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Electronic Repair Questions/Answers And Testimonials- Part 52

By Jestine Yong on April 13, 2010

Hi Jestine,

I must tell you that i all your Ebooks and am surprised to find so much knowledge about electronics repairs things i would never known without your program and now am fixing all types of monitors and making good money.
many thanks.
God bless you.
Johnie J.

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Thanks Justine,,,, every time i received your letter, it was very interesting I really learn a lot and my repairing ability is increasing,,, thanks and more power to you

J.V

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Hi Jestine,

Thank you very much for the additional free information,its very interesting and useful!

I purchased your book on testing electronic components, and I´m learning a lot!

Thanks again!

Best Regards,

Victor V

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HI Mr JESTINE .Your repairing tips have helped me a lot in my repairing of electrcal appliances , keep up your good work . Thank you . I Feel Very Happy .

james h.

GRENADA

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Hello Jestine
thank you very much for your email, it is always a pleasure to receive I do look forward to it each month,it is so informative and educational in every way,I feel sometimes that you are looking over my shoulder whenever I have a problem with something .In using your commonsense approach it soon leads me to the problem,even without expensive equipment. Your knowledge of your world around you is an inspiration to us all, we have a saying in England ,” A problem shared is a problem halved”, but with you it reads, “A problem shared is a problem solved “.

Thank you once again, yours faithfully Albert.

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Hi Jestine,

Thanks! I was curious though how did you know from what i told you that by measuring the voltages at the MCU and EEPROM that it was the main board that was bad?

Thanks again for your help!

David

HI David,

This came from repair experience. By right, if the MCU got the right voltage (assuming the vga sinal cable is connected to CPU) it should output a signal to the green LED. Since now the LED is blinking and the LED signal is coming from the MCU then chances is very high the MCU or the EEPROM have problem. I do came across other brand of Monitor that have blinking problem and when the mainboard was replaced the picture came back to normal with steady green LED.

Jestine

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HI George,
I recently purchased your lcd monitor repair package.

Thanks for the support.

I have several questions. I have a power supply unit with several bulging capacitors on the secondary side. After replacing them the power supply still won’t output the low voltages. Everything is good on the primary AC side. The power supply uses the Weltrend 7515 IC contoller. I have sent you the data sheets. I believe the IC needs to be *reset* but I’m not sure how to do that.

The reset meaning if there is any excess current draw and etc the power IC will shutdown to protect itself. Reset in this case means you have to turn off and then the power On in order for the power IC to work again. However, if there is still problem in the primary or even in the secondary side the power supply will still not function even though you have reset it (turnoff/turn on power).

Also, the web site you mention in the book for looking up part numbers no longer works. Could you please tell me where I could find a substitute for this Weltrend 7515 IC? Thank you

Try check this link:

http://www.donberg-electronique.com/descript/w/wt_7515.htm

Have a good day!

Jestine

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Dear Jestine,

I have one Dell monitor was unable to view.

When power on the monitor it show white screen and nothing been shown on screen (when it connect to pc or media player)

Please advise, thanks

Paul

Hi Paul,

White screen is usually the problem of a bad LCD panel. Assuming you have check that the output voltages from the SMPS are good and stable and the connection between the mainboard and the lcd controller are intact.

Jestine
http://www.JestineYong.com

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HI Rudy,

Since, I started reading your “Troubleshooting Repair Guide” I have widen my knowledge of basic electronic prinicples in the field of servicing. I am very proud to tell you, that I can now perform general repair on some TV receivers with moderate problems.

Thanks and nice to know about that!

At present, I am repairing a Pensonic DVD player HG-932 defective regulator transistor (Q1) with shorted element. I couldn’t replace it, because there’s no markings on the body and I don’t have an schematic diagram for reference. Any assistance from your good office is highly appreciated.

Sorry i do not have that diagram. May be this short article that i have posted in my blog could shed some light about the above problem:

https://www.jestineyong.com/?p=2692

Have a good day!

Jestine

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HI Nuno,

I have bought your books, and I’m reading them with a lot of interest.
I have started by Testing Electronic Components.
In there you say that to test a lot of components you use an analogue
multimeter.
I have bought a digital one. Can’t I do all of the testings? Should I
buy an analogue?

