Question about ViewSonic E70f 17" CRT Monitor

5 Answers

Horizontal output transistor keeps failing

I have this 17" viewsonic and finally it fails, i check inside and found the horizontal output transistor BU4522AX fails, i've replaced it three times but keeps failing. dc voltages seems to be normal. please help me.

Posted by Anonymous on

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  • Anonymous May 15, 2007

    i hav fixed the two, output transisitor and a shorted switch mosfet but there is still no picture that seems like the switching circuit is not working, i never change the IC yet. the LED changes from orange to green but there was no high voltage or horizontal out. i out of my wit right now on this. You may help me.

  • prashantmane May 29, 2008

    Dear Sir,

    No display problem. I have VIEWSONIC VCDTS2183-1P (Optiquest Q41) model CRT monitor. BU2508 was short i replaced it with new one. After replacing then also there is no display on monitor. Please help me to solve this problem.

  • Anonymous Jun 07, 2008

    horizontal out transistor keeps failing on my 17" monitor

  • wildtaurus Aug 25, 2008

    hot keeps failing

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Anonymous

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The horizontal output transitor is always connected to the primary winding of the flyback transformer (via collector) and also to the horizontal deflection coil via an electrolytic capacitor. The most likely suspect for damaging the transistor is the fylback transformer. In some countries there are electronic stores that test flyback transformer by winding a few turns on the ferrite core and applying a test voltage. This test will only test the secondary. The primary winding is difficult to test for turn to turn short because the resistance is quite low and you do not know the 'good' resistance.

Posted on May 16, 2007

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What do u mean by LOT ( EHT ), in this problem, the main 200v supply intended for the horizontal output transistor wud passed thru a MOSFET, The gate was connected to the output of an IC that determines the presence of signal from a computer. The MOSFET would reduce this voltage to 165v for the hor transistor. now the presence of signal from computer would change the LED from orange to green, but the 200V did not passed to the hor transistor, the MOSFET was not turned on. One thing i've noticed was if i remove the hor out transistor, the MOSFET would turn on. This MOSFET will reduce the 200v to 165v so i could not try shorting it when the hor out transistor is soldered. i've already change shorted 0.22mf capacitor in the flyback transformer that i thought was the cause and the 2.2uf/50v capacitor blown before. please explain to me what u mean LOT.

Posted on May 20, 2007

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My tv is daewo 29 inch. help me what kind of horizontal out we are to replace cause its always damage in minutes.tyvm

Posted on Mar 10, 2009

Anonymous

Replaced your horizontal output transistor D5072 and this solve your problem.

Posted on Jan 28, 2008

Anonymous

Replace the LOT (eht) transformer and than put the new horizantal transistor than switch on and monitor will b displays ok

Posted on May 20, 2007

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Check and replace damaged component/s at its horizontal scan output section circuit. Check the LOT (Line Output Transformer) too for damage. Replace the horizontal scan output transistor. Check the input voltage to LOT. If the voltage is absent check the feeder resistor; if any. If you wish to get some details; check the site linked here. Viewing it in "Mosaic" or "Magazine" will make surf easy. Surf the site with patience. Pull up older posts.
http://electronicshelponline.blogspot.com/
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1 Answer

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Hello
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Flyback links 
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Warning; the number of suppliers for CRT monitor parts is shrinking rapidly, my best supplier, ICM in California is long gone. 

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