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Electronic Repair Questions/Answers and Testimonials- Part 23

By Jestine Yong on November 23, 2008

Hello,

I just wanted to thank you for your quality e-book. I ordered the LCD Repair book since we are now in business repairing laptops and LCD monitors. You have done an excellent job

Thank you very much

L.B

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Hello Jestine,
I read your e-book, testing electronic components and I really love it.
It’s amazing how simple is to be testing the components.

O.V.C

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Jestine

Dear Mr. Yong, can i ask question.. i have jvc tv 21″ it is blurry whwn first open then after 2hours it will slowly became clear…my suspect is defective tube but i bought this tv 6 years ago..hope you can help me…im planning to buy an e-book if i have enough money ..thanks a lot.

Hi Jose,

It could be the defective in the flyback divider in flyback transformer. Replace the flyback should cure the fault.

Jestine

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Hi D,

Here are your questions and answers:

I have a Dell that won’t turn on the lamps but it mounts so that all the components are facing down. What’s the best way to power up the power supply / inverter board out of the case so I can get to the components to test them?

This is actually a headache for technician. As for me i will first look at the symptom and troubleshoot on that area and fix everything and retest again. In some cases for voltage testing, i actually solder couple of wires to certain test points to see the result and from there i could roughly estimate where is the problem.

Does the board need the metal chassis for ground or can you power it up without it being screwed to the chassis (metal case)?

It does not need the metal chasis and you could clip an alligator clip between the ground to the board under test.

Is there some kind of test bed you can buy to put boards in to test them safely out of their cases?

I place the board on a square sponge while some tech place the board on a big piece of thick rubber found from hardware shop.

Best regards,

Jestine

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Dear Mr Jestine,

How about fan and fluorescent lamp capacitor’s. It is polarized or non polarized type.

Regards

Hi H,
It is a non polarized capacitor.

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Hi A.B,

Here are your questions and answers:
hi how r u.

I’m fine thank you.

you did not tell me about samsung lcd when i attach with cpu only it display “out of range message” and only show the two frequencies i did every thing and changed every frequency and change many cpus but same problem 4 lcd with this fault are in my workshop and i bought your e.book for these complication problems but could not find any solution concern above mentioned fault pls help me but many other very useful tips i found in that book regarding inverter feedback in this way if a lamp is damag i can use with other lamp if i tape the feedback connection thanks.

As mentioned in the previous email, the problem with the samsung LCD is the bad MCU which there is no part and you need to replace the whole board. It was the software inside the MCU had corrupted that cause the out of range problem. It was a common fault.

If you have other questions please do email me again.

Best regards,
Jestine Yong
http://www.JestineYong.com

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dear sir.

i am having problem with my crt monitor 17″ normal.i cannot adjust the horizontal side of it.i cannot make a little bit small to fit my window xp. i hope you can help me

thanks.

danny

Hi Danny,
Check the pincushion transistor for shorted reading located nearby flyback that mounted on a heatsink. Sometimes a shorted modulation diode near HOT could cause similar problem too.

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Hi Ken,

Here are your questions and answers:

I don’t know if you recieved my e-mail earlier,

I guess i did not.

but I’m trying to find out if a set has a high voltage problem, will the set ‘s high voltage come up and shut down very fast?

Yes, the best is to use the high voltage and test it out.

If so, should change the voltage regulator?

Check for excessive in the b+ voltage to the flyback

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Hi Jestine,

I think you are long enough to repair computer problem, and I think you must also come into this kind of problem. I have some writers that after using for sometime are very selective in reading a disc, and those are not because the disc is bad or has some scratch on them, because I’ve confirmed them on my other working CD/DVD writers, they can be normally read.

Could this kind of a problem get a solution, or we must just buy new one,it’s a pity to discard them because for some CD/DVD they are still OK.

Hi B,

Yes, i do come across with this problem before. First get the lens clear from any dust. You can clean it with any recommended DVD solution. If the problem still the same then it is the lens problem and you need to replace the whole lens assembly.