In fact you can do the testing with digital meter but for some components like testing diodes, transistors and etc an analog meter is far more accurate then digital meter. I came across those components tested good with digital meter but fail when test with analog meter. Analog meter is very cheap nowadays. A Sunwa meter cost about USD10.00 and you should invest one.

One other question:

How can I know whe I have a simple transistor or a FET or a power
regulator? They look very similar..

By looking at the part number and search for the data spec and you will know it belongs to which component.

Jestine
http://www.JestineYong.com

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HI Beh,

please tell me if can measure the value of very low resistor in the circuit my resistor color code is brown red silver gold = 012 ohm if answer is positive

Yes you can with the help of ESR meter you can test it.

my ESR meter read 0.11 one time and one time 0.16 this resistor is ok or not ?

You have to make sure the probe is not curl or twisted otherwise you may not get the stable reading. I guess your resistor is good with the 0.11 ohm.

Jestine

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HI Felix,

hie i came across a tv with a burnt out fuse on the input side when i replaced it ,it burnt out on switching what can be the problem

It can be shorted semiconductor or even the switch mode transformer. You may need to check all the components in the power supply before you put in the fuse again.

……. secondly i have a system that has a burnt resistor and the codes are beyond recognition what can i do to get the replacement.

The best is to find the exact schematic diagram.

Jestine

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HI Joe,

I have purchased your books “testing electronic components” and “troubleshooting smps” and have found them very helpful.

Thanks for the support!

I am responsible for repairing circuit boards for a large quantity of IBM infowindow 3472 computer terminals. Many of them have shorts on them and I have fixed some using the 100w light bulb test, an esr meter, and a dvm. I have recently acquired a sencore computer monitor analyzer, a universal horizontal analyzer and an auto tracker oscilloscope. The horizontal analyzer has a built in ringer test but I’m still unsure or where to hook up the leads to test the flyback transformer. Any help you can give me would be appreciated. Also, if you know of any source where I could get the schematics, please let me know. Sam’s doesn’t have it.

If you could give me any advice on how to proceed, I would be very thankful.

Sorry i do not have the schematic. As for finding the primary winding i guess this article can give you a better understanding of flyback transformer.

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

Jestine
http://www.JestineYong.com

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Thank you Mr. Jestine Yong the problem i have problem with my monitor, I dont have picture on mi screm the power button is on and off, the monitor names is Westinghouse and model LCM-19w4; can you tell me what is the problem Mr. Yong.

HI Leonel,

It may be the power supply, inverter board or the mainboard problem. Is the output voltages from the SMPS good and stable? If the mainboard is receiving good and stable voltages and the power LED blinks then suspect a bad mainboard.

Jestine
http://www.JestineYong.com

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HI Mike,

I recently bought your course on monitor repair guide.

Thanks for the support.

I have two questions that I’d like to ask.

No problem.

First I have a HP vs 17e monitor that had a broken backlight that I replaced, that’s working fine now. Monitor works fine on auto settings, except that I can not shut it off with the power button, but it goes into sleep mode when I shut my computer off. Also when I hit the menu button, the volume displays but when I try to adjust the volume the monitor shuts down. I unplug power cord and plug it in again and monitor turns on again. Can you tell me what I need to do?

Make sure the front button is not stuck. If all the front panel button tested good then suspect a bad Mainboard. It is either cause by data corrupted in EEPROM or the MCU IC.

Second question. I noticed that you don’t talk about hp monitors is there a reason for this? Which monitors are the easiest to fix?
Actually all LCD Monitors problem are quite the same- no display,no power, display dim and etc. Once you know the principles you will know how to troubleshoot all kind of brand in the market. I can’t say which Monitor is the easiest to repair because generally all brand of LCD Monitor can have the problem that i mentioned above.

Jestine

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Mr. jestine yong, please give me advices for how to fix my monitor Samsung 713N with display on the black screen the message not optimum mode `recommanded mode: 1280 x 1024 60 HZ“ on the screen.

Thank you

Hanh

Hi Hanh,

The problem is in the mainboard MCU. This IC need to be changed or reprogram.

