How To Repair service LG 710E CRT Check With Electricity Blink Issue

LG 710E 17″ CRT Monitor arrived in with the grievance of electric power blink. A electrical power blink issue can be trigger by both in main or secondary section or even in both sections.

A faulty power IC, electrical power fet breakdown when less than load, substantial esr in electrolytic capacitor, enhanced in existing sense resistor price, a shorted zener diode, a leaky transistor, open up circuit or resistor has modified price in major aspect can cause ability to blink. As for the secondary aspect, a shorted secondary diode, flyback, Incredibly hot, horizontal yoke coil, damper diode, B+ fet, an open filter capacitor, shorted IC and and so on can induce electrical power to blink as perfectly.

Commonly what I do is to eliminate the B+ fet initially and join a gentle bulb to distinguish no matter whether is the main or following the B+ circuit parts that induced electricity to blink. Even so in this case, I did not place the light-weight bulb and I right removed the B+ fet and electrical power on the observe. For your details, this B+ fet is the N-channel mosfet and this B+ fet is section of the strengthen circuit.

Soon after removing the B+ fet, not only the electrical power did not blink, there was display screen as very well and the anode voltage reads about 12 Kilo volt (a very good monitor must have about 24 KV). The explanation why you obtained 12 kilo volts is for the reason that the increase circuit is not working because of to the removal of the B+ fet. The display shown a small width and the horizontal dimensions control is by now established to the utmost (you can not get highest width due to the fact the anode voltage is only 12 KV). You can command or set anything in the On Display screen Exhibit (OSD) apart from you cannot deliver horizontal sizing to utmost.

With getting a display screen, it is a very good clue to me since I realized that several circuits is functioning these as ability portion (so you really don’t suspect principal side any more), flyback transformer, yoke coils, micro-p, eeprom, horizontal and vertical circuit, coloration circuit and even the Osd circuit. Without having the B+ fet, there is show but with B+ fet the electricity blink. In this case, a person would usually verify the B+ fet initially am I correct? Even so the B+ fet turned out to be excellent!

Now in which is the offender hiding? Troubleshooting occasionally can be quite annoyed and most of the time is normally enjoyment. One of my solutions that I liked to use is to touch for any unusually hot elements on board with my finger. (Make sure you take take note for all digital repairers-switch off and unplug the electricity cable and discharge the large filter capacitor in principal side in advance of you start to contact any elements).

Typically after electric power off, I would contact on the flyback very first then to other components surrounding the superior voltage area. When browsing the parts with my finger I stumbled on a resin coated ceramic disc capacitor which is fairly very hot. It is positioned in close proximity to the flyback transformer and in actuality the capacitor was there is to act as a filter capacitor for the 400 vdc line output as demonstrated from the image.

Right after the cap was taken off and checked with an analog meter, it showed a shorted reading through even in the X1 ohms array. A excellent capacitor need to present a demand and discharge activity in the X10 k ohms selection. A new capacitor substitute for this LG 710E 17″ CRT Watch cured the fault.

The motive why the keep track of energy blinks is simply because the faulty capacitor develop into shorted when in comprehensive functioning voltage (enhance circuit is working and about 60 -70 vdc enter the B+ flyback pin).

When the B+ fet was removed (raise circuit not doing work and only about 40 vdc enter the B+ pin of flyback) the keep an eye on is not doing work under complete functioning voltage and the faulty capacitor can still tolerate (partial quick) and became warm. I believe if the keep track of is switched “on” for a tiny longer, it would lead to the capacitor to develop a immediate limited circuit and if this transpire, removing the B+ fet to examination the observe would not make any distinctive (the ability would continue to blink).