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Electronics Repair Questions/Answers & Testimonials- Part 39

By Jestine Yong on December 3, 2012

Hi Jestine!

I have already launch my electronics workshop in my home town starting to work on lcd tv, lcd mornitors and so forth! currently i saw an advert onthe magazine about the short course on microcontroller at the dar institute of technology! my question is does this MCU course important to learn? and if yes why do i need it?

Thanks

Amri

Hi Amri,

Additional knowledge is always important. If there are such a short course in my country I will definitely attend it

Jestine

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I am a member of the lcd monitor clubap establish by Mr Jestine Yong,
and have learn more about monitors repear than i could imagine
now am reeping the fruitfrom my study through him,Thanks Mr Yong
Fr, Johnie Jones

British Virgin Islands

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special thanks and much appreciated love from you.It means a lot to me because Im learning so much interesting knowledge from such a good person that you really are.Thank you very much.

Mamosa

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Hi Yong,

I'm using Sony LED TV "(KDL- 40EX713) I Can't change sound system from I to B/G or D/K or L when operating in analoque mode. What should I do?"Because of this I only receive bad picture quality with noise.

BR.

Noi.

Ghana – Africa

Hi Ebenezer,

Try reset the Tv to factory default and auto tuning again. If still same problem, then try to update the latest firmware on mainboard.

Jestine

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Hi Jestine,

Thanks for this month's newsletter which has adversely contributed to successful troubleshooting and diagnosis. I would like to know whether I can Get ICs LM331 and MC14553 for frequency-to-voltage conversion.

Thanks,

Collins

Hi Collins,

You can get the ICs from this website:

http://www.utsource.net/

Jestine

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Hi Jestine,

A while back I sent you email below about a problem I had with an LCD screen.

I found a good deal for an identical used monitor on eBay that was dead but panel was not broken (most probably power supply problem).

I took the power supply from my monitor and put it into this one and monitor started working fine, so it was indeed a PSU problem. Then I took mainboard from my screen and put it into this one too and display was still 100% good, so we now know that the problem described below was caused by bad LCD panel. This has been bothering me for some time now as to which of the 2 it was (Mainboard/mcu or LCD panel) and now that I finally have the answer thought I would let you know too since I emailed you about this.

Thank you again for your very useful and informative web site and newsletter.

Philip

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Hi Luis,

Thank you for the newsletter about LCD TV repair. I will refer to it, I'm sure, when the time comes to repair one. Right now I picked up again the repair of Dell LCD monitor 1704FP that still has me stumped. After replacing the FET's you recommended in the inverter section and checking electrolytic caps with ESR and cap meters, resoldering areas that were questionable, I now have power indication but with a display that only lasts a few seconds. This monitor has SMDs on the solder side of the board two of which I haven't found datasheet information for and a third for which I have information that does not make sense to me. Maybe you give a hand with this and illuminate me on the third. The markings on the components are as follows:

On the inverter side of the board: I801 is marked SG6841SZ.

On the power supply side: I101 is marked OZ9930g; and, the third SMD, Q804 is marked FOD 13N06L.

The information I have identifies 13N06L as an N-channel 60v FET logic level. My question is, what purpose does a logic level FET serve on this board and is it likely to cause the monitor to have shutdown problem? In your LCD monitor repair ebook, you mention several inverter ICs with numbers like OZ960, OZ962, OZ965 so is OZ9930 the same type of device? I could not find any information on it. You have also mentioned a part cross reference book by Philips, I believe, is this reference available in the US or is it a British publication?

The power ic is SG6841Z and the inverter ic is OZ9930. First, have you replace the backlight because if one of the backlight have problem it will cause shutdown problem. Try compare the resistance reading of the high voltage transformer. Both should have the same ohms reading. OZ9930 is the inverter ic and the function is the same as other OZ series IC. The Philips ECG is no longer in production and taken over by nteinc.com. You can get the NTE book at sayal.com

Lastly but not least, what specifications or characteristics would you look for on an oscilloscope and a microscope for general electronics repair or at least for monitor repair? Sorry for the long email but these are questions I need to find answers for to improve my repair skills and capabilities. You have been a good teacher and I am grateful for that. Thank you in advance for your help. With best regards,
You can get either an analogue or Digital oscilloscope with at least a 100Mhz so that you do not need to upgrade it again.

Jestine

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Hi Gopal,

I have one more question,is that what modification is required in yoke if i connect CTV kit in CRT monitor. I think H-yoke needs some modification to adjust the TV kit.

