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Electronic Repair Questions/Answers And Testimonials- Part 38

By on August 23, 2009

 

 

Hi Justin:

I really enjoy reading your book over weekend. your book is really straight to the point. I hope in the future if you will write more books on how to read schematic and troubshooting. Also how to use and set up equipment such as oscillocope.

I will follow your instruction and copy your book into my DVD.  Thank you for your advise. Have a wonderful day.

Thank You

Doan D

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

 

Hi,

 

I’ve got a video problem of Philips model 170B2M/40 C LCD screen.

When I connect a signal cable to a pc, it display a picture for 3sec then

switch the picture off – blank screen.

I have checked the power supply and tested okay.

What could be the problem.

 

Hi Simon,

Suspect a bad backlight and bad components in the inverter board.

Jestine

 

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

 

Hi

    I am a NEWBIE and I purchase the book from you and I found out that the electronic parts is not hard to study it. Since I was reading to book from your websites I could be able to test some of the parts I am familiar with. All though I dont have the right testers but I will provde those testers I will need in the future, I only have a small analog cheap tester but I learn something from your book. I already have an Idea what to do or to check about tv or monitor, It would be better if I could get any information about car stereo, because I have a few broken car stereo units in my basement that need to be fix. I hope you have an answer to my question. Thank you very much for sharing your knowledge Keep up the good work !!!  5 Star

 

R.A

 

 

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

 

Hello sir.Happy friend ship day.But delated.Sir i want some material to study about DIGITAL SIGNAL PROCESSING and DIGITAL COMMUNICATIONS.If u have any ebooks please mail them.

 

 

THANKS and REGARDS,

Vikram reddy.Tekkut   

 

Hi Vikram,

Sorry i do not have such information.

Jestine

 

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

 

Thank you for the riched informtions very informative with crstal clear for quick under standing.

 

Sincerely yours CHIEF FAGBOHUN O SALMUE CEO/MD FEFSON NIGERIA LTD.

 

 

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

 

Thanks again for the message I am glad that you  still continue sending newsletter about electronic repair and I hope this will continue even I did not purchase your ebook. To be honest with you your electronic repair tips help s me a lot.

 

Tito

 

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

 

sir,

     I  purchased ur e-book 6 months beore .I am very happy with it

 

Thank you

Jainat

India

 

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

 

 

thank`s for the article,how to check a tv damage by lightning.
i have a pensonic tv damage by lightning already check the board and only found the main fuse was blow after replace new fuse its blow again,can you give me a way how to fixed this problem

 

HI Zul,

Check other semiconductor especially the bridge rectifier and power IC.

Jestine

 

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

 

hi sir,

i have a problem regarding to sanyo tv korean no model number i think its 27 inches the problem is there is a horizontal retrace line at the top of the screen first retrace line is 5 white, then followed by 1 blue then 1 green then 1 red, what is the possible cause of this problem sir? can look at the vertical section or at the crt? thank your very much, hope you can help me.

more power and god bless…

 

Hi John,

Check the vertical section for dry joints and make sure the supply is good. If all tested good then direct replace the vertical IC and retest the set again.

Jestine
http://www.JestineYong.com

 

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

 

Mr. Jestine Yong,
I have to thank you for your time in sending all these information to me, I’m 59 years old and currently away from my country and just visiting my son. I come across your website out of curiosity because I used to have two flat LCD monitors before that I just junked away knowing it cannot be repaired, but interestingly, after I have read your report, I’m planning to give your website to a young friend who is into electronics when I get home. I’m sure it will help him a lot in his chosen field of work, but I want to read your report as well because now I’m beginning to read and begin to know something about electronics.
Thank you and GOD BLESS
Ray S

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

 

 

Hi Rexford,

And thank you for all the reports.

No Problem

.lest i forget, is there a way of testing a component without soldering it from the circuit board..

Some components can be tested on board like e-cap but usually i prefer to test components it off board which is more accurate.

Well is your place like a school that you teach people and at the end issue a certificate to them?

Is not a school, is a room in my office that converted into a technical room and yes i issue certificate of attendance

i am just curious..is it true that what you think you are is really what you are? if it is, then you are unique and intelligent cos you think so…God bless us all..


I can’t tell good about my self. Why not read from my blog at
http://www.JestineYong.com

Have a good day!