Jestine
http://www.JestineYong.com

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Hi,

Good Day!

I would like to ask some kind of advise if what is the best brand of cheap, reliable BGA Soldering Station in the market.

I am pretty sure you have one in your work station.

Best Regards

Viany

HI Viany,

So far my place here did not sell those cheap BGA machine. All of them are the high end type. At current moment I’m only using the normal rework station but of course it can’t be used to extract the BGA IC. Try search from youtube for BGA machine and i believe there may have some for sale.

Have a good day!

Jestine

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MR JESTINE what would cause a SMPS a humming nois .

Hi Rich,

It could be the transformer itself have problem or cause by problem in the corresponding components.

Jestine

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Hi Eloisa,

Thanks for your Web site. I read some of your articles and found it very interesting.

You are welcome!

By the way the add. luisa@lavinci.it, is not answering my request, maybe they have no parts available.

It should be info@lavinci.it

Maybe, I would like to ask you, maybe if you could help me, any other add. or idea, where I can buy the complate Mainboard, you know I don’t want to throw things which still can be repairable. The attachement is the picture of the Mainboad of my TFT Monitor BENQ Model: Q7T4.

About the history of this Monitor, the screen picture was just dark blue.

Dark blue can be the cause of bad mainboard or the lcd panel.

Maybe it was to much for them bec. I’m asking them too if they could also supply me a CPU – Processor with cooler to suit Motherboard : MS 7091, but I decided now to buy the Intel Core 2 Duo E6500 DC Box (2,96 GHz; 2 MB Cache; 775; 1066 MHz FSB).

I don’t think he sell the Cpu. He only sell electronic spare parts.

Jestine

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Hi Jestine,
its a long time since we communicated. i have a problem with a sharp television. the problem is a grey screen and some horizantal lines. could you tell me whwer to start. Are they retrace lines.
I did not get a march issue of your report.

HI Patrick,

Grey screen means no signal is reaching the CRT cathode. You may need a scope to trace backward from the RGB points in the CRT and see at where the signal had lost. It could be the color IC have problem or missing supply voltage to the color IC.

Jestine

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do you have a ebook on how to read electronic schematics????

HI Bruce,

Thanks for your email but sorry i do not have the ebook title.

You can buy one from amazon.com at http://www.amazon.com/Beginners-Reading-Schematics-Robert-Traister/dp/0830676325

Jestine

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HELLO MR YONG

actually it was the first time i was using the blue ring in repair . and i learned that blue ring just read the loops that they have
enough windding not <all loops> four types of coils that you mentioned in specifications of blue rings:
1-B+ coil
2-smps primary winding coil
3-horizontal yoke coil and may be the vertical yok coil ?
4- fly back primary winding
thnx&rgrds
beh

HI Beh,

Yes, that’s right because these four types of coils have more windings.

Jestine

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hi mr yong.

first of all thank you very much due to sending the newsletter to me.

there are some letters after main part number of some electronic components. what does these letters mean?

for example:bc107c or bc107a

can i replace bc107c with bc107a or vice versa?

thanks a lot.

HI Saaed,

Those are version. It depends on the part number, generally it can be used for all part number regardless the version. However, if you have doubt the best is to find back the original number.

Jestine

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

HI Srinivas,

Pls let me know SMD capacitor how to chek on Laptop mother board .I know useing the multi meter other than that any special tools are avalible in market.

Try visit this website:

http://www.advancedevices.com/

The mosfet Like 4800,4410, useing in laptop mother boards how to chek on board,

The best is to direct replace. However if you have the spec you may test it using http://www.peakelec.co.uk/acatalog/jz_dca55.html

Jestine

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HI Ayara,

Hello Jestine, before any question or contribution let say a big thank you for your consistency and concern in sending your news letter.Truly I have benefitted greatly from them.

You are welcome!

With regards to your April version of the news letter. There caes where faulty SMD have been detected, like diodes, transistors, resistors etc, and their SMD replacement not available, will it be out of place or ‘unprofessional’, to use descrete components for replacement where possible. Though I have tried it severally before and the equipments work very well. Whats your view.

If it works then yes you can use it. There is nothing about “unprofessional” because this is the only way one can solve the problem since it is quite hard to get the SMD parts.

