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Electronic Repair Questions/Answers & Testimonials Part 7

By on July 27, 2008

I’ve encounter another usual problem which has to do with 14″ television circuit.my question is,if the main fuse on the circuit board system is breaking regularly,what is the common fault.I’m normally successful by replacing the main F.E.T on the primary side of the power supply system of the board. However i just need further diagnosis and other courses of such fault.

Hi G,

Check the bridge rectifier and directly replace the Posistor and also make sure the fuse is slow blow (same or higher ampere) and not fast blow.

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Hi Jestine,

Good day.

I would like to ask help. I encountered a monitor with a low brightness. I tried to twist the screen adjustment located at the flyback and the brightness adjustment at the front panel of the monitor but it didn’t work. And, there is also a monitor wherein I can’t adjust the horizontal size although I have cleaned the microswitches.

Hi N,
Try check the heater voltage and make sure it has 6.3 volt dc. If the g2 and the heater voltage check to be okay then chances the picture have problem and need replacement. As for the screen size problem, check the surrounding components in the pincushion transistor area. This transistor usually located near flyback and attached to heatsink and the part number are d669a, b649a, d2012, d2058 and etc. Hope this helps!

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Hi,

I like to test the smd capacitors, the very small ones near crystal on the mainboard of tft monitor. In your ebook i read : it should not show any reading, but when i measure with multimeter on 10k ohm setting the meter is showing 0 ohms. It is with all capacitors i try to measure , so i think i`m doing something wrong.

Hi S,
You have to remove the capacitor from the board in order to do the testing otherwise the result would be 0 ohm.

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Hi Jestine Yong,

Thank you for answering my questions, you are too good to be true , I experienced such good help & prompt response to my electronic quotation . Ones again thanks for help me.

Regards,

Samadhan

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Dear Sir,

Sir one of my friend LCD monitor has a problem when i start the pc just display on and immediately goes off, please help me what can i do?

Hi S,

It is in the inverter area and could be fault cause by shorted transistors, dry joints, open tuning capacitors or even bad backlight.

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Hi Jestine,

Thanks for a wonderful book of yours. I have built numerous projects but did not know how to test all the components. Now I have a better understanding and know how to test most of the electronic components.

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Thank you for the answer. I found your website is very informative for electronic repair.

Keep up the Good Work!

Regards,

austin

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hi, mr jestine, how are you. i would like you help me to resolve two problems with two monitors. the first problem is like this : the raster is deformed like in figure 1( i send you a file fig 1 ), the raster vibrates horizontally a bit and it arrives a moment the form of the raster changes to best. the second problem is like this : the screen is dim, the horizontal size does not change, and when i try to change the horizontal size via the button, it does not change and the the edge of the raster become deformed. thank you.

Hi A,

The first problem could be in the power side big fat capacitor bad (assuming the curve is slowly running up). Check all secondary filter caps too with esr meter. If you get a nice voltage outputs at secondary side then proceed to next stage which is the pincushion area. You have to test out all components surrounding pincushion area. Some pincushion transistors are like d669a, b649a, d2012, d2058 and etc. Remember to check all components in this area. Some ceramic cap can breakdown when underload thus you have to directly to replace them.

As for the second problem, it could be a failed b+ section. The b+ voltage should be high (boosted) if not the horizontal would be small and can’t be adjust. Check all the components in the B+ section like b+ fet, signal to gate of the b+ fet, b+ line filter cap and don’t forget the low ohm resistor connect to source of b+ fet. Hope this helps!

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Hi Jestine,

You may remember a couple of weeks ago you kindly put me in touch with the US company who stock the High Voltage probe? well now I have my own and what an instrument!

Many thanks for your guidance on this.

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Good day to you Sir. I have a problem with my acer lcd monitor, the model is ALS1702. The problem is intermittent display.when i turn it on the display disappear in a few seconds. i already open the lcd trying to repair it but i cant find any problem. Can you give me an idea which component should i test or which component is damaged? Im happy to read your reply soon and will help me a lot on my work as a electronic technician. It will also added it my repair list. Thanks lot sir, hope to recieve your responds soon.