Jestine

 

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

Brother Great Job, keep it up can you show me on picture how to know the reading of yoke coil on CRT TV with normal meter.

 henry

 

HI Henry,

Only use Blue Ring Tester to test yoke coil as normal meter is not accurate.

Jestine

 

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

 

Hi Jestine,

I’m a bit intrigue with this LCD monitor brand, DELL E172Fpb and Dell
E173fpb. Symptom is Shutting down. When you check it, you can easily
pick up that the C5707 transistor are faulty. When you try changing
them, the monitor will work a couple of days and will shutdown again.
The caps are ok, the transformer as well. But what was causing it
shutdown after a day or two? Can we test the transformers on board or do
we really need to take them of to get a better reading. Amazingly, I
have 4 of this monitors and they are behaving the same.

Thank you and will wait for your advice.

Regards,
Arvin

 

HI Arvin,

Make sure the high voltage transformer does not have tiny dry joints and check that the tuning capacitor value is not out.

Jestine
http://www.JestineYong.com

 

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

Hi Tom,

 

I have read the report, and also purchased your e-book. Very nicely written and very informative.

Thanks for the support!

 

Recently I have been trying to troubleshoot a LCD monitor by Gateway HD2200. The monitor turns on, display shows, and then shuts down. I measured the voltages at the power supply, and the voltages were correct at no load. under load (light blub), the 10 volt line dips to 8.44 volts, where as the 12.48 volts test point center of one of the two Schottky diodes increase to 14.48. If I load the 12.48  volts, it dips to 10.48 and the 10 volt line increase to 12 volts. The Schottky diode on the 10 volts side gets hot to the toouch underload. I can not find any defective Electrolytics to look for possible leakage or shorts. All ESR’s checked out good. If I load the 5 volt line it dips to 4.75 volts. Would you have any suggestions…?? This power supply uses a dual controller FP6321A, 271I FET


Try check the backlight and the inverter board section. A dry joint in the high voltage transformer could cause such problem.The power supply seems to be ok. If possible compare the resistance of the top and bottom lamp circuit. Any differences in the resistance is a clue for you to trace from the particular point.

Jestine
http://www.JestineYong.com

 

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

 

hi mr yong.

i want to know smd component packages for example:how(what shape) is sot-89 or sot-23 and etc. beacase when
i want to identify smd component first of all  i should identify smd package and then search id code(marking code).
can you recommend me a website for smd component package style?

thanks a lot.

 

Hi Saeed,

Try this link;

http://www.ilriparatore.it/pagine/SMD/page0/smd0.htm

Jestine

 

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

 

Dear yong ,thank you

 

now i am busy in repairing the high voltage board of korian oscilloscope ,i test all the transistors with no failure in any , also i test the diodes and resistors ,my question is about the high voltage ceramic disk capacitors how can i test them , does the measuring of thier capacitance values decide whether if they need to be susitute.

 

 

best regards

 

Hi Mohammad,

Testing the cap value is not good enough as it can breakdown when under load. Since this type of cap is cheap and easy to get i suggest that you directly replace the cap and retest the equipment again.

Jestine
http://www.JestineYong.com

 

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

 

Hi Jestine,

  As for the Blue ESR meter, I use it almost daily.

 

Recently, because I need pointed tip to make measument on the boards, I decided to desolder out the original leads and fix one from test lead I bought from IC shops.  You know those that are meant to use with multimeter test leads.  There are good test leads on sale around that cost about RM7.50 or so.  I basically cut the test leads points and solder them to the ESR meter.  I hope the Blue ESR meter come with pointed leads to make measurement better or they are reason why it came with croco clips.

 

The Blue ESR goes haywire.. Measurement is erratic.  I decided to desolder back the original test leads.  Unit is Ok again.

 

I wonder why..   But I guess I got no time to waste to make the ESR meter haywire again since I want to use to check capacitors.

 

Anyone already knows about this?

 

Have a nice day, Justine.

 

HI Tan,

Try use a shorter test lead as a long lead could cause the reading to run. As for my Blue ESR meter, I’m using the Multimeter test lead too. I do not know why it come with croc clips perhaps it helps for beginners.