Have a good day!

Jestine

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

HI Alex,

I come across a FET J370, May I know where I can get it’s data sheet or information.

http://www.alldatasheet.com/datasheet-pdf/pdf/108807/SHINDENGEN/2SJ370.html

Actually, I am also looking for replacement part, do you know where I can buy J370.

According to my databook the replacement number is 2SJ236,2SJ293, 2SJ321 and 2SJ390. You may have to check this from your local electronic store.

Have a good day!

Jestine

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HI Noel,

Thanks for this step by step explanation about repairing mainboard its a very nice explanation cause I’m one on that field.Its true its very hard to repair a mainboard with out proper tools and test equipment.Especially the parts cause some of the manufacturer use some special parts that you can’t find in the market.

You are right!

Only manufacturer have that used for repair,you need to send your card to them for repair.In my experience in this field I almost reach to open some Hybrid IC to repair it replace some SMD inside the HYbrid IC,cause I can’t find the whole IC,even the part number does not exist in the net.

I came across this problem too.

And one thing they use PLD on the card,like last week I have a card for repair,the trouble is the PLD IC,its a GAL16V8B has a corrupted program.The good thing is my client have the same machine model so I can copy the program from the other card,but I was surprised the PLD program have locked and I can’t break the code.So the customer don’t have a choice they send the board to manufacturer.

Some IC can’t be copied out. Thanks for sharing!

Jestine

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HI Bailing,

Yesterday a customer sent me this local product CRT monitor. The problem is while contrast at its lowest minimum, the monitor still have a quite bright raster, causing all the colors to be chaotic.

I took voltage measurement at the CRT pin, found the G is 58V, while R&B is about 50V. G1 is -48V, G2 is 440V. Also I found that the Posistor is quite hot, causing its outer case color to be somewhat grey, not clear black anymore, is this normal?

Posistor will usually run hot but if there is color patches and the monitor can’t be degaussed then there is problem with the posistor. G2 voltage seems to be very high and you may need to lower it down. In some monitors, the RGB voltage may have some variation and not necessary have to be all the same.

This CRT board is using LM1282N Video Amplifier System. I have checked there are no bad capacitor on the CRT board, G1 resistor is also OK. Do you think I have to replace this IC?

If after the adjustment of the G2 did not help you may need to replace this IC.

Jestine

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Hi Sir Jestine,

Thank you very much for the monthly newsletter. By the way, I sent you picture and I would like to ask a question about it.

My questions are:

1. Base on the picture, the black with round shape, Is it considered an IC?

2. Is it prone to damage? If it is, Is it repairable?

I ask this because I had a digital meter which is not functioning anymore and I checked all the components and seems to be okay.

Thanks and more power.

I will be waiting for your reply soon

randy

HI Randy,

Yes it is an IC and it can’t be repaired.

Jestine

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I have an Acer AL1716 lcd monitor. It starts up faintly red but quickly seems normal. At random times, the whole screen will begin flickering and will continue for about 3-5 minutes then suddenly stop as if nothing was wrong.

I suspect the monitor because when I disconnect the video cable to the monitor, it continues to flicker. My question: do you think this is a ccfl tube or the inverter?

Hi billy,

It can be both but before that you may have to make sure that the filter capacitors are okay and the output voltages from the SMPS are good and stable.

Jestine
http://www.JestineYong.com

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HI Toby,

Thanks again for another educational article. I appreciate the time you take in writing and illustrating them so we can get a clear picture of what you speak of.

Yo are welccome!

I did a search on BGA I.C. stations and found them to be quite innovative but expensive. I saw one model made by Zephertronics costing over five thousand dollars. I didnt realize they would be that costly. I guess if and when I grow and expand I’ll invest in one but for now I’ll work with what I have.

Yes those BGA rework station is very expensive.

I’ve been trying for about two years to find a circuit board for an LCD t.v. Its an RCA L32WD22. The circuit board has a number: 715T2300-F.

When the t.v. is powered on the LED on the front turns green for a few seconds, then blinks orange four times, then goes off. When the power button is pressed again, the light stays on solid orange. When I unplug the cable from the above-mentioned board and press the power button, the green light stays on until I switch it off.

