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Electronic Repair Questions/Answers and Testimonials- Part 56

By on June 7, 2010


Jestine,

Nothing nice to say but thank you so much for this nice project. as of now you’re still the top one i ever found in all website. God will bless you more.

Jerry

 

HI Noorishkandar,

1) Berapakah nilai voltage dari SMPS ke Vertical IC vcc pin ?

Dalam lingkungan 12 hingga 20 vdc.

2) Apa akan berlaku sekiranya nilai voltage heater di crt board kurang dari 6.3 vdc ?

Gambar gelap

3) Berapakah nilai voltage dari SMPS ke input pin horizontal/vertical oscillator IC ?

Biasanya antara 9 hingga 12 vdc

4) Saya sedang membaiki sebuah monitor brand QDK..masalahnya no display dan saya telah gantikan ceramic capasitor yang dekat line G2 di crt board.Bila saya switch on power monitor kembali berfungsi dan display pun ok tetapi bila saya cuba run computer game dia terus shut down dan keluar blackspot di tengah-tengah screen monitor.Pada pandangan anda apakah yang menyebabkan perkara ini berlaku?

Ertinya ia dah shutdown. Kamu kena check B+ voltage dan pastikan ia mencukupi.

jestine

 

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

 

hi jestine! i have samsung fax machine given by our tenant, the problem is when i power it on, the display on the lcd panel is only the date and time even when you press the menu boton, nothing changce. is the microcontroller problem? please give me a hint about this…thanks and god bless to you and your family…

 

HI Rommel,

Sorry no info on that because i do not repair fax machine. Usually this kind of problem is related to IC. It could be the microcontroller or the eeprom ic.

Jestine

 

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

 

Hi Eric,

Hi Jestine, how doing ? hpoe everything is ok with you and your family.

I’m fine thank you.

Here i am bothering you again for your expert advise.
My optiquest Q71 has been going for quite sometime now but has developed a problem. Ocassionally the screen gives a little flicker and the picture gets smaller for a brief second and then back to its normal size. it is as if i am trying to adjust the pinch cushion. It works fine otherwise. what could be the likely cause of this problem?

try check the internal capacitor of the monitor

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

Have a good day!

Jestine

 

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

 

HI Bailing,

To my surprise the hissing noise ( like tire air leakage ) come back again the next day. It seems the noise will usually come especially when the monitor being cold started. Anyway I had returned this set, saying to the owner that it is picture tube problem.

Then that was very loud. I have not come across such problem in picture tube.

Have you ever found flyback anode cup problem ( f.e. the contact point is not good, etc ) when repairing CRT monitors?

If no one tamper it before then usually all the anode cap contact point should be intact.
No i have not come across contact point problem in anode cap.

The Treq monitor G1 circuit is OK, and I just put it back and try powering it on again. This time after I changed the color temperature, the strong white raster disappeared ( back to normal ). I took voltage measurement to recheck and got G1 -73.4V, G2 541V. How to lower the G2 voltage since the flyback doesn’t have the screen pot? Since the display is already normal, do I still have to lower the G2 voltage?

If the display is normal then leave it as it is. If you want to lower the g2 voltage down you can try to test around with few resistors value. Try connect a 1 meg resistor from the g2 line to cold ground. If no changes then lower it down to 470 k then to 220k, then to 100 k and etc till you get the normal raster that you want.

How to read this color resistor, please see the attached photo.

If ignore the black colour band then you should have a 6.8 ohm resistor.

 

Jestine

 

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

 

 

Hello Jestine

 

I would like to ask you about how we can know the value of a smd chip capacitor if no values are printed on it. Does the value depend on its physical package size ? I don’t have a meter that can got to  pico farad range, so i can’t measure the value.

 

Kind Regards

 

Ravendra (Fiji)

 

HI Ravendra,

It is depends on the manufacturers. Since this type of cap do not have standardize code, it would be very dificult for us to locate the value especially if we do not have the digital capacitance meter. Usually when you found one of these caps you will surely could locate the same cap at the surrounding area. Then use a digital capacitance meter to check the value.

