annoyed and most of the time is at all times fun. One in all my strategies that I preferred to use is to the touch for any unusually sizzling elements on board with my finger. (Please take word for all electronic repairers-swap off and unplug the power cable and discharge the large filter capacitor in primary side earlier than you begin to the touch any parts).
Normally after power off, I might touch on the flyback first then to different components surrounding the high voltage section. Whereas browsing the components with my finger I stumbled upon a resin coated ceramic disc capacitor which is quite hot. It's positioned close to the flyback transformer and in fact the capacitor was there is to behave as a filter capacitor for the 400 vdc line output as shown from the photo.
After the cap was eliminated and checked with an analog meter, it showed a shorted reading even within the X1 ohms range. A great capacitor should show a cost and discharge exercise in the X10 ok ohms range. A brand new capacitor substitute for this LG 710E 17" CRT Monitor cured the fault.
The explanation why the monitor power blinks is as a result of the defective capacitor turn out to be shorted when in full working voltage (enhance circuit is functioning and roughly 60 -70 vdc enter the B+ flyback pin).
When the B+ fet was eliminated (enhance circuit not working and solely about 40 vdc enter the B+ pin of flyback) the monitor just isn't working below full working voltage and the faulty capacitor can still tolerate (partial quick) and became hot. I imagine if the monitor is switched "on" for a little longer, it will trigger the capacitor to develop a direct quick circuit and if this happen, removing the B+ fet to test the monitor wouldn't make any different (the ability would nonetheless blink).
LG 710E CRT Monitor With Energy Blink Problem How To Repair?
LG 710E 17" CRT Monitor came in with the complaint of energy blink. An influence blink downside may be trigger by both in main or secondary section and even in each sections.
A defective power IC, energy fet breakdown when beneath load, excessive esr in electrolytic capacitor, increased in current sense resistor worth, a shorted zener diode, a leaky transistor, open circuit or resistor has modified value in major facet can cause power to blink. As for the secondary facet, a shorted secondary diode, flyback, HOT, horizontal yoke coil, damper diode, B+ fet, an open filter capacitor, shorted IC and and many others can cause power to blink as well.
Normally what I do is to remove the B+ fet first and connect a lightweight bulb to distinguish whether is the first or after the B+ circuit parts that induced power to blink. Nonetheless on this case, I didn't put the light bulb and I straight eliminated the B+ fet and power on the monitor. For your data, this B+ fet is the N-channel mosfet and this B+ fet is part of the increase circuit.
After eradicating the B+ fet, not only the power did not blink, there was show as properly and the anode voltage reads about 12 Kilo volt (a very good monitor ought to have about 24 KV). The rationale why you bought 12 kilo volts is as a result of the increase circuit just isn't functioning due to the removing of the B+ fet. The show shown a small width and the horizontal dimension control is already set to the utmost (you may't get most width as a result of the anode voltage is barely 12 KV). You can management or set all the things within the On Screen Show (OSD) besides you'll be able to't carry horizontal dimension to maximum.
With having a display, it is a good clue to me because I knew that many circuits is working similar to power section (so you do not suspect major side anymore), flyback transformer, yoke coils, micro-p, eeprom, horizontal and vertical circuit, color circuit and even the Osd circuit. With out the B+ fet, there is display however with B+ fet the facility blink. In this case, one would at all times check the B+ fet first am I right? Nonetheless the B+ fet turned out to be good!
Now the place is the culprit hiding? Troubleshooting typically could be very annoyed and most of the time is at all times fun. One in all my strategies that I preferred to use is to the touch for any unusually sizzling elements on board with my finger. (Please take word for all electronic repairers-swap off and unplug the power cable and discharge the large filter capacitor in primary side earlier than you begin to the touch any parts).
Normally after power off, I might touch on the flyback first then to different components surrounding the high voltage section. Whereas browsing the components with my finger I stumbled upon a resin coated ceramic disc capacitor which is quite hot. It's positioned close to the flyback transformer and in fact the capacitor was there is to behave as a filter capacitor for the 400 vdc line output as shown from the photo.
After the cap was eliminated and checked with an analog meter, it showed a shorted reading even within the X1 ohms range. A great capacitor should show a cost and discharge exercise in the X10 ok ohms range. A brand new capacitor substitute for this LG 710E 17" CRT Monitor cured the fault.
The explanation why the monitor power blinks is as a result of the defective capacitor turn out to be shorted when in full working voltage (enhance circuit is functioning and roughly 60 -70 vdc enter the B+ flyback pin).
When the B+ fet was eliminated (enhance circuit not working and solely about 40 vdc enter the B+ pin of flyback) the monitor just isn't working below full working voltage and the faulty capacitor can still tolerate (partial quick) and became hot. I imagine if the monitor is switched "on" for a little longer, it will trigger the capacitor to develop a direct quick circuit and if this happen, removing the B+ fet to test the monitor wouldn't make any different (the ability would nonetheless blink).
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