Jestine
http://www.JestineYong.com

 

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

 

Gud day Sir Jestine, I have a repair problem with Viewsonic CRT Monitor E50 (15″ monitor). I found the Boost MOSFET IRFS634a defective/ shorted all pin. I replace it with good one taken from another E50 Viewsonic. But the Boost Voltage is too high, around 250V DC and its very hot and the screen display is not full – its only about a quarter on the center of the CRT. I have to switch it off after switch on as it might burn the Boost mosfet again. Can you help me what suppose to be the problem? Thank you in advance and I’d like to tell you that I’m one of the happy people having learned a lot from your electronics skills since I found you in the internet more than a year ago. Eliezer

 

Hi Eliezer,
Check all the surrounding components in the boost circuit. If possible trace the gate signal as a bad gate signal could cause B+ voltage to shoot up. Check also for the safety cap value nearby flyback.

Jestine
http://www.JestineYong.com

 

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

 

Hi Jestine Yong,

 

I have justed visited and have signed up for your free report.

 

I need to buy a multimeter (analog or digital) voltage reader/device for my household.

Can you recommend a brand/series that is good and handy, yet not so bulky and not so expensive.

 

Thanks,

 

Razi  

 

Hi Razi,

Try Sunwa brand for analog meter and Pro’s kit for the digital meter.

Jestine

 

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

Hi Henry,

Thank you for your regular monthly repair newsletters.

I read them with interest and I also learn a lot from it.  I like your way of presenting the topic not only by text description but also supporting it with real photos and/or little diagrams. It helps to understand the issue and makes it easier to relate to actual “geography” on the PC board.

You are welcome!

 

I am new in this electronics (mostly TV) repair and I’ve got a lot to learn. I am keen to do it. Your Testing Electronic Components e-book, those newsletters and various information on your website are very helpful.

Thanks!

 

Now, I would also like to read many of the articles/previous publications listed on your Home page of www.electronicrepairguide.com . Many of them are marked as “for members only”. I thought that signing for subscription makes me a member but I still do not know how to access these articles. Please explain how to do it.

Sign up from this LINK and you will get all the previous, current and future repair newsletter.

Jestine
http://www.JestineYong.com

 

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

 

Hi Happy,

Hi Jestine,thank you for senting me this month`s news letter.

You are welcome!

Im having a problem with a Sony KV-XG29M20 model.the problem is its showing picture almost half way from centergoing downwards.The other top part opf the frame is totally down.what I did is:

checked my B+………..123V.(switching element is STRF6456).
frame B+………………… +13.40V
frame B-…………………. -14.76V
scan coil reading:
line……………………….. 1.8 ohms
frame…………………….. 8.8 ohms

When in operation it shows 5 flashes ,then the same time it will be of(50% on 50% off)
I replaced frame IC and it was blown in few mins.

What could be the problem ,Im now stuck.

If the IC blow there are few causes:

too high the power supply voltage to the IC

shorted corresponding components,

and bad vertical yoke coil

Jestine
http://www.JestineYong.com

 

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

 

Hi Chris,

Hi Jestine, I purchased your LCD repair course a while ago.

Thanks for the support!

I am having trouble locating places to buy IC’s such as PWM controllers and MSOFET chips for inverter repair. I live in the USA and parts suppliers like DigiKey don’t carry  and of these IC’s. I assume they are made by Chinese companies.

There is one company in USA that sell some of the LCD Parts but recently their service was not that good and you can click HERE to check out the blog post about this website. And my blog list of electronic suppliers at :

https://www.jestineyong.com/?cat=12


Where do you buy your IC’s from? Looking to buy small quantities.

From my local supplier but most of them do not sell LCD parts.

Chips like BIT3193, 0Z964, 4502, etc

Inverter IC generally very robust except those IC with the part number like 4411, 4410, 4502 an etc. Try email Luca at info@lavinci.it check to see if he have the parts that you are looking for.

Thanks

You are welcome!

Jestine
http://www.JestineYong.com

 

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

 

Dear Dave,
I have a 2N4416 TRANSISTOR (JFET-N-Channel UHF/VHF amplifier in a
TO-92 case). The problem is that it has 4 legs & I’m unable to find
out which leg is D (drain) S (source) & G (gate). Please help me out.

