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Electronic Repair Questions/Answers And Testimonials -Part 40

By Jestine Yong on September 27, 2009

Hello Jestine,

Thanks again for another well-written and well-illustrated article.
I appreciate your time and effort to do this.

Regards
Toby

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

Hi,hope all is well?.I said it and i well say it again that you’re truly a heaven’s sent.I’ve gotten ur books and can’t stop reading them..May God bless you.

Rexford A

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Hi Jestine, am so happy for the work you are doing for God, i want you to know that this training you are giving us online is a great one and i believe God is happy with it. you may not know how great you have imparted on people possitvely, you are making peopl’s dreams come thruogh in life, am a living witness because this what i want. may God countinuely belss you and your family and give you more wisdom to enhance is kingdom.

Ehis I

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

hi mr jestine yong

i have a problem with crt monitor type vision 15″ and the problem is the horisantal line appaere in center of monitor also some lines Appear after a period i need help this problem thank for ur patience…..

have a nice day

Hi Bashar,

Check the vertical output ic for dry joints and make sure have supply voltage. Hope this helps!

Jestine
http://www.JestineYong.com

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

HI Derek,

I’ve not short the probe and press the on/off button.

Yes you should short the probe and press the button again to reset the microcontroller.

What i have did is to replace the 2 crocodile clips with metal testing probe (those used in multimeter). Will these have any effect?
It will have effect if the probe is too long. Try make it shorter to about 30cm.

How can I re-calibrate myself?

Please visit this link for the procedure at:

http://www.anatekcorp.com/BlueESR.pdf

Jestine
http://www.JestineYong.com

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

Dear Mr. Jestine,

Thanks for the monthly repair guide and as you said its very important to check for those labeled voltages on the board first to have a better approach where to start with a problem.

In fact may be you can help me with one Sony Tv model KV-XG25M80 with the standby led blinking twice. I found the HOT faulty and replaced it, however the problem stays the same.

Also, once it goes on standby i can’t find any voltage i would checked for.

Can you please help me..?

Many Thanks,

Regards,

Vinaye

HI Vinaye,

Does the tv smps have the optoisolator ic? Sometimes a bad CPU may be the cause of the problem.

Jestine
http://www.JestineYong.com

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

Hi Jestine,
a question on HP / BENQ 17″ LCD HP L1706

Powers up for about 6 seconds and display looks fine. Hissing sound from power supply and then display goes off.
Un plug back lights and no hissing sound and obviously no display.
Could the lamps be at fault.

Regards,David H
Senior Technical Officer

HI David,

it could be the lamp or the power supply problem. Please make sure the filter are ok and all the output voltages are within spec. Have a good day!

Jestine
http://www.JestineYong.com

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

Sir,

I am one your members in Papua New Guinea. I’m repairing a 15″ Able Veiw monitor.

I can hear the high voltage and feel the static but when I looked closer there is no glow at the cathode ray guns.

The flyback internal capacitor measurs 2.4nf and I get 375V at G2 then it started arcing to ground. I removed the G2 line and measured voltage – nothing near what I expected ie. 0.4v.

I suspect the flyback might be playing up and I don’t have a similar type to change so I decided to get your advice first.

Thanks for any advice you have.

John

Madang – PNG

HI John,

Yes the flyback could be at fault because the G2 is not suppose to arc to ground. I believe after arcing to ground the monitor shutdown thus the voltages all gone down to zero volt.

Jestine

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

DEAR JESTINE

thank you so much of reply but let me ask you in this way:

when you open a lcd monitor or dvd player or satelite reciever .etc… mainly you have two board

1- is main board that is completely is coverd with smd parts

2- the power supply that is not made with smd parts and is made with classic electronic

parts

my question is why manufaturere are not making this board with smd components?

thank you of reply in advance

beh

HI Beh,

There could be few reasons. First the smd parts is more expensive, second-there is space for bigger parts and third the design of smps using smd could be complicated.

Jestine

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

Hi Jestine Yong !
I do repair LCD SyncMaster 740N
The Monitor start and through 3-5 seconds is switched off but scene and 5 Volts there is.
14 V for invertor is:
– When monitor out-of-work there is 15 V
– When screen works 13 V
– When operates protection there is 19 V
What is it ?

Please send me data sheets for IC BIT3195

Best Regards,
Saprikin Victor

HI Victor,

Samsung 740N have common fault of bad MCU. That means if all the output voltages are good then suspect a bad MCU.