Jestine

 

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

 

HI Noorishkandar,

Hai Justine..saya sedang membaiki sebuah TV 21 inci jenama Sanyo.Masalahnya tiada power tapi bila saya tukarkan Color TV Horizontal Deflection Output Applications dia boleh switch on cuma gambar dia macam terganggu seperti ditarik-tarik..Bila saya on kan lama sikit dia terus tak boleh on lagi.Bila saya chek di output SMPS Transformer tiada output voltage seperti 12V, 20V,130V dan sebagainya.Pada pandanngan anda dibahagian manakah harus saya periksa lagi?Saya harap saudara dapat membantu.

Sekiranya ia tiada output ada kemungkinan komponen shorted kat secondary ataupun masalah di power primary side. Kamu kena pastikan bahawa HOT adalah ok sebelum anda check bahagian primary.

jestine

 

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

 

Hi jestine

I bought your Lcd Repair guide a day ago and i have managed already to repair 2 screens using your techniques.

Regards
Val P

 

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

 

 

HI Noorishkandar,

1.Saudara Jestine,saya nak minta awak terangkan bagaimanakah nak check B+ voltage?

Check dgn multimeter.

Dekat point mana harus saya letakkan probe merah digital multimeter dan berapakah bacaan digital multimeter tersebut?

Voltage bergantung kepada model. Sila masuk laman web ini:

http://www.scribd.com/doc/2957819/TT204-Identifying-television-SMPS-problems

2.Bagaimana saya nak check voltage pada setiap pin secondary transformer bagi sebuah monitor 17 inci?Boleh ke saya check voltage supply pada bahagian primary transformer dan bagaimanakah caranya kalau saya menggunakan digital multimeter?

Anda tidak boleh check pin transformer kat primary dan secondary kerana ia adalah ac yg mempunyai frequency yg tinggi.

3.D2634 yang bentuknya seperti HOT yang berada dekat dengan FBT tu sejenis Transistor ke?

D ertinya 2SD2634 dan ia adalah transistor

4.Bagaimana  hendak check regulator ic menggunakan digital multimeter dan apakah yang berlaku pada moniotr jika regulator ic ni rosak?

Bergantung kepada IC regulator terletak di bahagian mana. Sekiranya ia berada di kawasan color, maka tiada output supply ke color ic dan Monitor/tv tiada gambar. Kamu kena tahu apakah spec untuk regulator ic tersebut. Selepas itu anda kena test output regulator IC dgn probe warna merah.

Sekiranya anda hendak jadi pakar dalam testing electronic components dan electronic repair dalam masa yg singkat saya cadangkan anda dapatkan ebuku ini Testing Electronic Components

Jestine

 

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

 

HI Mike,

HP 24-inch HDMI monitor
Model# w2408h
I have the power supply board out of it and I am testing it, when I plug the power to it and test the voltage at the filter cap the voltage fluctuates up and down.
the symtoms are (No Power)  I have replaced all caps eccept the filter cap, I also replaced some resistors and a fast recovery diode.
Do you have any suggestions on what I should do next, and could you tell me if the voltage should fluctuate.
the filter cap is rated 150uf/450v,105degrees, not sure what the esr rating is for it but my meter reads(.56).
I have bought some of your books and plan on buying more. I just need a little help if you can.

It should not fluctuate and it should have a steady 300 to 330 VDC. Try change the filter cap and retest. By the way, thanks for the support on my ebooks.

Have a good day!

Jestine

 

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

 

HI Max,

I have been keeping my track on your latest information in regard to repair work.  Do you have any information to determine the faulty diodes including zener and TVS diode in the circuit?  I do not want to remove and test the normal, zener or TVS diode out of circuit.

No at the moment. It is still more accurate to test it out of circuit.

 

What about finding faulty (NPN) and (PNP) transistors and resistors in the circuit?

For transistor, you can solder out the collector and emitter leg but for resistor i still prefer remove one leg out for accuracy purposes.

 

Furthermore do you have facebook?  So that I can buld my networking with you and other people.

 

Sorry i do not have facebook. Just email me when you have electronic repair question.

Have a good day!

Jestine

 

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

 

HI Gopal,

I have two Samsung 45Bn monitor, both have EHT and B+ FET changed due to their defect. But now the problem is that both having display 1/2 ” less width from both sides and it is adjustable but not to full screen. I have checked all the related components but could not solved. Supply voltage is 56v (normal) and B+ voltage 105v. I think it may be due to the new EHT. What is your opinion.