Hi E,
I have posted some of the lcd monitor repair tips at my blog https://www.jestineyong.com/?cat=36&paged=2

Feel free to read all of them and hope it can help to solve your lcd problem.

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Hi T,

Hi Jestine, i have a big question for you: an isolation transformers is obligatory?

Yes, it is necessary to have one to prevent electric shock. Some experience tech may not use this transformer.

at isolation transformer is connected oscilloscope or monitor to repair?

If you use isolation then you can connect the scope ground to the negative side of the primary power supplt to test out waveform from the power IC and etc. If you don’t have the ELCB will trip.

in the manual of my Fluke PM3082 100MHZ oscilloscope(yes i have buy an oscilloscope) is Warning message for use instrument only connected whit earth. If my body is isolated from earth whitout isolation transformer and accidentally i touch a 220v is a mortal danger?

It is danger when you touch on the live and the neutral line or the ground line at the same time. Neutral some people called is a s ground too!

Whit a isolation transformers what are the difference, please explain me all about a isolation ttransformer, and please sorry for this email, for disturb you whit my questions, but for me you are a electronic idol 🙂

Its okay no problem for asking me questions. Please visit this website http://en.wikipedia.org/wiki/Isolation_transformer
for more information.

p.s. after i buy your 2 ebook i have buy this equipment:

1: Solder/Desolder station whit hot hair and desolder pistol vacuum pump(ct-brand 858) + second station AYOUE 701
1: Capacimeter
1: Inductance meter
1: Esr meter
1: Flyback tester
1 Analog multimeter(same as visible in your ebook)
1: cheap digital multimeter
1: ice 680r analog multimeter
1: Smart Tweezer
1: Peak atlas analyzer
1: DC regulated Power supply whit 2 separate variable out and 1 fixed 5v (max 60V 6A)
1: Bench multimeter
1: Oscilloscope Fluke PM3082 100MHZ
1: Uni-T UT71 Intelligent Digital Multimeter (is a good choose?) link= http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&rd=1&item=220263940555&ssPageName=STRK:MEWA:IT&ih=012
1: various tools, tweezers, screew etc… + various component kit(resistor kit, capacitors, diode, transistor etc…)
1: Logic analyzer (cheap)

Wow, you are a real fast learner and i admire that! Have good day!

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Dear Mr. Yong,

Many thanks for your earlier words of encouragement.

My interpretation of your response to my DMM calibration question is:

1. Use a backup meter to check the accuracy of my main DMM after 1 year.

2. If measurements taken with primary meter appear off by large amount, run tests.

3. If tests confirm DMM needs calibration, either send to factory or calibrate via known good test signals.

However, I am happy you advised me to be aware that today’s well made multi-meters are unlikely to lose their accuracy so quickly.

Update 1:

To speed up my understanding of your book, I have been converting the eBook parts I find hard to remember into table form and concept maps.

This way I can at a glance refresh my memory of important points.

Update 2:

My aim is to begin diagnostic and repair work by the end of August 2008.

I have collected a few non functioning 12V to 110VAC Inverters and UPS systems, some of which were manufactured by the now out of business BEST Power company.

I was able to acquire a few Service manuals from the persons who used to be the local agent here in Guyana.

What I continue to learn from your eBbook is a direct influence on how fast I can begin repair of these UPS units.

Update 3:

My careful reading of your Art of Success eBook, suggested that I invest some time in learning how to quickly draw Block Diagrams for unfamiliar equipment. (i.e. complete with section explaining each block)

Today I am working on guidelines for producing these diagrams, although there is so much information out already, I will not have to re-invent the wheel for many equipment.

It seemed useful to also update & refresh my knowledge of circuit symbols (i.e. used in Schematic diagrams)

Please help me with two questions:

1. Have you started sending out your newsletter yet? I recall signing up, but perhaps I need to do something more?

I only send out my repair newsletter once a month. Have you received my August repair newsletter?