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Hai JY,

I already purchase your e-book(testing electronic components +++ 6 bonus). I make a conclusion that your e-book quite helpful dan easy to understand.

Tq.

Warm regards,

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Hi Mr JESTINE
What causes a thin vertical line to appair on a 17” lcd-tft monitor even powered and not connected to a PC?
Thanks a lot for responding.

Hi S,
A bad LCD panel and quite common in lcd monitor and is beyond repairable if it is permanent.

===========================

I HAVE TCL TV BY PHILIPS. IT HAS A SHORTED DIODE HER108 ULTRA FAST SWITCHING DIODE 1000 V. 1 A 70 NS IT IS GOING TO FET K2996. I CANNOT FIND ONE. CAN IT BE SUBSTITUTED BY 1N4007. I RESEARCH IN INTERNET I SEE ECG 575. UF1000.UF108. 106. UF1010. BUT NONE OF THIS CAN BE BUY HERE IN OUR PLACE. CAN RU2B 1000V 2.5A 250NS CAN BE A REPLACEMENT TOO. THANK YOU SIR. ABOUT THE TAPE DECK I CANT SEE THE PROBLEM IN MECHANICAL. THANKS FOR THE HELP.GOD BLESS U MORE.

You have to get original or try BA159. 1N4007 will go shorted immediately due to the slow speed.

Hope this helps!

Jestine

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The unit powers on just as normal. When you press the power button, the monitor works for about two seconds and then the screen goes very dim (the bulbs go out). I removed one bulb and then hooked it up outside of the monitor. I powered the unit on and the bulb shined bright for two seconds and then went out. So…the bulb works but only for a couple of seconds. You can see the screen on the monitor but it is very dim and dark.

I tested components and put the monitor back together. For some reason, it works now. The only problem now is light vertical streaks across the monitor when it is turned on. The display is also dimmer than normal even at 100% setting. Weird.

Hi R,

From your description it seems that the problem could be in the bulb as an intermittent bulb could cause intermittent shutdown problem. check also for any loose connection cable of the backlight connector and dry joints in the high voltage transformer.

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hi jestine
got an hp zv 5000 thats sutting down can u help?

Hi A,
Shutting down of the display but the system is running could indicate fault in the inverter or the backlight circuit of your notebook. You can open up the casing and see if the backlight has turn red or not or have dark angle at both side? If yes then replace the backlight. Hope this helps!

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Thank you.Very soon I will have more Questions about lcd,s.Right now I have a lcd monitor. the name is insignia .There is no power, the power led keeps blinking.I mean shut down .the power supplies has the the 5v,24
volts .Iknow the is a short no fuses into the main board .I do not have the shematic.the inverter has two fuses 4amps they are okay.What do you think.

Hi J,

If the output is good and steady (5 volt and 24 volt) and the power LED blinks then most probably the problem is in the Mainboard. This problem has happened many time in the Samsung LCD Monitor and the actual cause was the bad MCU.

Jestine

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I put an inline 250 volt, 3 amp auto fuse in a plastic fuse holder to replace a bad SMD fuse on a few inverter boards. It works fine but is it ok to use a 3 amp fuse or should it be a 2 or 2.5 amp fuse? I don’t want to risk one catching on fire….Is a 3 amp 250 volt inline fuse ok to use on the inverter board?

Thanks!!

Hi D,

The best is use back the same rating of fuse and the auto fuse element looks thicker than normal fuse. It is not recommended, You can get a fast blow fuse and think of a way on how to solder the big fuse into the smaller pico fuse location. With this way you can sleep well!

Best Regards,
Jestine Yong
http://www.JestineYong.com

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Hi Jestine Yong,

I have some trouble in fixing LCD(HP w1907) at the moment.
It has a burnt fuse.
So, I replaced it with the same type fuse.
But it blows as soon as I plug in. 3 times I tried it and same result.

Could you advise me how I can fix it and the reason?
Without fuse replaced, there is no power on.