If the eht is not original then it could cause such problem. You may need to check the modulation diode and related circuit.

Can i increase the width any way by changing capacitor value or something else.

It is not recommended as this would defeat the safety of the Monitor especially the level of the x-ray it produced.

I have read lot of articles from your website. Most of them were written as FET. Now i am very confused about FET and MOSFET. Kindly explain how to identify FET and MOSFET using digital /analog multimeter. What are the characteristics difference between them. In which type of circuit FET and MOSFET are used. Can i use FAT in place of MOSFET or MOSFET in place of FAT.

FET is actually Mosfet. It is easy to call FET then Mosfet. As for the article of testing FET, i have compiled it into my ebook at Testing Electronic Components.

Jestine

 

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

 

 

hi i got your ebook so i can fix my lcd it is a 1909wb it come on and then the backlight go out so i tested the LD1117AV33 it is a voltage regulator and win i put 5.9v in to it it ouly puts out 0.39v is this a bad one you can see the datasheet at

 

http://www.chipcatalog.com/ST/LD1117AV33.htm

 

piz help thank you

 

HI Raymond,

Yes the voltage regulator ic have problem. But before that you may need to check if the output line have any shorted components or not because a shorted component can cause the 3.3 volt to drop. If you have tested this ic off board then surely this ic have problem.

Have a good day!

Jestine
http://www.JestineYong.com

 

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

 

Yes thanks I have downloaded the free report . I have a question on a tv
Tobishi 5101. It had a power surge,but now I have replaced a couple off part
, the dead short is fixed ,but if I swich the tv on the SMPT is pulsing and
if you switch it off the pulse goes slower and stop after a while. I think I
have a power supply problem to the SMPT . How can I test the voltage on the
SMPT and what is the voltage suppose to be

Thanks Walter

 

Hi Walter,

Since i do not have this Tv model details thus i don’t have any of the output voltages value. However the output has to be stable. You can take the filter cap as reference. If the output line has a 25 volt filter cap then roughly the voltage at that line should be around 14 to 20 volts. I suggest that you check all the components in the primary side and if possible directly replace the power IC and retest.

Jestine

 

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

 

HI Roger,

sir,i adjusted already,the fly back transformer.trimmer lower portion.the display become brighter,but there is horizontal line apper.i replace already the bad resistor,that change value.rated 22 ohms,but when i check using digital tester,it reads .7ohms,and i also found a bad hot transistor,no.d1651 npn type.today i bought a hot transistor.to replace the bad transistor.i already test a transistor,i found out that there is leak between base and emitter.and also collector and emitter.sir,maybe  monday i will confirm about what happen
after i replace bad components.and i will test the tv.thanks for advise.sir.have a nice day.

Hope to get good news from you. For your information, sometimes a too low resistor our digital meter don’t have the capability to test it unless you have a low ohm meter like the Blue ESR meter. If you do not plan to invest in such a meter, you can always directly replace the resistor and retest.

Have a good day!

Jestine

 

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

 

hi Jesine,

thank you for your quick reply.i  see one small 8 feet SMD IC marked U200  behind the power board. now, how can i test them? i feel very sorry for bothering you so many times.

 

Hi Ming,
No problem because i give support to my buyer. You will learn more by asking question. How to test the power IC?  Find the ic datasheet and locate the supply and output pin. Power on the monitor and test the supply pin with your voltmeter. For the output pin you need a scope to test it. If you can’t reach to the ic pin, you may need a wire to solder it to the supply and output pin but do it carefully.

Have a good day!

Jestine

 

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

 

Hi Bailing,

I’m thinking of faxing some potential customers, but recalling your post about “How to Get Customers?”, you recommended us to look for computer company. In my opinion searching for any company which use a lot of computer monitor is also potential customer. Also, I want to get first hand customer, not via third party, since they want the commission fee, what do you think?

Yes you can do that. Just fax to any computer company regardless big or small companies. In your fax if possible state the term and condition and pricing. If they call you that means you have the chance to close the deal.

Another important point is, when faxing to unfamiliar companies, usually we don’t know the name of the person who will receive it; so how should I write the name or title of the receiver? I’m afraid if we don’t know the exact person to write, the fax will go to someone else.