2. I read up that Circuit diagrams for electronics are drawn with the positive (+) supply at the top and the negative (-) supply at the bottom. This can be helpful in understanding the operation of the circuit because the voltage decreases as you move down the circuit diagram…. Is this true?

Yes, the voltage decreases as it past through resistors, diodes, transistors and etc. Remember that semiconductor need at least a 0.7 volt to conduct. That means if a 10 Volt passes through a diode the end result would be 9.3 Volt!

Jestine

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Hi D, For the inductor(coil), how do i recognize the coding printed on the body of the specify parts? Any reference table can you share with me?

All these are manufacturing coding and i can’t get the data too.

I not sure the whether it is over .3 or .2 milihenry or .2 above value.

You have to use inductance meter to test it out

Is this type of inductor easy to find at the Pudu (Jalan Pasar)?

Not easy as most of the inductor is quite unique in terms of the inductance value. Inductor of horizontal size and hroizontal linearity rarely have problem. I don’t think your tv problem was caused by defective inductor.

For the transistor , it is located at the secondary side join with the “Pin 1 (Vin)” voltage regulator IC (9V). After Spending time hunting for the parts datasheet, i finally have got the spec (buk9524-55) but different maker (Philips). I assume it as a Power FET and found out short circuit between (Gate, Drain, Sourch) and I can’t find this parts at Pudu (Pasar Road) .Can you confirm with me is it same parts? If yes, got any replacement for this parts?. Please guide me.

This is a special N Channel FET and since i’m at home, i don’t have the data book with me. I will go to office tomorrow to look out for this replacement part.

If the TV sets degaussing coil have got liquid leakage, should i replace a new one? Any spec for the degaussing coil?

Degaussing only have loops of coils in it unless someone accidentally poured the liquid in it. As for the spec, get back the same size of loop.

Please refer to the power point again for additional unknown parts i taken out from my PC monitor. Symptom is power on, immediately this parts sparks! and monitors directly goes off.

J6812 is belong to FAIRCHILD semiconductor and it is a Horizontal Output Transistor (HOT). If you can’t find original from pasar road, the get C5411 as replacement.

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Hi B,

Presently i have a jvc lcd tv model no. lt26ds6 that refuses to switch on. The relay ticks but it only goes to standby and the stanby light begins to flash after awhile.

Check for all e-caps for high ESR Value at the secondary side of power supply. Sometimes when the led flashes it indicates certain problem in the lcd and you need to have the service manual to get the explanation about the LED flashes.

I also have a Goodmans GTVL19W17HDF 19″ LCD HD that switches off after sometime when switched on. However at the moment it is dead without power. What do you think i should do to fix it.

In this case you have to test all of the electronic components in the power supply area which include the secondary side. Make sure there is output and if you get zero volt then concentrate on the primary side components. It could be a bad power IC, open start up resistors and shorted primary winding of smps (this will usually blow the fuse).

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6 Comments

  1. Hemesh Nair

    February 6, 2009 at 8:39 am

    How to read SMD capacitor values.

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  2. admin

    February 6, 2009 at 8:36 pm

    Hi Hemesh,

    Type on google "smd capacitor code" and you will get lots of information from there.

    Jestine

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  3. Gokhan

    November 18, 2009 at 2:41 am

    Hi, I have a GTVL19W17HDF Goodmans LCD TV the problem is comes on you can see the picture for about 1 second than it goes dark with the sound still working.

    I have all the nessecery tools but i did open it up and checked the power supply but i dont know what i am looking for?

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  4. admin

    November 18, 2009 at 7:04 am

    HI Gokhan,

    This suggest that there are problem in the inverter board or one of the backlight have problem.

    Jestine

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  5. alexi

    December 21, 2009 at 5:00 am

    HI,I HAVE READ MANY OF YUR COMMESTS AND I HAVE A PROBLEM WITH A PHILIS TV, ITS PROBLEM,WHEN YUO TERNED ON IN A FEW MINUTES IT BGET OFF. CAN YUO HELP ME?

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  6. admin

    December 21, 2009 at 11:11 am

    Hi Alexi,

    CRT or LCD TV? When it had turned off, is the power LED still light?

    Jestine

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