It would be a waste to throw it away.

I’m looking forward to your reply.

Thank you,
T.Y

Hi T.Y,
Fuse blown indicate something serious in the power supply. Try check on the bridge rectifier and the power FET (If it has one). If it doesn’t have power FET then the cause should be in the Power IC. Hope this helps!

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Hi Jestine!

I am working on an allen bradley monitor which has a problem with contrast. I can’t adjust the contrast from the trigger. At power up, it comes up bright then it goes dimmer and dimmer. Do you have an idea to share. By the way, I appreciated for the november news letter, it was so helpful.

Thanks!

Hi E,

It could be a weak lamp. Check that the output from the two high voltage transformer are good.

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Hi Derick,

Here are your questions and answers:

I want to buy digital multitester, how will i know if the test voltage output of the tester is less than 0.6 volts?

You can test the probes using another digital voltmeter.

I have also a problem with my monitor, the output color is red. I don’t have any experience in monitor repair but I’m really willing to learn.

Do you have a color test pattern if not you can download free from the internet Just type in the keyword and you will get some result. With the color test pattern you will know which color is missing. Okay back to your case, check for dry joints at the crt board and compare the resistance of the three color transistor (if have) because some design have the three color transistor built into an IC like part number LM2469T.

Compare the three transistor voltage too. Please keep me update on your progress. Here is a link to the Monitor repair site by sam goldwasser at http://www.repairfaq.org/sam/monfaq.htm

Have a good day!

Best regards,
Jestine Yong
http://www.JestineYong.com

================================

Hi S,

Here are your questions and answers:

Thanks for your reply.

No Problem!

Since I do not have another set of backlight and inverter, I did followed your first advise and it worked. I did been able to execute a continuity test on the inverter and the test succeeded, while the same continuity test on the backlight bulb failed.
Also, I did observed a little black ring at each ends of the backlight and, correct me if I’m wrong but, I think this is a sign of burned bulb. Now, I think that I can diagnose that this backlight IS burned.
So, I will order a new one.
Thanks again for your time and help.

Yes for sure the backlight have problem!

================================

Hi D,

Thanks for the photo. Okay a quick guide. Tube usually consist of 4 wires (2 wires for horizontal and 2 wires for vertical). For your information dick smith flyback tester is not design to test on vertical coils. It can only be use to check on horizontal coil. How do we know which one is horizontal and vertical coils. From the first photo that you sent me, no 3 and 4 is horizontal coil because it separated further than no 1 and 2. The no 1 and 2 is vertical coil. Horizontal coil have very low ohm and vertical coil have about from 3 to 10 over ohm. Hope this helps!

Jestine

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Hi D

Here are your questions and answers:

These are the fuses I’m using to replace the SMD fuses on the inverter board… 125v, 3 amp, fast pico fuse. Are these ok in that circuit?

Yes is is ok

The fuse I used on one inverter board was a glass / tube 250 volt, 3 amp, not the flat plastic automobile fuse. That one ok or should I replace it with a pico ?

Glass type fuse is okay as i use that one too.

http://www.bluestar-online.com/3_AMP_PICO_p/10-070.htm

Are these good to use to replace the SMD fuses in the inverter board? Cant read anything on them usually.

Yes you can-no problem!

I cant find the volts and amps rating on the small smd fuses on the inverter boards. You said a while back to use a 2.5 or 3 amp fuse it its place? That correct?

Yes it is correct

If you have other question please do email me again.

Best regards,
Jestine

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Hi R,

Here are your questions and answers:

I have a question please. I used the manual to troubleshoot the power
board on this Samsung Suncmaster 940BW. I replaced a few components
and now have power. My problem now is this split screen. One side is
normal and the other side is all white with a few color lines up and
down. I assume this is the LCD screen itself and was wondering if you
had any ideas on what component on the LCD screen would cause this?
The connections to the glass look very good and sound. I am stumped.