My side here we have a computer directory that have company names and contact person so it would be easy for us to attention to who. In your case, you can attention it to the manager. In your fax, remember to put some Monitor pictures because usually any computer company employees will put some attention when they see Monitors picture in the fax (related field).

About repairing LCD monitors, do you also find PFC circuit there?

No normally found it in latest and the big type of computer power supply.

Have you ever found bad NTC component when repairing?

Yes, it would usually crack. It  was hit by a surge.

Is NTC also used in LCD monitors?

Some model do not have so it depends on the manufacturers.

Jestine

 

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

 

HI Ivan,

 

I have this problem with two 37 inch LCD tvs. The model number for the LG is 37lc2d and the model for the Olivia is 337-B11. Both tvs has the same problem, the picture is perfect but there is flickering in the back ground. It same as if the lamp is pulsating however, the picture is bright. The inverters boards are all ok, the master and the slave. Can you help me with this problem. I have no schamatic on these sets. Thanks!

Assuming if all the output voltages are tested good then it could be cause by a piece of weak lamp.

Jestine

 

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

 

Hie

I hope my email will find you well,l have a problem with television
its not showing pictures on it and showing a very thin vertical line
on center of the screen and it had sound but now it just stopped
talking please h

 

 

HI Sinda,

Check the horizontal yoke coil area for dry joints and bad components. Make sure the horizontal yoke coil winding is not open circuit.

Jestine

 

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

 

Hi Jestine,

Thank you ever so much for you reports on SMPSs & LCDs which I found very useful,very practical,precise & to the point without the theoretical jargon which is hardly ever used by the repair tech.I managed to repair 3 LCDs with the help of just your short reports.I’ll be in touch with you shortly regarding your ebooks.

God bless & best regards

 

Sabir

 

South Africa

 

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

 

Message: if i will connect two capacitors in parallel, is the voltage of that capacitor will also increase or the micro farad only?

 

Hi Gil,

Please visit this link:

http://www.electronicrepairguide.com/series-and-parallel-capacitors.html

Jestine

 

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

 

Dear Sir:

 

Good Day!

 

Sir i am repairing now a hann-g lcd monitor with a display problem.  i’d checked the power supply and found 2 bulky e-caps.  my problem now is one of the e-caps is  not available in all electronics store here in our place.  its 680uf 16v.  i was thinking if is it possible to put 2 e-caps together in parallel connection. what i know is if you put 2 e-caps together it will increase the microfarad value. is it only the microfarad value will increase, or also the voltage value?

 

thanks you so much.

 

Gil

 

HI Gil,

You can put in a 1000uf 16 volt e-cap. So no need to worry about the parallel connection.

Jestine

 

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

 

HI Julianto,

Sir, it’s a samsung crt 15″, when I detach the data cable, the monitor show no signal, but when I connect to the computer the monitor become black and blank.Can you suggest which part is the fault?

It could be the fault of eeprom or cpu ic. Make sure the supply voltage is good and the B+ voltage to the flyback is good too.

 

The other monitor is cannot on.The relay is like switching on and off.The primary capacitor have voltage when turn on,but 0volt at secondary side. Try to replace the hot, but still the same. Check diode at secondary side, all okay. Is it possible the problem is at primary side?

You need to isolate the problem first by visiting this link:

http://www.scribd.com/doc/2957819/TT204-Identifying-television-SMPS-problems

It can be in the primary or secondary section.

 

How to recognize the vertical section on the monitor?

 

Look for an IC that is standing and attach to heatsink. The number of pins can be from 6 to 20 pins.

Jestine

 

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

HI Gopal,

Thanks for your reply regarding my previous query.

No problem.

Now i have one more question that most of the time you preferred analog multimeter instead of digital multimeter. But about 20 years of my experience, i have found that digital meter is best for onboard component testing as well as out of board. I feel comfortable to work with digital multimeter because analog meter has improper pointer deflection after using two to three months. I solve about 99% of the faults using digital meter only 1% is used for oscillation testing using analog meter. My question is what special benefit do you get in analog meter in comparison to digital meter. If i feel your justification is right then i will purchase a good analog multimeter. Waiting for your reply.