Prakul, India

 

Hi Prakul,

Try this link:

http://jp.ic-on-line.cn/iol_2N4416/PdfView/180499.htm

Jestine

 

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

 

HI Willem,

Hi Jestine, can you please tell me when using the light bulb trick where should the positive side go. Can you connect it to the collector of the HOT where you disconnected the collector leg. Negative I know should go to the emitter side (ground) of HOT. Can you please help me?

 

 

Please visit this link:

 

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

 

Then can you please help, I want to know on a TV that has the problem that it  does  not turn on. The volts reading of B+ is normal at HOT 110V. I changed the oscillator IC but still no luck. What is strange for me is that on the primary side at the regulator IC I get high volts my meter can read up to 1000V dc but it is not able to measure this reading. I get this high volt reading at both the primary and secondary side of the SMPS transformer but as I say at the Collector of HOT it gave me 110V and also at the primary of the flyback. This is a 51cm LG TV. Can you please give me some of your wisdom to sort this problem out.

 

When you say does not turn on is the power LED lit? Or it does lit but no high voltage?

 

Thank you for your interesting blog I learn more from you than any study material I studied thus far.

Thanks


You are welcome!

Jestine
http://www.JestineYong.com

 

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

 

Hello Mr.Yong!

Thank you for your e-mails!Your website is very interesting for me.

I’m interested in electronics but just a beginner which one of your books will you suggest me to buy  to start with?

Regards!

Rudolph

HI Rudolph,

You are welcome and i suggest that you start with Testing Electronic Components ebook first.

Jestine
http://www.JestineYong.com

 

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

 

Your Name: antonio samia
Message: Hi jestine I have problem regarding my ps2 model scph 18000.i want to convert it to 220,Any idea what part should i replace to make it to 220v thanks and more power Tony

 

HI Antonio,

Sorry no information about the conversion as different equipment have different circuit design. The fastest way is to use a step up transformer.

Jestine
http://www.JestineYong.com

 

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

 

hi sir

thank you very much sir, i check the vertical section w/ an analog meter  but the cap seems good, i dont have esr meter, im doubted of the caps so i clip a higher value caps in vertical section, first i clip the cap (470uf/50v) to this capacitor 100uf/35v in vertical section  then i was surprise the traces are gone and the height of the screen is adjusted /fit…thank you a lot sir and more power….

GOD BLESS YOU SIR AND YOUR FAMILY

 

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

 

Your Name: Amen
Message: I am a student, doing training at SABC, my supervisor gave me a task of fixing a television that was having a picture problem which ended up being a line and black. I first suspected the output transistor. when i tested it, it was faulty, I replaced it with another one and the TV switched on and off with the strange noise from the LOPT, now the LOPT is a suspect. my problem is that I have never tested a LOPT before, this one has got 10 pins and I have taken it out of the board. I only have a multimeter, can you please assist me on testing it while it is out of the board.

 

HI Amen,

Try this link:

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

Jestine
http://www.JestineYong.com

 

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

 

HI Nana,

i am Nana writing to you from Ghana.

Nice to know you.

i have read about noahtec and the marvelous training being offered there.i would extremely be happy if the ff doubts are cleared for me.what is the duration for the entire training?

It depends on which module you want to take.

are there schorlarship assistance for foreign students?

Sorry there is no scholarship available.

what about accomodation for foreign nationals,

We will find a cheap budget hotel for your stay.

how much does one pays for the entire course duration.

Is all listed in the noahtech website.

thanks for reading.i am the one who called you from ghana

Thanks for the call -appreciate it.

Jestine
http://www.JestineYong.com

 

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

 

Hi Boby,

1). TV- Philips 14″: suspected faulty CRT therefore is it possible to change it with other TV brands 14″ CRT with the existing or same main board?

If the crt have the same part number or sometimes quite similar part number yes you can replace it.

2). What is/are the equivalent transistors of 2SD4706 (chopper/power transistor)?

Sorry no information on this part number.

Jestine

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

Hi Jestine

I have a PVision LCD TV with model number PLD40T

This is the 4th one all off them with the same problem, they blow the caps in the power board C234(470micro F,25V) & C237(680micro F,10V)

As soon as I replace the caps then I got the picture back

I want to know what’s causing this

Thanking you

Bongani Ngubo

Hi Bongani,

It could the bad quality cap used. I ‘ve seen many in LCD Monitor.