Okay got your picture and i have came across many with this kind of problem and Yes it is the LCD panel fault. Most probably failure in the LCD controller IC in the lcd controller board. that no signal was sent out to the lcd driver ic thus you could only see white display at one side. A repelacement of LCD panel is the best solution. Hope this helps!

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Hi H,

Here are your questions and answers:

I have problem with my Dell E173FP, with frequently appear contrast/brightness set-up console menu

And the cursor is running up and down,

Even though I never touch the soft button switch. Then it will disappear by itself.(for more detail see attachment file)

Could you give me advice on this problem??

There is only two things i could possibly cause this kind of problem. First is the front panel button-Check all the button with ohm meter and make sure there are good. Second-it could be a file corrupt in the eeprom ic and it need reprogramming.

Hope this helps!

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Hi R,

Here are your questions and answers:

Thank you for the advice. It was fun to follow your advice on component testing (for the power board) but then only to find the LCD screen was bad.

Sometimes even at my side here i also have to face this kind of reality. I always treat lcd panel just like picture tube. When a crt monitor picture tube already bad, the best is to replace it with another tube.

Since I am doing this to learn, I would like to try and fix the LCD screen instead of replacing it. I realize this may be more work than it’s worth but I want to use this unit to learn from. Maybe I will find that I can’t buy the IC and the only option is to buy a new screen. Anyway, thanks for the advice. I have been learning a lot by reading your ebook.

Yes you may do your own R and D on this area-wish you success and glad that you liked my ebook.

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Hi D,

Here are your questions and answers:

First of all, i want to thank you for all your help you have provided me through your books and downloads.

You are welcome!

I do have a few questions for you if you could be so kind as to help me with your advice. I recently made a decision to pursue my life long dream to become some sort of Electronics technician. I have always had a huge interest in anything electronic and to figure out how it worked. I also had a huge interest in automotive mechanics and that seemed to take up the first part of my life. Now i want to get out of that and try to put together some sort of electronics repair shop. I started gathering as much data as i could find to further teach myself as much as possible. I am also trying to set up shop and putting together a starter workbench. My question to you is this: With all the knowledge you have in the industry, what test equipment would you recommend for a person starting out and building his workbench up on a STRICT budget. I already have a few things that consist of a Fluke 179 meter, and a hakko soldering station, a vom and a small power supply. I sure your very busy with your classes and all (that i wish i could be apart of in the worst way!) but any advise here would be greatly appreciated.

It depends on what repair field you are in. If you are in the Monitor/TV repair field i guess you need a flyback tester, digital capacitance meter and scope is a must for easy troubleshooting. Get also an ESR meter and you would love it. Without ESR meter it woule be a little tough to do bad e-caps in electronic board.

If you have other questions please do email me again.

Best regards,
Jestine yong

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Hi J,

Here are your questions and answers:

This unit has no back lite no power lite, no high voltage. Unit does
test good for 12 volt and 5 volt to the control board. On the controller
board I have a Aic 1084-3.3pm
I believe is a voltage regulator. I have 5 volts going in and 3 volts
coming out. I checked all “0” smc jumpers and all smc fuses. Also
checked all capacitors for esr. Checked for open resistors and as always
cold solder joints. Stuck on this one and cant get anything out of it.
If better pictures would help please let me know. Any suggestions
woulld be greatley appreciated. ..Thanks!.

This acer model have a common fault of faulty MCU and it cause no power symptom where may technicians thought it was the power supply fault. Only by replacement of a new board that solve the problem because there is no supplier selling this kind of ic.

==================================

Hi J,

Here are your questions and answers:

This monitor works great for about 5 seconds then shuts down the power
light stays green. If you turn the monitor off and back on it will do
the same thing over and over.. I replaced all electrolytic on the
inverter board as they were all puffed up and had bad esr. I also had to
change 1 capacitor on the control board for bad esr. The inverter board
is burtn where 4 smc’s are located on the bottom these are u101, u102,
u105, u105 labeled looks like: 4606 BDSd6y. I also checked this
board with working screen and back lites. Any suggestions would be
greatly appreciated.. Testing tools that I have are Variable ad/dc
power supply, Transistor testers, Multi meters (several), 60 mhz
Tectronics oscilloscope, Esr meter, Audio signal tracer and signal
generator, and I just bought a dick smith flyback tester but its not
here yet. Thank you !