Jestine
http://www.JestineYong.com

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Hi Jestine, Thanks for your newsletter. Question is better than answer. I need to ask you where to put the black probe of the meter when testing voltage. The red probe goes to the voltage connector.
Hope to hear from you soon.
Regards,
john

HI John,

The black probe should be put to the cold ground which mean the casing (earth ground) of the equipment assuming if you are checking the secondary side. If you need to check the primary power side your black probe should be put to the negative pin of the big filter capacitor. Hope this helps!

jestine

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I am so much intrested to know how to get from your web site ,example a componenent which is equivqlent for replacement C5208 transistor for switchig a computer monitor epro Model 775A.

Hi Opiyo,

From my databook the replacement for 2SC5208 are BUX99, BUV63, 2SC3682 and 2SC3840.

Jestine

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Hi Jestine, this is Dalton from New york, I am studying electronics technology with cleveland institute of electronics I do it correspondently , I would like to get into cell phone, ipods, xbox and ps2 repairs, do you have any websites, books or any other information that would be useful in that area.

Thankyou
Dalton

Hi Dalton,

I’ve heard of Cleveland Institute of Electronics. As for the books sorry i do not have any title on those books.

Have a good day!

Jestine
http://www.JestineYong.com

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

ok . I’m going to remove the flyback transformer and will replace with the nearest substitute that came from another able view monitor but is a different model. After removing the faulty flyback I measured the internal capacitor but got an opened reading (The needle didn’t even flick). Please point me to a place I can get schemetics for my flybacks.

Your advice is much appreciated.

John

HI John,

Sometimes the capacitor value is too small for the meter to register a flick. You need a capacitance meter to test it out. As for the flyback diagram you can try http://www.hrdiemen.com

Jestine

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

Hello! good pm I hope you are always in good health and of course in good mode upon reading my email.
I just hope that you will always be patient upon reading my email that I think It is always about electronic repair. You know my problem about the sony tv that I had already replaced the fly back and the 1.2 k capacitor is still going on and my question is why is it that the tv will only operate for one hour under normal condition but after you shut it off then you put it on again it will not operte anymore because the HOT had already blown up. If you have any other idea about this please send it to me. I had already check the SMPS and it is very normal.

HI Tito,

Please read my blog post here:

https://www.jestineyong.com/?p=403

Jestine

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Hi Achour,

hello mr jestine, how are you.

I’m fine thank you.

i like tell you if you can help me to solve two monitors problem. the first monitor: when the vga cable is disconnected from the pc, the monitor power on and a raster appear ( the THT start up and there is light on the screen). but when i connect the vga cable to the pc, the monitor power on for about 1s and then power off ( the led become green about 1s and then retun to orange, there is no raster). is this a problem of eeprom or THT?

It could be eeprom or defective CPU.

the second monitor: the monitor power on normally but the image is shifted horizontally. ther is a vertical black bar ( about 1 cm horizontally and keep tentire vertical size) on the left of monitor. we can move the image horizontally to the left or to the right but the bar does not disappear.

thank you mr jestine.

Try replace the horizontal and vertical oscillator ic and retest the set. If it still bad then i guess you need to check on the corresponding components to the horizontal ic.

Jestine
http://www.JestineYong.com

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

Jestine

Great to hear from you all the time you shareing the knowledge with others

Am reguesting you to help me if theys a way on how to TEST an IC”s or simple way of building up ONE TO TEST any type of IC’s.

Sorry for the trouble,thank you for the help

Best Regards

Patrick

HI Patrick,

The best way to test ic is to understand the ic pin out first then use scope to test on the input and output waveform. make sure there is voltage entering the ic too. Sorry there is no simple way to build a tester for ICs.

Jestine

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

Hi jestine

…… as i told you my friend he have tv repair shop.. since 30 year s so far .

he said most of the recent sets are not repair able due to tomuch little smd parts

that the manufacture used to make the set or even you found that part in side the

circuit you can not find anywhere that size and shape to subsitute them

sepcialy in cheaper sets

this means that work from now requier special equimpent and knowledge.

and investment.

thnx&rgrds

beh

Hi Beh,

You are right that one need to have some specialize tolls and equipment to deal with SMD repair.

Jestine

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

Hello Mr. Jestine Yong,

I have read all of your books and they are very good. Congratulations!

Do you have any documentation on the CRT Monitor that you can send me? Or links with useful tips on troubleshooting this type of equipment?

Thanks for all the information that you shared.

Best regards,

Bruno

HI Bruno,

You are welcome. Please visit this link:

http://www.repairfaq.org/sam/monfaq.htm

Jestine

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

HI Gordon,

It’s great reading your articles.

You are welcome!

I wish you could come to Nigeria for some training in electronics as you did for those in Asia!

