Comments on: Understanding The TV Horizontal Output Stage

By: Jestine Yong

Jestine Yong — Wed, 30 May 2012 00:36:46 +0000

HI Patterson,

Have you check the dc supply to the main power supply power ic? Certain power supply use optoisolator ic and the cpu will send a signal to the optoisolator ic either when the remote control is pressed or the tv front power button is pressed in order to fully turn on the main power supply. If there is a missing signal or the cpu is bad then check the optoisolator ic area or replace the cpu.

Jestine

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By: Patterson

Patterson — Wed, 30 May 2012 00:02:03 +0000

hi Jestine. Could you kindly give me some technical know how to troubleshoot & repair my tv?
well the problem is;
1. when I switch ON only the red LED indicator comes ON but no sign of raster, hissing sound or any of that sort. I tried replacing the switching IC, tested diodes in the power ckt, caps & resitors but to no avail.
Please I need your expect advice on this. The TV is a 29" Canca brand.
Thank you

Regards
Patterson

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By: admin

admin — Sat, 23 Apr 2011 14:10:43 +0000

Hi Chris,

Then you need to check the VGA cable signal wire to see if it broken internally. Without the horizontal and vertical signal to the mainboard the OSD will send out a NO signal symptom. Check also the mainboard to see if the line from the h/v signal to the MCU/SCALAR IC to see if there is any component shorted. A shorted component also could cause such symptom. Lastly if all checked to be good then either the MCU or the scalar IC is the fault.

Jestine

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By: chris

chris — Sat, 23 Apr 2011 01:05:33 +0000

HI Jestine

yes everytime i connect it i keep on getting no signal. tried different wires as well. i can`t understand what is the error!!

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By: admin

admin — Fri, 22 Apr 2011 17:19:55 +0000

Hi Chris,

You mean the OSD show no incoming signal eventhough you have connected the VGA cable?

Jestine

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By: chris

chris — Fri, 22 Apr 2011 04:54:00 +0000

Hi
first of all i would like to thank you for the good advice you gave me to repair the benq monitor 🙂 now i got a new strange problem. i got a daewoo monitor L520b which displays no signal all the time. i tried it with 3 different full working computers ,all the time same msg!!!what can be the cause pls? sorry for posting in this section but could not fing an open thread about this issue. thanks in advance

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By: chamarasuper

chamarasuper — Sat, 22 May 2010 23:23:56 +0000

Hi, Jestine. Thanks for the provided info. I was looking for right this information.

Thanks again.

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By: admin

admin — Tue, 02 Mar 2010 00:42:23 +0000

HI Damdin,

Well, it can be the horizontal deflection or the internal capacitor shorted inside flyback transformer. Please visit this link:

http://www.electronicrepairguide.com/testing-flyback-transformer.html

Jestine

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By: Damdin

Damdin — Sat, 27 Feb 2010 19:57:40 +0000

DAEWOO-726 BF deflection IC is STV9118.

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By: Damdin

Damdin — Sat, 27 Feb 2010 19:45:44 +0000

It's me again, Jestine. I would like to ask a question.

I have a DAEWOO-726BF CRT monitor.

1. When I press POWER switch after 3-6 seconds POWER LED will lit green one time and goes out. I think it's some kind of signal expressing some error. I searched thoroughly the web but couldn't find what that means.

2. Then I press the POWER switch again the green led will lit on all times but no raster, no high voltage. I hear only relay sound /possibly degauss circuit/, no static, no hissing. I checked all the secondary outputs from SMPS and they seem to me normal.

When I check the HOT only 60-70V on the collector pin, other pins have no voltage. I suspect the deflection IC is bad. It's VCC pin has 11.9V on it, but H-OUT pin has about 11V and no sawtooth impulse.

My question is these impulses /which will turn on the HOT/ are generated only in this IC or somewhere else, maybe some transistor? I have no direct replace part so I'm trying to dig deeper in surrounding parts. I checked almost every caps, even ceramic ones, diodes.

Now what should I do? Please, tell me?

Thanks in advance.

Best wishes!

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