Jestine
http://www.JestineYong.com

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

HI  Sam,

Wats the use of NTC in monitors??

To protect circuit from spike

How to check whether it is good or short??

It is like a low ohm resistor. Should show low ohm

Now i got a Samsung 55V monitor with No EHT problem..if u came through this
model,can u help me to sort out the problem easily??
power LED is glowing and all the output from SMPS sections are normal.RGB
cathode,heater voltages are normal….

Do i need to check any other area??

By following u r current newsletter(many thanks): In a DELL monitor i
found B+Fet short(B+ voltage totally drops).As per u r previous
newsletter,which component should i check next.?

You should make sure the flyback have B+ voltage in and the base of HOT must have a waveform. Please refer to this article:

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

jestine
http://www.JestineYong.com

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

Hi Ibrahim,

How are you?

I’m fine thank you.

tahnks for your fast replay, there is some thing i need to tell you about it, a 31DF4 in a secondary  part of power circuit, when I test it in theboard its appear shorted, when I remove it and make a test it is ok. the monitor get power back after removing this diode but no data, i put another one or any equivelant diode its too hot and test as shorted in board. Tell me what shall I do.

You should test diode off board and not on board.If it is shorted then use UF5408

What is you opnion to make a website for my self to shaer the experince of  fixing and repairing electrical instruments.?

It is good to have your own website. I suggest that you start a blog first like mine http://www.JestineYong.com
I will send the money in the begining of the september

Thanks for the support!

Jestine

 

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

 

Good pm sir. thanks for the advise to test the voltages of microcontroller and eeprom ic it has 4.98 volts and i solved the problem in the secondary side of smps. it has 2 ic protector which is n75 and n20. the N20 IS OPEN. wHEN you test it on board it looks it has a continuity or resistance but not up to full scale or to zero scale of analog. i compare it N75 and it deflect to zero scale. so i desoldered the N20 and when i test it continuity and it is open circuit. i replaced a new one and the display came  on. thank you also for monthly repair tips it’s a big help. God bless you more sir.

ZED

 

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

 

thanks a lot sir. i really apprecite it. i believe its one of the best book written on this subject.it really help me a lot than all ohther books on this subject. thanks you sir

 

Adil,

 

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

 

hi mr yong.

i have a crt tv which has a problem. when i turn it off a big white circle appear in center of display and gradually
minimize and then disappear. what is problem and which components are defective(spoilt)?

thanks a lot.

 

HI Saeed,

It could be a missing ground from the CRT tube to cold ground or the tube is already weak and need replacement.

Jestine

 

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

 

Hi  Waleed,

I have a mag lcd monitor. when you push the button, it tuns on for few second and the picture is very nice and very clear but it turn off right away but the power let stays blue…that is on. according to you lcd book, it is either a bad main board, cold joints or the converter ic or capacitors. well, I checked all the capacitors with ESR meter and they all checked fine. i stated testing voltages but first checking the main filter capacitors but when I turn it on, smoke came our of the back light connectors..I do not know why. I usually pay attention where to put the my meter probs so no mistake here. but smoke came out. any way, how to solve this problem. I left it in my shop till monday moring so I can come back to it with clear mind. please, I really need your help in this one. thanks and looking forward to hearing from you

First make sure the output from the SMPS is good then when the display shutdown make sure the supply voltage is present at the vcc pin of the inverter. If no supply voltage then suspect a bad main board. If there is supply then check on the inverter area and the backlight as if one back light fail the whole display would shutdown.

If possible compare the resistance between the top and the bottom lamp circuit. Any differences in resistance will give you a clue on where to trace the fault. As to why there is smoke i have no idea of it.

Jestine

 

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

 

 

Hi B,


It’s been a while since I last wrote to you. I have been busy with the twin and reading your Q&As. Hope you & family are fine. By the way, thanks for this month newsletter.

Yes, me and my family are fine-thanks and hope you have a great time with your twin.

Today customer brought his LG monitor, the problem is the display losing some colors, as you can see in the attached photo. The display is also dim, even turning the brightness to maximum and the brightness is not stable.

Taking some measurements, I got:

Heater 5.7 V
G1     -72.8V
G2     240-260V ( running away, not stable )
RK     21V
GK     24V
BK      31V
This is the first time I got this problem, and have been working for half day without result and would like to seek for your help.