I came across many diodes that checks okay but fail when test with analog meter when set to x 10 k ohm. The reason for it is simple. The output voltage of analog meter is higher than digital meter. In fact you can test the output of analog and digital meter with another voltmeter. The output of digital meter when set to ohm range is about 0.4 to 3 volt but for analog meter it has 12 volt when you set it to x10 K ohm. Those small voltage of digital meter sometimes is not enough to check a leaky diode but using analog meter there is no problem in finding the bad diode.

Jestine
http://www.JestineYong.com

 

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

 

HI Diaan,

I am stuck on a monitor fault that I can’t seem to repair.

I have two Toei TC-V614H monitors that is used on Sigma Poker Machines. Yes, it is an old monitor allready. I dont have and wiring diagram for it.

The one that I struggle with had no picture because an 2,7ohm 5watt resistor that gone up in value to about 8ohms. It got very hot. Its situated on the neck board and is grounded as I could make out. After I replaced this my picture was restored, but still this resistor got very hot.

You must trace to see where this resistor line go because there must be a reason why resistor gets hot.

 

I had also changed many capacitors that have a very High ESR resistance and I got a very nice picture again, BUT WITH WHITE FLYBACK LINES accross the screen. Horisontal lines. I tried to adjust the bright and subbright so this lines can disappear but the picture color got worse. And still that 2.7ohm resistor is still to hot. My measurements on the G2 line is very high, about 305Volts. My Green Blue and Red are also high with 119Volts.So now I am stuck. So I took the other monitor and notice a very bad picture color and with a little black shaddow on the top left corner. I took the volttage on the G2  and it was lower than 100volt. The Red,Green and Blue Votages was also low. Much lower than the other monitor.  So I took my ESR meter and replaced allot of bad caps. After I was done I measure the voltages again and I got a great picture, but now I have the same problem as the first monitor. Same White lines that I cant get rid of and the voltages are also high as the first one and that resistor got hot as well.a

A weak tube, bad vertical IC and bad G1 voltage line could cause flyback lines.

I cant seem to measure any heater voltage.

If the heater voltage is from flyback then you can’t measure it because it is a high pulse AC.

 

 

Now I dont know what to do. Could it be that some of the capacitors that I have changed is giving me this fault?

If those caps are new, it will be very rare it can cause such problem.

And if Why? Its the same vallues as the old ones. I have checked that capacitor on the neck board accross the G2 line. The 2kV one, have replaced it but the G2 voltage remain the same.


As suggested above a weak picture tube could such problem. Try replace with a good picture tube and retest.

Jestine

 

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

 

HI Gopal,

Thank you so much for giving actual concept of analog multimeter. Now my question is

What other components can be better checked by analog meter other than leaky diode.

Transistor.

Can we identify the leaky diode or other components on board or out of board using analog meter.

You need to check the components out of board. It is not recommended for analog meter to check components onboard because of the higher voltage output from the probe.

Jestine

 

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

 

HI Noorishkandar,

Hello Justine..Saya ingin bertanyakan pendapat anda.Sekiranya untuk check Flyback,DY,Coil dan sebagainya jenis tester meter apakah yang sesuai untuk saya beli dan berapa harganya?

Blue ring tester dan harganya adalah:

Kitset ialah RM230.00

Siap pasang ialah RM330.00

Yang kedua berapakah harga DY294 Digital Tester?

Kamu boleh dapatkannya dari:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260607100672

Yang ketiga untuk check Varistor dan juga ceramic disc tester meter jenis apa yang perlu saya beli?

Anda boleh guna DY294 TESTER untuk check varistor dan ceramic capacitor. Untuk check nilai capacitor anda perlu digital capacitance meter.

Jestine

 

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

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2 Comments

  1. Buddhika

    December 28, 2011 at 6:14 pm

    Dear Sir,

    I have a LG CB553H-NA Color CRT Monitor having a problem with picture vertical rolling with extra height. I replaced the vertical deflection ic STV9302A.But the problem is same.Pl. help me.

    Likes(0)Dislikes(0)
  2. admin

    December 29, 2011 at 11:22 am

    Hi Buddhika,

    Vertical or horizontal rolling? Horizontal rolling you need to check vertical side and vertical rolling you need to check horizontal side. Have you heck the supply voltage to the vertical output ic?

    Jestine

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