Hope i have the time.

I have unfading interest in electronics but can’t find a good place to train here in Lagos, Nigeria. As a Computer Technician, I am particularly interested in computer peripherals and accessaries like CRT and LCD monitors; Laserjet, Deskjet and Dot matrix printers; UPSes,
stabilizers and Photocopiers. Could you please, educate me more on how to repair CRT monitors and UPSes.

I want to have insight (through elaborate explanation in texts and diagrams) on the subcircuits or stages that make up the main boards and the verious components found in these circuits. I would also be pleased to know about the common faults like no display, no power, short ciruit, etc and their solutions by going straight to faulty component(s) in a subcircuit. Finally, an understanding of what each component does in a subcircuit, how they are linked within the circuits and how best to test them will make my joy complete in this regard.

Start with my ebook first testing electronic components

Once you are good in testing electronic components in fact you can start to repair many type of equipment. You may visit this link for more information:

http://www.repairfaq.org/sam/monfaq.htm

jestine

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HI Stephane,

I have a Sanyo AVL-279 LCD TV with no image and no sound. The power light (red) is lit when the TV is plugged in and the power light turns to blue when the power button is switched on, but there is no image and no sound. So I opened the back panel to investigate and here’s what I found.

When the power button is switched on, there is a repeated and steady “ticking” sound coming from one of the power supply’s component (see the attached image). Problem is, I’m not totally sure what is this component; a coil/inductor or a transformer? I searched for it’s number (BCK-100-02 B1) on the Internet, but no result came out.

So, my questions are:

1) Is it possible for you, given the attached image, to know what is this component?

That is a switch mode power transformer

2) Is this component and it’s “ticking” sound is familiar to you and could be the cause of the problem?

SMPS transformer rarely have problem. It could be due to bad caps or faulty components in the power section that had caused the sound.

Also, for a simpler solution, I tried to search on the Internet for a power supply unit replacement, but I could not found any. Do you know an online store that sells this particular power supply unit?

Sorry no information on that power supply replacement.

Jestine
http://www.JestineYong.com

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

HI B,
I still repair monitors though not too often, instead I have more chinese students,

Good to hear that. More students means more income!

anyway repairing monitors could add some earning to my family. Hope that your business is also doing well.

During this ramadhan period, my repair business is a bit slow and will pick up after Hari Raya.

The problem of this monitor is dry joint, sometimes need to pat the cover to let the display appear. It looks like simple problem, but after resoldering some dry-joints, and reassembled the unit and power it on without signal, after about 6 seconds the display only show one bright point in the middle of the picture tube and the led then turns to amber color.

This monitor is manufactured in March 2000 and I found no burnt component inside and I have rechecked all the cable connection. What do you think could be the problem. I just don’t want to make the problem even bigger. Hope you could help me out with this problem because the owner is a new customer to me.

I guess you may have forgot to connect the pc tube yoke coil.

Jestine

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

Dear Jestine,

Thank you. I have read your report.

I have a problem on my hand with a baby monitoring LCD screen by Bosieboo 5.6`’ wireless.

The monitor was dropped accidentally and the only physical damage was on the stand and the power cable socket wire.

I managed and repaired the broken stand and the power jack, but the monitor doe not latch on the signal from the camera.

Can you suggest the solution so that the monitor comes back to it’s former self?

I will wait for your kind reply.

Yours Sincerely

Arjun C

HI Arjun,
If it had dropped then i guess it could also have broken the circuit track or may have some loose parts in it. I guess you need to open up the lcd to check it.

Jestine

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i have a L19ns-7 with no power issue i have done the testing you have told me, high voltage cap filter is fine with 120 volts and the rectifier is good also the power fet seems to test good but when i test the power ic fan7601 i get 0.3 volts on vcc pin i am lost it seems like a primary power problem could you send me some info or recommend what i do next.

Hi Chris,

Try remove the power ic and retest the vcc again. If the voltage back to normal then the ic is at fault. If it still low then i guess you may need to track it backward till you found the bad components.

Jestine
http://www.JestineYong.com

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

Dear Jestine,

Thank you very much for this month Repair Newsletter. I really don’t know to be grateful to you. Many advises retain my attention, mainly this:

“

The next solution for this problem is the training/servicing manual and schematic diagrams. With the help of these manuals and diagrams you can easily locate the test points because it usually show you what are the voltages, signal and etc at those points. There was a ERG member who said this “One have to spend some money in order to make money”. I totally agree with him. If the manuals or diagrams that you are seeking could help you to solve your problem then why not invest in it and when the problem solved you could charge your customer and you can keep the manuals and schematic for future reference too. It will pay itself back!”