I have not done this modification before but checking the yoke coil inductance value is very important for the Horizontal yoke coil and resistance in vertical yoke coil. A wrong spec could instantly kill the HOT.

Jestine

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hi jestine
I received one power supply computer that primary transistor burnt
also varistor burnt ,I replace this component and check another
component in primary and secondary sides and only found one diode
shotky and one 100 ohm resistor burnt ,I replace these component and
also ic tl494 and lp7510 and plug in power cord but the power supply
do not start ,I place frequency meter in trans secondary side and show
me 31 kHz and another show 3 kHz and then place multimeter and when i
start power supply in out of 12v show 68 mv this may the switching
trans failure or you think another component failed !regard to that I
check all component!
I wait to reply
have a nice day

Hi,

I suggest that you check all the components in the primary side since you found the burnt transistor and varistor. If this power supply is using power fet and power ic you may need to directly replace the power ic and retest.

Jestine
http://www.JestineYong.com

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I wanna repair 12v dc powersupply it's transformerless one.tell me what should I need to check for repair.

Janaka

I suggest that you check all the components in the power side. Check for shorted secondary diode too. If the power side is using an IC there the IC could have problem if all the surrounding components are tested good.

Jestine

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Dear Mr. Yong,
Now I need a personal assistance: I have 2 laptops with a commom lcd problem – the screen when is on, it is divided in 3 parts by vertical lines. What is the problem and how to solve it?

Warm Regards
Augusto

Hi Augusto,

Most likely is the LCD panel and it can't be repaired.

Jestine

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Hi Jestine, thanks again for this month's newsletters.

I am still struggling to find the quotation for the latest NTE 14th edition book.
I tried on several occasions to contact Sayal electronics to send me the pricing of this book to no avail.
Can you send me just a roughly estimation how much you bought the book, just as to be able to balance my Start-up Worksheet for a business plan?

I will then place a direct order to them.

Have a fantastic day, bye for now !

Johannes

HI Johannes,

Mine is an old version. I did not get the latest edition from them. One of my members also told me that they seems like don't want to sell to him (asia country). Try here:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=500-075

Jestine
http://www.JestineYong.com

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Hi Jestine

I have enjoyed reading your articles. I was wondering if you know a solution to the Samsung SyncMaster 710V "out of range error"

any input would be apreciated

Thanks

Steve

Hi Steve,

This is a coon fault and the problem is corrupted Microcontroller Unit (MCU).

Jestine

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Thanks Jestine, this email was right on time, my own LCD monitor goes blank after about 2 or 3 minutes, not one seconf. Although I do not have components to swap out it lays out a good path for me to follow.
I do appreciate these emails and read them all. Keep them coming!
Donovan

Hi Donovan,

Hope you could locate the problem soon. Check the e-cap first and if they are good then check on the backlight.

Jestine

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Jestine,

As always I read about your email: LCD monitor "repair mistake".

My observation was that you were helped greatly by being able to access components & board assemblies from an identical working monitor. This helped you pin down the problem area but you don't advise how that might be economically achieved if circumstances where another monitor was not available.

I would have been interested to know also (perhaps from the age of the monitor) whether the solder used in production was lo-lead & whether you have found this type of solder results in more faulty joints.

Certainly a soldered IC, where heat is not a factor, would not have been an area I would have suspected to look for a faulty joint.

Thanks as always,

Peter

HI Peter,

You are right. If I do not have a similar monitor for comparison then I will use other troubleshooting method to work on it. However, currently I don't have similar problem with single monitor otherwise I could write another report on that. Thanks for the input.

Jestine

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Hi Jestine

My question is – do SMPS have to have a PWM controller IC to operate? I know that there are combined Mosfet/PWM controllers but I have two small SMPS which appear to have just a Mosfet. In this case what component supplies the mosfet gate to provide the switching to the transformer primary side?

Hey, brilliant article on the LCD repair by the way.

Kind regards

Robert

HI Robert,

Not necessary to have a pwm controller ic because designers could use common components to form an oscillator circuit to switch the mosfet.

Jestine

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Sir Yong.I am looking for 2SC3927 to no avail. Is there any substitution for this? Thanks

Hi Corriete,

According to my databook the equivalent number for 2SC3927 are BUV47A, BUW12A, 2SC3637

Jestine
http://www.JestineYong.com

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Dear Mr. Yong,

Thanks for this informations, now I am just fixing the same model : Samsung LCD 19" Monitor SyncMaster931BW and Try to rewarm

the Inverter IC solder but unfortunately the monitor is still shutting down after 1s.

But I discovered that one of the backlight was turn off during the start process.

