How To Restore LG 710E CRT Monitor With Energy Blink Drawback
How To Restore LG 710E CRT Monitor With Energy Blink Drawback
LG 710E 17" CRT Monitor got here in with the grievance of energy blink. An influence blink drawback can be trigger by either in primary or secondary section or even in both sections.
A defective energy IC, energy fet breakdown when below load, high esr in electrolytic capacitor, increased in present sense resistor worth, a shorted zener diode, a leaky transistor, open circuit or resistor has modified value in main facet could 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 etc may cause energy to blink as well.
Normally what I do is to take away the B+ fet first and connect a lightweight bulb to tell apart whether or not is the primary or after the B+ circuit elements that brought about energy to blink. Nevertheless in this case, I did not put the light bulb and I immediately eliminated the B+ fet and power on the monitor. For your info, this B+ fet is the N-channel mosfet and this B+ fet is part of the increase circuit.
After removing the B+ fet, not only the facility didn't blink, there was show as well and the anode voltage reads about 12 Kilo volt (a good monitor should have about 24 KV). The rationale why you got 12 kilo volts is as a result of the enhance circuit just isn't functioning due to the removal of the B+ fet. The display proven a small width and the horizontal size control is already set to the utmost (you may't get most width as a result of the anode voltage is just 12 KV). You'll be able to control or set every thing in the On Screen Show (OSD) besides you possibly can't convey horizontal size to maximum.
With having a display, it's a good clue to me as a result of I knew that many circuits is working resembling power part (so you don't suspect main side anymore), flyback transformer, yoke coils, micro-p, eeprom, horizontal and vertical circuit, colour circuit and even the Osd circuit. With out the B+ fet, there's show but with B+ fet the power blink. On this case, one would at all times test the B+ fet first am I right? However the B+ fet turned out to be good!
Now the place is the offender hiding? Troubleshooting typically can be very pissed off and most of the time is at all times fun. One among my strategies that I favored to use is to the touch for any unusually scorching components on board with my finger. (Please take note for all digital repairers-switch off and unplug the ability cable and discharge the massive filter capacitor in primary aspect before you start to touch any parts).
Normally after energy off, I would touch on the flyback first then to different parts surrounding the excessive voltage section. While browsing the elements with my finger I stumbled upon a resin coated ceramic disc capacitor which is sort of hot. It is situated near the flyback transformer and in reality the capacitor was there is to behave as a filter capacitor for the four hundred vdc line output as proven from the photo.
After the cap was removed and checked with an analog meter, it confirmed a shorted studying even in the X1 ohms range. A good capacitor ought to show a charge and discharge activity in the X10 ok ohms range. A new capacitor substitute for this LG 710E 17" CRT Monitor cured the fault.
The rationale why the monitor power blinks is as a result of the defective capacitor develop into shorted when in full operating voltage (increase circuit is functioning and roughly 60 -70 vdc enter the B+ flyback pin).
When the B+ fet was eliminated (increase circuit not working and only about forty vdc enter the B+ pin of flyback) the monitor just isn't working underneath full working voltage and the defective capacitor can nonetheless tolerate (partial quick) and have become hot. I imagine if the monitor is switched "on" for a little bit longer, it would trigger the capacitor to develop a direct short circuit and if this happen, removing the B+ fet to check the monitor would not make any totally different (the ability would nonetheless blink).
A defective energy IC, energy fet breakdown when below load, high esr in electrolytic capacitor, increased in present sense resistor worth, a shorted zener diode, a leaky transistor, open circuit or resistor has modified value in main facet could 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 etc may cause energy to blink as well.
Normally what I do is to take away the B+ fet first and connect a lightweight bulb to tell apart whether or not is the primary or after the B+ circuit elements that brought about energy to blink. Nevertheless in this case, I did not put the light bulb and I immediately eliminated the B+ fet and power on the monitor. For your info, this B+ fet is the N-channel mosfet and this B+ fet is part of the increase circuit.
After removing the B+ fet, not only the facility didn't blink, there was show as well and the anode voltage reads about 12 Kilo volt (a good monitor should have about 24 KV). The rationale why you got 12 kilo volts is as a result of the enhance circuit just isn't functioning due to the removal of the B+ fet. The display proven a small width and the horizontal size control is already set to the utmost (you may't get most width as a result of the anode voltage is just 12 KV). You'll be able to control or set every thing in the On Screen Show (OSD) besides you possibly can't convey horizontal size to maximum.
With having a display, it's a good clue to me as a result of I knew that many circuits is working resembling power part (so you don't suspect main side anymore), flyback transformer, yoke coils, micro-p, eeprom, horizontal and vertical circuit, colour circuit and even the Osd circuit. With out the B+ fet, there's show but with B+ fet the power blink. On this case, one would at all times test the B+ fet first am I right? However the B+ fet turned out to be good!
Now the place is the offender hiding? Troubleshooting typically can be very pissed off and most of the time is at all times fun. One among my strategies that I favored to use is to the touch for any unusually scorching components on board with my finger. (Please take note for all digital repairers-switch off and unplug the ability cable and discharge the massive filter capacitor in primary aspect before you start to touch any parts).
Normally after energy off, I would touch on the flyback first then to different parts surrounding the excessive voltage section. While browsing the elements with my finger I stumbled upon a resin coated ceramic disc capacitor which is sort of hot. It is situated near the flyback transformer and in reality the capacitor was there is to behave as a filter capacitor for the four hundred vdc line output as proven from the photo.
After the cap was removed and checked with an analog meter, it confirmed a shorted studying even in the X1 ohms range. A good capacitor ought to show a charge and discharge activity in the X10 ok ohms range. A new capacitor substitute for this LG 710E 17" CRT Monitor cured the fault.
The rationale why the monitor power blinks is as a result of the defective capacitor develop into shorted when in full operating voltage (increase circuit is functioning and roughly 60 -70 vdc enter the B+ flyback pin).
When the B+ fet was eliminated (increase circuit not working and only about forty vdc enter the B+ pin of flyback) the monitor just isn't working underneath full working voltage and the defective capacitor can nonetheless tolerate (partial quick) and have become hot. I imagine if the monitor is switched "on" for a little bit longer, it would trigger the capacitor to develop a direct short circuit and if this happen, removing the B+ fet to check the monitor would not make any totally different (the ability would nonetheless blink).
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