Have a very nice day !

Leon A

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

HI Guy,

Thanks once again for more infos. Very interesting and highly informative.

No problem.

I would like to ask a question. How do you precisely identify a s/c resistor?How do you test a s/c resistor in circuit?

Resistor only develops open circuit or turn into high ohm. I have not seen a short circuit resistor before.

If the resistor is fried then it’s easy to see, excess current flowing through. It’s also easy to tell
when it’s o/c. I am busy repairing an old Telefunken TV Thomson Chassis
TX92F and I came across a web site offering repair tips relating to exactly
the
nature of the symptom I am faced with. It talks of s/c R274, 180k.? But when
I take a resistance reading, I get exactly 180k? So, again what does it mean

when it says short circuit? Please advise.

I guess he meant that short circuit elsewhere that burnt the 180k ohm resistor.

Have a good day!

Jestine

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

Hi..Jestine

Good day..It’s realy fun..I’ve learn lot of things on you and thank you by sharing your knowledge on us.

Renente D

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

Hi Jestine,

I have a problem with a LCD power pack module. I checked the output voltage and it was ok (12V), but I tested it with a 12V light bulb and it blinks.

I already replaced the electrolytic capacitors at the secondary side, I still have this failure “light bulb blinks”

What’s the next step on this troubleshooting??

Thanks

I already fixed more than 10 power supplies like this just replacing the output caps, but today it didn’t work…

HI Renial,

Check the primary side components especially the low ohm resistor and if possible direct replace the e-cap too in the primary side.

Jestine

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

Hi Jestine,

I hope you are keeping well. Your repair tips have helped me greatly and am very thankfull to you.

I have a situation here. My CRT TV displays only a thin horizontal blue line across the screen when I power it. I see nothing else but only the blue line on the black backgroud. I would be gratefull if you could provide me with tips on how work around the problem.

Thank you.

Regards

Martin

Hi Martin,

Check the vertical output ic section for dry joints and good supply voltage. If the supply voltage tested good and no dry joint direct replace the vertical ic and retest the set again. Hope this helps!

Jestine

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

Dear Jestine,

I’ve replaced the LM1279N ( RGB Video Amp ) in the CRT board, but still the same. This is the only IC in the CRT board, other parts are using discrete transistors.

I did measure & compare the voltage at CRT socket, and I got R & G were both 55V, but B is only 5V. I had difficulty in finding the culprit in every repair that needs board tracing and analyzing especially without schematics. Every time I tried to trace the blue ouput from the LM1279N IC I got lost.I would appreciate if you could give some hints how to solve this bluish display and soft horizontal retrace line. What components should I concentrate on, as the CRT board is big enough and contains lots of components. The signal cable has been checked to be OK.

In your reply, you also mentioned about comparing the RGB signal, do you mean using the scope?

Now, there should be no dry joints anymore, because the display get stable even if I shake it hard enough.

Have a great day. Thanks.

Bailing

Hi Bailing,

Yes you should compare it with scope but B have only 5 volts means there is something had gone wrong with the Blue circuit. Since this board do not use CRT driver IC then you should concentrate on the Blue driver transistor. Remove it and test off board together with all the corresponding components. Is the Blue signal coming out from the LM1279N IC good?

Jestine

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ok now i cant seem to read this reading. i have a mbr10100ct and i do the testing you recommend x1 black in the middle = no reading. red in the middle i get 15 ohm reading. now @ x10k black in middle i get a 2kohm reading for left and right. now reversed red in the middle i get a 1ohm each side. Are these readings correct as i am new and need some reassurance.

HI Chris,

Yes the schottky diode is good as it should have some leakage resistance but in your case the 2 kohm result would be a bit too high. I suggest that you compare with other working schottky diode to see the result.

Jestine
http://www.JestineYong.com

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

Sir i am having a problem on how to repair Horizontal and Vertical problems in Monitors and color problem. please sir i want a picture and practical way to solve these problems . what are the component responsible for it. And sir am also having problems on how to read some component like transformer, Anod Cap, IC’s and some others. i will be fulfilld if i have a picture Explanation of these problems thank you say.

Sorry i do not have picture for it-as for the Monitor problem you can refer to this link:

http://www.repairfaq.org/sam/monfaq.htm

As for the components, transformer printed code only be understood by the manufacturer, Anode cap have no code and IC’s have too many code. You can key in the ic part number in google and you will find all the spec there. Hope this helps!

jestine
http://www.JestineYong.com

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

HI Ting,

I own the above CTV. Recently.. a thin horiozontal line appears in the middle of the CTV after few hours of watching it. I suspected dry joints and resoldered one big brown coloured condenser. It worked fine for l whole day. Suddenly the CTV went blank, but sound is good. I switched the mains off for a

couple of hours and switched it on again. It works fine and later after a couple of hours…blank again.