So I investigate the backlight transformer and I found that one of the both coil on the secondary side was open !

So I replace the transformer ref: TMS91429CT and solve the problem.

Best Regards.

Vincent.

Hi Vincent,

Congrat! It is very common for Samsung 19" model to have a fail high voltage transformer.

Jestine

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can you advice for the following problem. LED TV and satellite receiver Grundig40vle7131bf Dreambox800hd occasionallyencounter problems while watching the action on screen appearance of horizontal lines which is up slightly distorted images(such as celery snaps electrolytes in the vertical at the old CRT). With the change of personnel, the line moves all more up and disappear.To happens on hd and sd signalu.Receiver is set to 1080i.Grundig is 100Hz and Full HD .. no problems if thereceiver is set to 720p.Moze any advice for this problem.Thanks.

Hi Benjamin,

It could the firmware problem. Try update the firmware and see how it goes.

Jestine

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Hello,

sir,i hope you will be fine.

i have a problem with my dell laptop n4050 whoes mouse cursor moves automatically….after about half an hour after starting…….what is the problem??

kindly send me the solution of this problem….

thanks.

saad

Have you try use other mouse? I have a notebook that have the same problem. After changing with a new mouse the problem solved.

Jestine

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Hi Mr. Yong
Good Day
Thanks for the news letters. I really appreciate it. By read about Samsung LCD in this weeks news letter. I also came across a Samsung LCD monitor 2233SW with the about same fault (Monitor goes on standby after some seconds with full view of the CPU)but was unable to repair it but luckily the monitor is with me so will try to solder the inverter IC. and will get back to you after that.
Once again thanks for sharing your powerful electronic experience with us. You are a true master of electronics
Thanks

Hi Imraz,

You are welcome. Check also the high voltage transformer and the backlight because Samsung 22" very frequent have these parts problem.

Jestine

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Hi JestineI had a Tv JVC whose model is AV-14FMG3B,it have power but no picture and sound,the power lead is blinking.that's all its symptom.but the power is ok . So what can be the fault,helpe me plz what to check or change thanks.

Hi,

If the output voltages are good then the fault can be the MCU IC because power LED signal coming from MCU IC. If fluctuates then you need to isolate it to check which section is giving problem ie the power or the mainboard/high voltage section.

Jestine

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My Samsung television was not powering on. I replaced 2 capacitors w/ slightly higher voltage. I plugged everything into the motherboard before screwing everything back in to see if the problem was fixed. I was able to turn the TV on and off. When I went to put the motherboard in place to secure it the tv went of and will not come back on. Did I possibly short something out? Thank you

Hi Heidi,

Yes and you need to double check the board make sure it didn't touch anything. Check for broken circuit tracks also using magnifier glass.

Jestine

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Hi Jestine,
Thanks for your help.When I checked,it was the 100microf capacitor for the vert output which was dry.After changing the lines went!
Thanks Jestine.
Jordan

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Dear Mr Jestine, I received a Sinotec tv :MP-32LCDSP (backlight shut down) yesterday and I remembered your recent19"LCD monitor e-mail tip. I went straight for the inverter IC, re-soldered and the problem was solved.
Thanx for sharing the info
Vusi

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Dear Mr. Yong,
My name is Houssein, and I’m from Morocco. I did come with your website a long time ago, and I find it amazingly useful. I’m an amateur electronics hobbyist and I need some of your assistance, can you please Sir help me with this?
I have being lately working on a friend’s LCD monitor (Belinea 101903) that have some backlight issues, the problem is that when I turn it on the display shows up for just 2 seconds and then shut off with the green LED blinking twice and then goes amber. I can see the display with the help of a flashlight even though there is no backlight.
At first glance the power supply unit (LIEN CHANG AI-0100B) doesn’t have any burned component, I took some voltage measurement and here is what I got.
The 12V connector:
When the power is off, in the 12V connector it reads 15.67V.
When the power is on, in the 12V connector it reads 13.79V (the CCFLS light up).
After 2 seconds, when the LED gets amber, in the 12V connector it reads 16V (the CCFLS are shutdown).
The on/off signal goes as following:
Power off: 0V
Power on: 3.08V
Amber LED: 0V
Readings on the BIT3193G inverter IC VCC pin:
Power off: 0.23V
Power on: 7.23V (CCFLs are lit up)
After 2 seconds, amber LED : 0.23V
The 5V connector reads all the time 5.01V.
I even tried some other 19” CCFLs on the power supply but with the same result.
Please Sir, accept all my gratitude for helping me solve this repair.
Sincerely yours.