Could you assist me in locating this board. I have been able to find only the power supply board online .

Sorry i have no info on this. Have you try shopjimmy.com? You may also try email Luca at info@lavinci.it to see if he has one or not. By the way, LUCA is from Italy and he sell LCD TV and Monitor parts.

Have a good day!

Jestine

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HI Liviu,

Thank you for the ESR tester.

You are welcome.

After I had to fix the first dot (LED was A with K swapped) I could use it. I just want to ask your opinion over the values read measuring the capacitors on the main board:

Tantal: 4.7u/16V ESR: 1.1

4.7 0.68

4.7 0.77

4.7 0.86

4.7 1.0

4.7 0.63

4.7 0.91

4.7 0.79

10u/16V 1.1

10 0.22

22u/16V 0.54

22 0.56

1u/25V 0.25

1 2.6

1 2.9

1 3.6

1 1.7

1u/35V 0.28

Aluminium 100u/25V 0.16

100 0.15

Please let me know what do you think about the values measured. I still have not measured the SMD capacitors (which are over 1 uF) as I couldn-t identify them. The main problem was that the LCD display was freezing the image and now I’m looking for bad caps.

I couldn’t understand why in your table for ESD values you put 1uF/16v max value is 5. Shouldn’t be much smaller?

Actually i did not put that value. It was from the ESR meter designer Mr Bob Parker. The chart is just for reference purposes/guidance.

About the value that you have checked on the mainboard, since you checked it it on board, there may be some connected parallel thus lowering the ESR value. I suggest that you take out one of the cap and check the original ESR value and then compare the value of the cap that you want to check on board. Any big differences in the value may indicate problem in the cap but then again to double confirm it, remove the suspected cap and recheck it again.

Jestine

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7 Comments

Arnold Codilla

April 22, 2010 at 10:20 pm

Hi Sir Jestine:
how are you? hope your ok by the way sir thanks for the news later about in electronics idea. good luck thanks and more power your GOD BLESS.

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admin

April 23, 2010 at 8:31 am

Hi Arnold,

You are welcome!

Jestine

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Charles Burnette

February 24, 2015 at 6:58 am

I am having a problem with a Dynex DX LCD32 tv model no. E327AZNK2WBYNN.
The tv has been turning on and off on it's own. Have done the hard reset by unplugging the cord overnight and plugging it back in with no results.
I took the back cover off to inspect the boards and didn't see anything out of the ordinary such as bulging and leaky capacitors. I am stumped.
The main board is a 715t2300-3 and the power supply board is a 715t2463-3. My first assumption was the power supply board but it comes on fine but then it turns off and starts cycling on and off on it's own. If I leave it plugged into the wall receptacle it will turn on and off on it's own until I remove it from the power source.
Any help will be appreciated.

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- Jestine Yong
  
  February 26, 2015 at 10:14 pm
  
  HI Charles,
  
  It can be due to the power supply board itself or the mainboard. This means if the mainboard MCU IC sending a on/off signal to the power supply then the power supply will be turning off and on. I suggest that you check if the MCU ic is getting the right dc supply or not. If it is good and stable then you may need to check if the On signal to the Optoisolator ic is stable and not turning On and off.
  
  Jestine
  
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- Robert Calk
  
  February 27, 2015 at 8:49 pm
  
  Hi Charles,
  
  I am wondering if the on/off switch is bad. Did you check it?
  
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Jason Bowen

January 29, 2016 at 2:38 am

Hello Mr. Justine! I have a Westinghouse LCM 19w4 monitor that flashes white then the backlight goes back off when I try to turn it on. The power light remains on so I'm pretty sure the main board is OK, but I'm not sure whether my power supply or the backlights are bad. I think the display board may have an issue too for it to blink white instead of displaying something. How do I go about solving this?

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- Jestine Yong
  
  January 29, 2016 at 10:59 am
  
  Hi Jsaon,
  
  If the output voltages from the power supply are good then suspect one of the backlights have problem. Make sure all the cables are properly seated. If the power LED light is green/white the mmainboard is probably good but if the color is Red then the mainboard can be the problem.
  
  Jestine
  
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