I guess you try resolder on the vertical output ic area and retest the set again. Check also for dry joints in the CRT board.

By the way…why are some big condensers coloured blue/white…some are brown/white..some red…?

Different manufacturers produced different type of color. As long as the value is correct then it will work. Have a good day!

Jestine
http://www.JestineYong.com

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

HI Jim,

Jim here..hope u fine there..

Thanks and i’m fine.

Thanks 4 u r current newsletter.so,which component i should replace if a motherboard is dead.?

This you have to check. It can be a shorted ic, cap , transistor and etc. Have you visit this link before:

http://www.elstonsystems.com/prod/pc_post_diagnostic_card.html

Is the checking method of mosfet is same aslike of Ordinary(monitor) mosfets??

Checking mosfet is all the same but first you need to find out if the mosfet is P or N channel

Where r the main voltage check points in a motherboard??

At the power supply connector, crystal, pci slot and IC vcc pin

Jestine
http://www.JestineYong.com

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

Hi Jestine,

Thanks for the reply.

Going back to the 17” Philips lcd monitor, the green light is ON, and the screen TURN ON for 2-3 seconds and NO DISPLAY after that. From my little experience, ecaps 470uf, 25v and 220uf 16v are leaking and this inverter transformer, IT-E19-NB4004B, was faulty once.

I was reading the first ebook that I bought from you last night, TESTING ELECTRONICS COMPONENT, using a insulation tester to test the high voltage ceramic caps for leakage. I’m gonna do this next to all the board.

Still, what confuses me is what or which component do really cause this shutdown. I did an experiment last night, putting the backlight connector one at a time to try to eliminate which side of the inverter circuit is faulty, but both of them work for this particular panel. Maybe you have something that can help me resolve this problem. Any response will be highly appreciated.

Thank you very much again Sir

Regards,

arvin

Hi Arvin,

Shutdown could be cause by bad back light, bad inverter board and bad Mainboard. Ok tell me the result after the Monitor shutdown. Is the supply voltage still going to the vcc oin of inverter IC? Sometimes you can compare the resistance reading between the top and bottom circuit using x 1 ohm range. Any differences could lead you to the cause of the problem. Hope this helps!

Jestine
http://www.JestineYong.com

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

thanks for replying

the inverter is tested working fine

just that the motherboard not sending the signal to switch it on.

wondering where to find the pin out for notebook inverter to check

power and on / off signal

if you have any lead on this do inform

thanks

Hi Henry,

The only place you can find out is from the connector of the inverter board. The motherboard should send the on/off signal in one of those wire in the connector and you need to find it out. The on/off signal should have few volt when on and zero volt when off.

Jestine

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

Hi Zed,

i would like to ask a question i got a shorted zener diode near a vertical section it has no part number. on this location there is a near same diode and i test it good. i measure it thru zener diode tester you have share with us and it has 8 volts so i decide it to change the shorted diode with a rating of the same volts and i change vertical ic but it has no effects. This tv has a one horizontal line across the monitor of tv. is the one that i found short was a switching and not a zener diode that’s why a tv is remained it one horizontal line? thank you sir. God bless you more.

I guess you cannot assume the value to be the same and you need a schematic to locate the exact voltage. What is the board location marking a “D” or “ZD”? Sometimes a diode without marking could be a normal diode 1N4148.

Jestine

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

Ya sir.i’ve little idea on tat motherboard pci testing card..what ‘ll
be the prob if capacitors in power supply area keep bulg’s every month
after replacing it.At which condition capacitors heats up itself?

HI Jim,
Try get a good quality cap and get the one that have 105 Celcius and make sure the fan is working well.

Jestine
http://www.JestineYong.com

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

Your Name: Sampath Niriella
Message: I have a CRT tv 21″..now there only a bright horizontal line on the middle of the screen.i changed the vertical IC but the problem hasn’t changed..i hope ur help..

Thaks..!

Hi Sampath,

Have you check the supply voltage and corresponding components?. And make sure the vertical have some resistance when test with ohmmeter.

Jestine

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

Dear Jestine

I am very have for your reply.

Now is very hard to get sometimes the replacement of a components.

If i want to get a reference book for electronics components in the internet what an i do please?