If you have confirm is not the back light problem then you can perform the resistance test on the four of 4606 IC. it should roughly have the same resistance. If you found one of them have different resistance then concentrate on that area. Next find out the datasheet of the inverter ic. once you got it then look for the output pin. When display goes off the supply still have to be there otherwise suspect a bad start circuit or even a bad mainbaord that stop sending the On signal.

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Yes sir,thank u,that is my firts reparation on lcd monitor,i did crt monitor before.All your information helps me so much.After check,i found a transistor faulty (FU9024N).But it is hard to find this part in CANADA.I have to order it from USA.Thanks,see u next time.

T.S

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Thanks Yong,

I got it all downloaded and printed.

Looks pretty good.

You might want to write another book; repairing motherboards (incl. Laptops) with flowcharts.

Unfortunately the mobo manufacturers do not give signal diagrams away.

I have just started using an oscilloscope; but I still have to learn a lot.

Anyway, very good book.

Regards

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dear sir,

I have a 17″ crt monitor which dont have power.

but when i short the capacitor of 450wv 220 micro farad it blows like gun fire.can you help with this

thanks

Hi D

It seems that either there is a resistor open circuit or the power IC have problem because the voltage at the cap still remain even though you have off the machine.

Jestine

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Could you kindly sort on a power supply of panasonic tv using str 6307.The problem is that output is too low b+ 27 no 12 and 24 volts to the other component but the stand by led is glowing very good. I have changed all the semiconductor but still the power is low.Please help cause i have also changed flyback.

Hi A,
Sometimes a bad components like e-cap and low ohm resistor changes resistance could cause output to be low.

Jestine

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8 Comments

ashish jain

March 12, 2009 at 8:38 pm

Dear Mr Justine,
I have a started a workshop to repair Jasic inverter welding mc from Shenzen china.
As my staff is new to electronics.Do you have special book for troubleshooting the problems in inverter welding machine? or any book for guiding the user how to test diff electronic components especially IC,votageregulaor IC,optocoupler,mosfet aand inductors.Please reply asap

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ashish jain

March 12, 2009 at 8:43 pm

Dear sir,
How to check a 6 or 8 leg IC for output?
Keep one probe on one out pin and other on.......(which is common or 0 V pin)

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admin

March 13, 2009 at 7:59 am

Hi Ashish,

You need the data sheet of the ic and you can find it from the internet, .Look for the ground pin.

Jestine

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admin

March 13, 2009 at 8:01 am

Hi Ashish,

Yes the best book for your staff is the http://www.TestingElectronicComponents.com

Jestine

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Kedmy Aroche

February 20, 2010 at 2:24 pm

Dear mr. Justine
i have a crt motitor with lm2469t chip broken, but i don find any replacement, the NTE online cross reference dont find any equivalent, you can help me.

thanks

pd/ sorry but my bad english

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admin

February 20, 2010 at 11:48 pm

Hi Kedmy,

Try lm2468t instead.

Jestine

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jojogreg

September 2, 2012 at 9:05 am

Hi jestine,
I have a problem troubleshooting AOC monitor 16" wide screen when plugging-in the power cord to the power outline the LED power indicator light already without pressing the power button and this monitor has power but no display..I did measure voltage at the pico fuse connected to supply inverter board found 12volts but no voltage measure at the input TL494I Inverter IC..can you pls.advise what i do next..
thanks,
jojogreg

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- Jestine Yong
  
  September 3, 2012 at 8:16 pm
  
  Hi Jojo,
  
  It could be either the eeprom or the MCU data have corrupted because no signal was send to trigger the start circuit thus there was no 12 volt supply to the inverter ic.
  
  Jestine
  
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