What is causing the display losing some colors and how to repair it.

It could  be a bad tube, dry joints or missing red signal that had cause missing red colour. Try remove the G2 and retest the voltage again to see if it still 240-260volt or the voltage increase? Is the G2 voltage stable. As for the color problem you can test the RGB signal with your scope. It should have a similar waveform from the color IC and you need the datasheet to locate the RGB output pin.

Jestine

 

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

 

Hi Jim,

Thanks for u r reply sir..
As per u r previous reply,i replaced the power IC and found a bad
resistor(high ohms)..
Now it’s working fine..thanks

You are welcome!

How to check the base signal of HOT witout scope??

Just place the scope probe onto the base of HOT with power On.

Will problem in vertical IC(TDA4866) causes NO EHT??because when
voltage is applied to this ic,B+ voltage totally drops..

If the vertical IC shorted then yes it can cause other voltages to drop.

wats the normal G2 voltage in monitors??

About 250 to 300 Vdc and depends on what brand of meter you are using.

In which case we can directly replace FBT??

When the primary winding shorted, bulged or cracked

which meter is best for testing capacitor(pol/non-pol) &

ESR meter best for e-cap and digital capacitance meter for non polar cap

FBT windings??

Blue Ring Tester

which part of monitor will commonly go bad in the case of POWER LED
‘ON’ NO HIGH VOLTAGE??

Dry joints, open resistor, shorted internal flyback cap and many others

Jestine

 

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

 

just like I suspected, the back lights on the mag screen are bad. I found two good back lights not 19 inches but 17 and replaced them and it worked fine. the main problem is there is a dark side to the screen because the missing 2 inches because of short back lights. is there a way to compensate this. Thanks

 

HI Waleed,

Sorry at the moment no idea on how to solve the dark area.

Jestine

 

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

Hello Mr Jestine Yong,
Once again thank you for your news letter of August that I find really instructive. This helped me a lot to improve my method of fault-finding in electronics.
My prayer is that God grant you long life to continue to educate us.
To better understand the workings of a television, could you send me a detailed diagram of operation and an illustration of various stages of crt television.
Thank you in advance for what you will do for me.
Good day!

 

Hi Borohoul,

Thanks for the email but i do not have the full explanation of operation of TV. I guess you may need to invest a book on it. You can choose from variety of TV repair book from amazon.com

Jestine
http://www.JestineYong.com

 

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

 

HI B,

I had removed the sreen cable and tested the voltage again, and I got 332.5V quite stable. It is interesting to know that when I reconnect the screen cable to the CRT board, and retest the voltage ( still got the same running voltage from 240 to 260 V ), whenever I connect digital the meter probe to the G2 test point, the display always becomes dark. Is this phenomena also same with normal working monitor? Is this a proof that this monitor has problem with the picture tube ( weak )?

Now the screen display is able to be seen and the brightness is not stable, but with the screen pot turn to maximum. Are we allowed to turn it to maximum? Will this shorten the flyback life?

Is the meter internal resistance that had caused black out and it is normal for some Monitor. Try direct replace the G2 line capacitor and the value should be in 103 to 472 with 1 or 2 Kv. This capacitor breakdown that pull down the G2 voltage.

Also the heater is still too low ( 5.5V stable ) and I don’t see any component problem related with the 6.3V line. Why is the heater voltage lower than normal?

In some design the voltage is lower than others and is perfectly normal.

Talking about fusible resistor mentioned in your Q&A, are we allowed to change the fusible resistor with ordinary resistor?

Yes you can but some other tech suggest only the original. I replace it with normal resistor but the  value have to be same.

Could we know it is a fusible resistor by the marking on the board?

Some board printed as F while to some  was R. You can notice it by looking at the resistor as it is slighlty different from those carbon film resistor

Reading all your Q&A up to now, I am still not sure about where is exactly the B+ measurement shoulb be taken.

It depends on Monitor model generally from 60 to 80 VDC.

You mention that the B+ line should have about 110V,

This voltage is referred to TV

but why when we check with “Identifying Television SMPS problem” by using the bulb trick, we only got much lower about 50V in this B+ line?

The 50 vdc is for Monitor and is before the boost circuit. After the boost circuit it will end up 60 to 80 VDc.

Also I still cannot figure out about the function of the relay on the mainboard, what is it used for?