Waiting to here from you

Thanks Carlos

Hi Carlos,

Please visit this link:

http://www.donberg.ie/search?query=data+book

Jestine
http://www.JestineYong.com

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

Thank you for very informative pages. I am thankful for them. In the previous correspondence with you I asked you about the equivalent flyback manufacturers.

I eventually obtained a flyback from the original manufacturer!

However, although the flyback did solve part of the problem, I only managed to get a dark grey raster with a white bar in the middle of the screen.

I suspect that the horizontal yoke has gone. In a correspondence with another reader with a similar problem to mine, I would like to have asked the question – what are the typical resistances in a horizontal yoke.

I don’t have an LOPT tester, just a humble digital ohmmeter, and there were four wires – the smallest measurement was 0 ohms, and highest measurement was 1.6 ohms.

HI Anthony,

The resistance of the horizontal yoke is very small like 0.5 to 0.7 ohm and if you did not check properly you may thought it was 0 ohm. Since you are in this repair trade, if possible get a cheap flyback tester as it will make your job easier. Have a good day!

Jestine
http://www.JestineYong.com

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

Hi Anand,

Thanks for your updates and suggestions it really works .How do you get all this information .That day I learnt how to test resistors in ckt without removing them .You have suggested to use a ohm meter which supplies 0.2volts to the ckt ,thats great . I have a meter of MECO brand , it supplies 0.4volts ,its less than 0.6volts for silicon transistors but not good for germaniun transistor the other meter fluke supplies more than 2volts.where shall i find such meter please let me know .

You are welcome and as for the meter i guess you may need to check the spec of the meter from your local electronic supplier. Nowadays i hardly see anymore germanium diode. Do you still see those in electronic circuit? If not i guess the Meco METER will do a good job for you.

For repairing any monitor i have to connect it to my computer this keeps my cpu busy is there any way or an adapter that can give signals to the moniter under repair separately.Please let me know it will be a great help.

Yes you can try this VGA tester:

http://www.datasynceng.com/vgapdoc.htm

Jestine
http://www.JestineYong.com

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

Hi Jestine

My name is Marvin Magana ,first of all I hope you are ok ,I want to thank you for the books I bought does are great books.

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

.. may i ask if you have any idea on how to maximize the use of OSCILLOSCOPE?
i am looking forward for your reply.. thanks and regards..

Hi Nam,

Thanks for your email but i did not maximise using the scope as scope have lots of functions besides checking the waveform of certain testing points in circuit and semiconductor.

Jestine
http://www.JestineYong.com

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

Sir I would ask how can i know that the transistor are PNP or NPN.….Im newly gradute of electronics but my knowlegde is not enought and i want to learn more some advnce ticnics and i would like to thank you sir Bcoz to your site ^^ tnx sir yong…
Sir yong i hope can u help me? thank you sir yong ^^.

Hi Randy,

By looking at the part number and refer to datasheet and you will know if it is a NPN or PNP.

Jestine
http://www.JestineYong.com

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

Hi Waleed,

I have this problem with a tv set. it is a burnt resistor and can not find the actual value of it. it is in a vertical deflection section. 24 volts comes though the flyback to go through a 4.7 resister fuse then it goes to a diode then through jumpers it goes to a resister (burnt one) then goes directly to the third leg of the vertical ic. I could not find a schematic for this tv and still trying to find one but at the mean time is there way we can find the value of this resister? let me know.

I suppose it to be the VCC pin and this could be a low ohm resistor too. You may need to replace the vertical deflection ic as well. Use a 2.2 ohm resistor and see how it goes.

Jestine

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

hi mr yong.

what is difference between mkt capacitors and ceramic capacitors ?
which one of these are better?

(i have read in some of webs that mkt capacitors have less tolerance and good thermal coefficient and are suitable
for tune, oscilator circuits and any other circuit that deal with frequency. is this correct?)

thanks a lot.

HI Saeed,

Good question but i didn’t do any research about these caps. What i do was, if the cap have problem i will just replace back with he same type of cap to eliminate problem later. Well it could work better or give intermittent problem. If you have the time i suggest that you go ahead to test out these caps-it will be a good experience for you and me too (if you are willing to share). Have a good day!

Jestine

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

Hi Jestin,

How are you today. I am doing good. I have question about Zener diode testing from your ebook, Testing electronic components. I have doubt about a zener diode in my project. As I don’t know the voltage of it, I am a little bit confuse how to test it. In your ebook you said we have to know the voltage of Zener diode under test.

This one, when tested with analog meter setting in both X1 and X10K the pointer never move even when I changed the probes. Since I don’t know the voltage I cannot confirm it is bad. Before I removed it from the board the pointer did move. Could it still be a good one? Please let me know the better way to test.