Hi Hossien,

If you have replaced with other backlight and still shutdown then check on the high voltage transformer. The resistance winding has to be the same between the top and bottom backlight.

Jestine

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hi Mr jestine,

i recently got hold of your book. i am very interested in electronics and and got a soniq lcd 26" tv stuck in standby mode. upon checking the smps using your method i found out the filter cap is giving out 338vdc and the power ic (ice3b1065) at pin 7 only produce 12.3vdc your booksays its shold be 300vdc and 16vdc i checked the bridge rectifier on cuirit and its is ok incoming ac 240v(diode check using digital multimeter)i tested the cy capacitor in x10k at primary before bridge rec and the needle move slightly i test the power output diode (schkotty) and it has no reading. as well as the pins at the end of board where you join the wire to the other boards

i dont have esr meter or lopt or even the meter to test the dielectric. (budget issue)

i have not removed any component yet to check all is on board

i have 2 transformer on board crossing to secondary. on the board it says T1,T2 (havent remove it like it says in your book)

i am stuck from here.pls advice

thank you in advance!

Hi Steven,

Standby modes means the standby power supply is working and the main power supply is not working. The CPU will get the 5 volt standby volt in order to function. It will send a signal to an optoisolator ic circuit to trigger the primary side so that full output power will be obtained. If the CPU is not working or the signal can't reach the optoisolator ic then there will be no output voltages. Sometimes a bad EEPROM IC could cause such problem too. I suggest that you try search for the schematic and see if the CPU is sending out an On signal or not.

Keep me update on this.

Jestine

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8 Comments

Imran

December 4, 2012 at 4:25 am

Hi Justine this Imran hope you remember me I posted one question regarding Xbox psu burnt component and was confused about thermistor and varistor well I was not able to find whether it was in series or parallel so I replaced the burnt item with 250 v varistor and switched on but it didn't work it didn't turn on so I removed it and replaced with piece off wire and switched and my inverter backup of my home fuse blown may be the wire was not good idea which I thought will work my question is does I have to replace with thermistot or a different varistor will work please help

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- Jestine Yong
  
  December 4, 2012 at 7:08 am
  
  HI Imran,
  
  First you need to know what type of component that already burnt. If it is a varistor (you can see from any varistor circuit how it is connected) and you place in a thermistor definitely the main fuse will blow.
  
  Jestine
  
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Imran

December 8, 2012 at 7:07 pm

Hi Jestine thanks for your info I am a novice in electronics the problem is there is no number on the blown component it looks like varistor or thermistor http://img708.imageshack.us/img708/4097/1354927130032.jpg
the green component beside heat sink is the one blown , in one of your post hp laserjet you replaced a varistor but you said we can solder a wire but it will not protect from future surge that's what I did I removed this component and soldered a wire and switched on the main fuse of our house went off . I then replaced it with 240 v varistor and switched on this time fuse didn't blow but PSU. Didn't get on plz help me as I have been following you a very long time you are genius in this it will be a cup of tea but for me a ocean

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Reply
- Jestine Yong
  
  December 10, 2012 at 8:00 am
  
  Hi Imran,
  
  Sometimes the burnt component can be a varistor or thermister. A thermister is connected in series with the live line and the varistor is connected in between live to ground or neutral to ground or live and neutral. You need to find out what type of component before you put in the component to avoid problem.
  
  Jestine
  
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Zibbo

December 11, 2012 at 9:45 am

Hi Jestine
I am repairing a Sanyo TV Chassis MC41B, it has a shorted transistor TKD2092 and according to the schematic it is a Darlington transistor. I cannot find the part in Zimbabwe where I am so I searched for the datasheet on the internet and I could not find it. All i am getting is TKD2092 NPN Transistor. Can I use this ordinary transistor to replace the Darlington?
Is it normal to have the same part number for different parts? Thank you very much for your time and your articles
I

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- Jestine Yong
  
  December 12, 2012 at 7:13 am
  
  HI Zibbo,
  
  I have no encountered such situation before. if the original part number is darlington then you should use back darlington. In your case if you have no other choice then you can try replace and retest.
  
  Jestine
  
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gilbert

December 2, 2013 at 6:42 am

hi its gilbert again after a very long time how are you keeping can you please help me with eeprom data for sinotec lcd mp-32hu32 or rc-n38

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- Jestine Yong
  
  December 2, 2013 at 3:13 pm
  
  HI Gilbert,
  
  I'm fine but sorry I do not have those eeprom data.
  
  Jestine
  
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