In power section-the relay is to use to activate the degauss and if it in the flyback area it is use to switch to other frequency by connecting it to the s-correction circuit.

There is always a 3.3uF 50V capacitor on the mainboard, is this a non-polar cap?

This is a non polar electrolytic cap.

Could we use a polar cap instead which is much smaller if it is bad, I cannot find that big small capacitance value here. Is the non-polar cap always bigger than a polar cap, assuming having the same capacitance value?

NO you can’t because it will blow but you can use a non polar like the metalized polyester cap.

I have now realised that even I could repair some bad monitors, but the knowledge I have gained is still too little, there is still many problems that I couldn’t repair, there is still a long way to go to really master the CRT repair alone!

For your info, even I had opened my repair shop, but I always close the gate door. I do this because firstly I don’t have much spare time to do the repair ( my wife would look me as if I neglect the family ) and secondly my main work is still teaching ( outside my house ), so our main earning still comes from teaching; and thirdly because I realise my knowledge is still too little causing me spending too much time to find the culprit of a problem though now I have already had most of the meters and tools.

Thank to our Almighty God, for you had led me to become a repairman. Hope that you could always guide me faster to master this knowledge.

It take times, patience and more practice and have a never give up attitude to succeed! Sometimes when you can’t repair a Monitor it will lead you to find a solution and this will make you more equipped in the future. Just imagine if all monitors comes in with only fuse problem and after few years your skill will be at the fuse replacement level only. Take the tough dog as a blessing as solving a tough dog problem will make you to become better in this repairing line. I wish i have a ready book on this subject (infact i have written a manuscript of a CRT Monitor repair-about 400 pages) but did not publish it. I wrote the manuscript way back in 2002!

Jestine

 

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

 

HI Rexford,

hi dear,hope you and your family had a nice weekend.

Thanks

i just want to know if FET are only in power supply line in a television or other gadget..

Yes in power supply and other gadget.

and what does a FET and a current sensing resistors do really…thank you.

Fet for switching the transformer and current sense resistor to sense any excessive current draw and feedback to the power IC.

Jestine

 

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


Hi Jestine;

I am very grate full that i have your book.
It help me very well.
I want to know what the tolorence of capacitor is.

greetings,
Girja

 

HI Anand,

Take 10% for all capacitors for easy reference.

Jestine

 

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

 

Hello my boss, I got WestPool Tv the model is WP-3401 S/S but after replacing the H.O.T transistor the screen comes on awhile but later it goes off and blow the H.O.T again, i have checked the capacitors,Diodes,Ressitors, but yet still it give me headache please i need your assistants.

 

Hi Abdoulie,

Check this Link out https://www.jestineyong.com/?p=403

Jestine

 

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

 

Hi Sir,

                  It is with grate pleasure that I am writing to you. I just want to let you know that you are the gate way to my success. All the news letters and the many web site that i see you, Just giving out knowledge to the world for free just makes me thank God for you. Well there is just nothing that i can pay back to you that would worth the kind of knowledge that you have giving to me, well i promise that i will sent something very special all the way from africa. Well, I wish you all the best May God bless you and your family. Please receive greetings from my family and friends.

 

Kenneth

 

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

 

Hi Toby,

Thanks for yet another informative article. I appreciate the time you take to write and illustrate each one.

You are welcome!

I have two experiences to share with you: A 21″ Sharp t.v came to the shop yesterday with high-voltage shutdown problems. I checked the components as suggested in last month’s article, but none of those were the problem. The culprit was the vertical I.C (TDA8403K). After changing that, the t.v worked fine.

The second problem was a similar high-voltage shutdown problem on a Sony 21″ t.v. This was solved by changing an I.C. on the crt neck board(TDA6108), which had three shorted pins, which were shorting a capacitor next to the flyback.

The smps sense that the vertical ic and the color IC shorted thus shutting down. Last month article was about high voltage shoot up more than 24 kv and shut down. So it is a different case.

I thought I’d share those with you as you have shared so much with me.

Thanks for sharing. Have a good day!

Jestine
http://www.JestineYong.com

 

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

 

HI Edwin,

SORRY TO BOTHER YOU BUT I WOULD LIKE TO KNOW IF YOU KNEW WHETHER DVD LENSES CAN BE ADJUSTED SINCE I DO SEE ADJUSTMENT PORTS ON THEM? IF SO HOW?