Hi Rikhuma,

Fine thank you. A good zener diode should move when test out of circuit and if it did not move then the zener diode have problem. You must also place the probe hard enough on the leads to avoid soft contact problem where you would think it is a open circuit. What is the board location on the board. mark with “D”or “ZD”?

Jestine

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

Hi Martin,

Thank you for your kind assistance. About the previous TV I dicovered an open resistor on the supply line. I replaced the resistor and the TV came back to life.

You are welcome!

I have another CRT TV I am working on. When the TV is switched on, it would take about a minute for pictures to display, then after a few minutes the picutures get smaller. What might be the problem and how do I get around it. Thanks in advance.

First make sure the output voltages from the SMPS is good. Then check on the G1, G2 and heater circuit at CRT board and makse sure all is within spec. It could also be dry joints at the flyback area if the picture get smaller. Hope this helps!

Jestine
http://www.JestineYong.com

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

Hello mr, Jestine
the problem with the DVD it not reading media? not all cd ?

Located behind the lens a very small Variable Resistor -two- (DVD drive laser adjustment) How do I adjust these ? thank you and have a nice day refaat

HI Refaat,
Usually i do not turn the preset as it is already fixed by the manufacturer. If it can’t read the disc, you may have to check the spinner motor as a slow or a bad spinner motor could cause disc error. If the spinner motor tested good then suspect a bad laser assembly.

Jestine
http://www.JestineYong.com

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

HI Bailing,

Yes, the R,G,B signal from the LM1279N IC all are good measured at 1.2 V. I was using these three consecutive holiday to find where was wrong with the CRT board. I even couldn’t sleep well the first and the second day, and this third day is really a relief.

It seems that the culprit was caused by myself unconsciously. When I removed the shield of the CRT board, I broke a tiny path ( the blue cut-off preset ) close to one of the solder joint of the shield pin, see the attached photo.

I used up the first & second day to check nearly all the components especially the blue circuit but nothing was bad. So in the third day I used the voltage test to make a comparison list of test points, and I got a clue to narrow the problem.

These problem happen could only make you even better in electronic troubleshooting. This kind of problem can’t be learned from books and it will stick into your mind forever.

Now I have some questions to ask:
1. What are the function of the three R,G,B cut-off preset? How to make adjustment of those preset?

If the front panel color adjustment can’t make the screen better (you need a grey background raster) then you have to adjust it internally. Just turn the preset till you get a grey raster at the background.

2. About the yoke coil, I remember that you ever told me that if the yoke coil were bad, we must change the whole picture tube and the yoke coil as a unit. But, why I often see the yoke coil sold separately in my local stores?

Those yoke coils mainly are for black and white TV and monochrome.

Thank you my teacher, I always hope to be your good student.

You are welcome and congrat on your successful repair.

Happy vacation,

Same to you.

Jestine

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

sir,

compliments of he season. currenly am working on a dell monitor with cotinuous power blink, thanks to you actually i followed THE PROCEDURE IN YOUR BOOK ON how to repair monitor with power blink and fortunately enough it was the same model of dell that you used in he illustration in your book. i discovered that the actual culprit was the four transistors at the inverter section, replacing them brought the moniyr back to life but after sometme it started blinking again when i uncoverd the casing i realised that two transistos was blown and reading continuty, replacing it again the same thing happened i even checked the transformer but no result please what can i do

sam

HI Sam,
Check if the tuning capacitors are ok or not and usually located nearby high voltage transformer in inverter board. I came across low quality C5707 transistor and it blew again after few days. Replacement of the original transistors solved the problem. Make sure there is no dry joints in the inverter board too.

Jestine
http://www.JestineYong.com

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

Hello Justine,

The first thing I repaired after purchasing your E-book was a 20 amp 120v to 12 v power supply. When I first bought it it I used it 5 days a week and it worked for about 6 months. The problem was 2 shorted nte2308 transistors and a couple out of tolerance resistors leading to the transistor. In addition I also added a additional cooling fan to help keep the transistors cool. Everything else checked out good.

Another 6 months went buy and the transistors shorted out again. This time the resitors are ok. I also checked all the diodes and they also appear to be good working order.

Justine, any additional suggestions would be helpfull before I replace the NTE 2308 transistors.

Thanks

Vic

HI Vic,

If possible direct replace any cap that is corresponding in the circuit and make sure there is no dry joints too.

Jestine
http://www.JestineYong.com

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

HI Choudhury,

Respected Sir,

Its been a long time that i have not encountered any electronic problem.But this time i am having problem with an ATX board(CPU POWER SUPPLY).It was having low voltage output and finally causing no power problem.

I opened the cover and saw six leaky e-cap.

Now my problem is two of the e-cap are rated at 2200mF/6.3V,One 3300mF/16V,two 3300mF/10v and one 1000mF/10V.

I went to my electronic component supplier to find for replacement but i did not find the e-cap of the exact voltage rating.

MY DOUBT IS SHALL I REPLACE ALL SIX OF THE E-CAPS RATED AT 25V.

Yes you can but the size would not permit you to do do unless the power supply have some extra space. Generally the higher the voltage the bigger would be the size of the cap. I suggest that for the 6.3 volt you get a 10 volt cap and for the 16 volt you get a 25 volt cap for replacement.

Jestine
http://www.JestineYong.com

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

hi Justine,
thanks alot for your quick help,
here i have some very common problem with dell monitors.
the monitor powers up and you see the logo and the recangular red ,green,blue and black for five second on the screen and then the screen turns black.
do you have any suggestion.
thanks

HI Farhad,

It could be a bad backlight or inverter problem. Please make sure the supply voltage is still present at the VCC pin after the display goes off otherwise the mainboard is the fault. Check for bad e-caps at SMP, dry joints in the high voltage transformer pins and make sure also the tuning capacitors value does not run.

Jestine

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

Your Name: zindadil
Message: dear jestine yong, i have a crt mitsubishi 900u 19″ monitor, there was no power, i have changed powering transistor, and an fet a capactor 33uf 250v, now power is ok but pincusion is not controlable, pls help me to rectify it, here ia=s chasis of monitor is nfj 9905 pls reply my with tips to zindadil_aries@yahoo.com

i shall be so thankful to u if u obliged, thanks

Hi Zindadil,

I guess you may need to check on the B+ circuit and pincushion circuit as a non working B+ circuit could cause display to shrink at both side and you may think it is a pincushion problem. If you have confirm that the B+ circuit is good then check on the modulation diode nearby flyback for short circuit. Hope this helps!

Jestine
http://www.JestineYong.com

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

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11 Comments

jgmanza

September 29, 2009 at 1:06 am

Hello Jestine,

Well I bought the LCD Monitor book. I had asked about voltage testing before, and as you said, It is in this manual. Thank you for an easy to understand book. It is so much easier after I read a few times. I will keep you updated on my learning progress. Thanks.

Best regards and Thanks
Jorge

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soni

October 5, 2009 at 9:56 am

Good Morning
I have problem with my Television. The picture is bigger than actual screen.
I Had check board and I found resistor burning near Vertical IC. I had replaced it by new one and then burning again .
So please give me what is your opinion about this case

Best regards
Soni

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admin

October 5, 2009 at 8:04 pm

HI Sony,

If the resistor goes to the vertical IC then you must replace the verticaL IC too.

Jestine

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yong wb

October 6, 2009 at 9:42 pm

Sharp 21BTM
When I switch on , Standby supply indicator red is on and then turn to green shortly and then red again automatically .
Remote control then fail to operate it.

I need some general working principles on the IR unit over the supply and any specific area that i need to examine.

I have the circuit and only analogue VOM at hand.

Thank you.

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admin

October 7, 2009 at 7:42 pm

Hi Yong,

First you need to make sure the cpu is receiving good voltage. Then check that the crystal have sinewave. Is the output voltages from the Main SMPS good?

Jestine

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Anna

December 30, 2009 at 2:08 am

hi,

is there any replacement/equivalent of 2N5109 transistor?? please help me to find out.

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admin

December 30, 2009 at 2:26 am

Hi Anna,
From my databook the equivalent part number are:

BFS50, MRF515, MRF629 and 2N3948.

Jestine

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omar

December 9, 2010 at 7:01 am

hello Justin Yong,

i have a phillips lcd tv 42 inch
when i turn it on i have a bleu screen for 2 seceonds then it turns black but the sound still works.
it isnt the invertor,
can you help me please do you know what it can be

thank you

best regards

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admin

December 9, 2010 at 11:42 am

Hi Omar,

It can be one of the backlight have problem. Make sure there is supply voltage to the inverter ICS eventhough it already shutdown.

Jestine

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ronel

March 2, 2012 at 12:40 am

hi sir jestin

can you help me to troubleshoot?my monitor is turning green it could be lm1279n

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- Jestine Yong
  
  March 2, 2012 at 10:54 am
  
  HI Ronel,
  
  It can be the LM1279N or driver ic. Check also for the signal cable and make sure no broken wires.
  
  Jestine
  
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