Normally i don’t adjust them because it is a factory setting.

I HAVE A SANSUI DVD PLAYER WHICH READ ‘NO DISK’ AFTER +_ 5-10 SECONDS.
I SUSPECTED THE LENS SO I REPLACED IT WITH A NEW ONE. NOW AS SOON AS I INSERT A DISK IT NOW READS ‘NO DISK’ ALMOST IMMEDIATELY.

I HAVE CHECKED ALL MY CONNECTIONS AS WELL AS THE RIBBON CABLE OVER AND OVER AGAIN.
PLEASE HELP IF YOU CAN.

Check the spinner motor as a slow spinner motor could cause the famous no disk  symptom.

Jestine
http://www.JestineYong.com

 

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

 

Goodday Mr.Jestine Yong
is it possible to test ic if yes then how can i test ic’s with about 14 led or leg

 

Hi Gideon,

You can test IC if you know the IC input and output pin otherwise it is difficult to test it. You have to refer to the IC datasheet for the pin information.

Jestine

 

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

 

 

Hi Jestine,

I did a little research and I come up with this .I asked an experience tech I did know this

things very well. Like you were saying Saturday .a varistor Is open sometimes and closed when the current is drawing is open depended on the circuit .Like in my job we have

some computer remote the varistor is like a fuse I put 70 vdc..I cannot blow it. like the thermistor you were saying it has a low resistance if it is placed on top heat sink the resistance should go up depended on it,s rating.The surge arrester I look at power board

on the device it is written Jensen 8266 .I did tell you it was 50″ sony.in the ballast there is the same device a litle small in size.it is written fb100.I did check both device with an

omhmeter the reading is infinity open .Next week I will order projection course. I will read

a few books and i will come up with an answer.Thank you.

 

HI Jerry,
Okay will wait for your answer. Generally when there is a surge or lightning strike the varistor will go short circuit and the thermister will go open circuit. However, in some circuit you could only find varistor and no thermister  and some circuit have thermister but no varistor (like CRT Monitor) and some circuit have both. Hope this helps!

Jestine
http://www.JestineYong.com

 

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

 


By the way, have you ever replaced a bad spark gap component in the CRT board? Could this component make trouble too?

So far i have never come across spark gap problem. Whenever it arc yo will know that either the pc tube or the flyback have problem (generating a too high voltage).

 

Jestine

 

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

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6 Comments

  1. Jie Wu

    August 26, 2009 at 11:09 pm

    Hi Jestine,

    Glad to find your blog. I am trying to replace my viewsonic(N2635W )LCD controller board ( part number: V260B1-C01 ). Problem is how I can disconnect cable from this controller. The cable is small white color and both side has same pin connector. Thanks

    Jie

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  2. admin

    August 31, 2009 at 9:24 pm

    Hi Jie,

    Sorry i have not come across this model before thus i could not picture how the connector look like. I guess you might need a gentle way to dismantle any clip (if have) at both side before pulling out the cable.

    Jestine

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  3. Ting Ban Kang

    September 6, 2009 at 7:06 pm

    Hi Justine,
    I am very new(beginer) and knows nothing about electronic, but I love medling with it. Using common sense and a bit of info here and there, at times I managed to repair small electrical items like table fan, hair drier etc..
    2. Recently I tried to repair my Toshiba CTV model 29AZ7E which only shows
    "white horizontal lines" in the middle. Can you give me some tips?

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  4. admin

    September 7, 2009 at 11:28 pm

    HI Ting,

    Check for dry joints at the vertical output ic section. Check also for the supply voltage to the vertical ic and if all tested good then direct replace the vertical output ic and retest it again. Make sure the crt yoke coil connector is connected properly.

    Jestine

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  5. Yosmer

    April 10, 2010 at 1:29 am

    Hi Jestine,

    I have one monitor dell E173FPb that I bought to repair, but did not bring the IC602 and not the value of that component, do you can tell me the value? I think it is an opto.

    excuse my bad English

    Grateful
    Tovar Yosmer

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  6. admin

    April 11, 2010 at 10:34 am

    HI Yosmer,

    Currently i do not have this model in my workshop thus i could not locate the value-sorry.

    Jestine

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