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Electronics Repair Questions/Answers and Testimonials -Part 72

By Jestine Yong on January 31, 2011

Thank you very much Jestine.

This link worked perfectly. I have started my reading. This is the first time that I am actually enjoying reading SMPS. Before this I got totally frustrated in trying to understand the material.

Thank you once again for this explicit SMPS tutorial.

Best Regards

C Riley

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

Hi Jestine,

This E-book (Power supply repair) is amazing and is worth the money, You have worked

hard on this book, and i give you top marks,i have been into electronics all

my life , and this book is truely amazing. well done.

Kind regards Bill Franklin.

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

Hi Jestine,

Happy New Year! I’m sorry for so long reply. I know the fault already why both sides of monitor has been curve. I check the modulation diode and i found out that has problem. So i replaced it immediately and i surprised. The monitor got back its original shape. We didn’t notice that the modulation diode has 3 pins. We think that it is a 2 pin or a regular type of diode which has an anode and cathode. By the way thanks for the advise. Thank you and more power.

Jewyn

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

HI Patrick,

thanks for the new year welcome. Thanks also for the repair newsletter.Hope every thing is well with you and yours.

I’m fine thank you.

I have a question : I am working on a 14 inch toshiba crt colour tv,the problem i have it shuts down after 3 seconds after powering up.
I check the voltage on the main filter cap it was about 156 volts DC witch is about correct but checking on the secondary side of the switch mode transformer cap it rreads 196v thats not correct right? its suppose to be about 133v could you guide me to where my problem might be.

If this tv is using optoisolator IC then you may check on the components in this area. A resistor that turned into high ohm could cause the B+ voltage to shoot up.

Jestine

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

Dear Jestine,

Thank you very much for your heart felt Best Wishes for 2011 . . . I would
like to thank you very much from the bottom of my heart for the valuable
hands on repair information that a text book cannot provide . . . what you
have sent me over the time I have known you, is a Life Time of Years of
experience over a lot of Years . . .

Jestine, may I take this opportunity to wish You and Your Family A Very
Bright, Lots of health and Global Peace to Everyone for 2011 ! Thank you
very much for your valuable time and hard earned work it will always be
remembered and used . . .

Take care and God Bless You and Your Family.

Yours sincerely,

Albert

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

Dear sir

I have purchased ic smd 74hc4053t instead of hef4053bt.

can i use this? pls tell me

thanks and regards

Fahimuddin

HI Fahim,

You have to try it. Some board could work on different version and to some it will not work and give intermittent problem.

Jestine

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

hi Jestine, what causes flyback lines?

Hi Obisa,

Weak tube, defective g1 circuit and bad vertical ic.

Jestine

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

Hi Jestine,

That was a fine article.

I think I now has buyed and downloaded all your books and reports.

I like them, easy to read and understand. All pictures do it more easy to
follow your instructions.

Thank you for help.

Best Regards /Mikael H.

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

respected sir
i am very very very thankful to you.Sir your articles are very useful
and easy to unstand.Sir i read many electronic articles but i don’t
understand but after reading your articles my confidence level is
increased so i am very glaid and my best wishes for you, may your
articles becomes very famous around the world and help others.

Rakesh from India

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

Hi,

I’ve got a problem in calculating a resistor value that has the

following colour codes:

red,red,silver,gold,green

Will you please assist me.

Regards

Molefi F

HI Simon,

Ignore the green and it should have 0.22 ohm.

Jestine

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

HI Dian,

Hope you are well and that you enjoyed your hollidays with your family.

My family and i are fine-thank you.

I wanna thankyou for your hard work keeping us inform all the time that really ease our problems fixing electronic equipment.

No problem.

I have an interesting story. I am currently trying to fix a switch mode powersupply that is used in an IGT video slot machine.

It came in to our workshop for repair. I took out the powersupplly and start doing fault finding. The fuse was burnt and start testing the bridge, resistors ect. I came to a Power Mosfet. No. 20N60SB. The Mosfet was shorted. I start testing all the other components and didn’t find any faulty one that could cause the Mosfet to have shorted. I did not have the exact mosfet so i use another n-channel mosfet.

I replace the fuse with the 250V lamp and switch it on. Well the Mosfet imediatly got very hot and shorted again. So some where must be a faulty component. Have not found it yet.

So I took out the Mosfet and start it up again without any mosfet on. Well geuss what. The outputs is working. I can put on load and the 24V,12V and 5V is working fine.How can this be possible without that Mosfet? What is the purpose of this Mosfet then?

I have attach photos of this Powersupply without this Mosfet so that you could maybee get an Idea. I have order new Mosfets of the same description and value.

I thought I want to share this with you.

The Mosfet most probably is part of the power factor control circuit thus without it the power factor circuit would not function but the main power supply is till working. You may google more about power factor correction circuit. The power supply is till working because it has another Mosfet in the primary side.

Jestine

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

HI Ver,

Hi Jestine its quite long time now its new year again that i have not hear or communicate with you except your monthly letter you send to us member.Well, I hope you’re Ok and your family’s health.

My family and I are fine thank you.

Actually i just want to ask your help about my LCD monitor problem i have Dell E177fpc the problem is at first it just shot off power indicate green is on i check all capacitor capacitance and esr all ok.And now the power is like it is oscillating as i can see on indicating lights and monitor of my meter, and it can not switch off the signal is always there 4.2 volts but the switch transistor it does not activated, i suspect the main board is giving the problem because i can not switch off the signal although power can not reach to transformer, back light are ok i remove and test outside.I think this can not be repair except to change the whole main board or i will just salvage the parts for future used.

I would appreciate to hear your suggestion,

If you found that the supply voltages to the mainboard and the power led is blinking then yes the mainboard have problem.

Jestine

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

HI Ng,

After reading on your free articleon the LCD monitor, I tried my ERS
meter and tested 2 non-polarity cap, both read exactly 2350nF on my
Fluke 289meter but very surprised it was not detected by the Blue ERS meter.

It is good to have the ESR meter.

I had other capacitors tested ok on the Blue ERS meter, such as 2200uF
35V with ERS 0.11value or 160V 100uF shown ERS value 0.23. So I think
the meter are OK.

Yes the meter is good.

I also tested one 16V 1000uFwith ERS 0.32with Fluke read 970uF, is this
ESR value acceptable?

I guess it is not acceptable. Just direct replace otherwise the cap may breakdown after few months down the road.

I suggest that you refer to this link also:

https://www.jestineyong.com/?p=1314

Jestine

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

Jestine, Please give me a step by step way that you could make me a great LCD, PLASMA, LED television repairer, step by step books to download or hardcopy books are the ones that I like best, so if you would please give me in order what you would do to become a great television repairer, books to get tools to buy or any other things that will help me accomplish this in a short amount of time, PLEASE HELP ME DO THIS IN THE SHORTEST AMOUNT OF TIME, say six months or less, THANK YOU, MARTIN P.

HI Marty,

I suggest that you make yourself pro in testing electronic components first. Next, set your target on what you want to repair. Tv or monitor or audio equipment and etc? Then get a book opn that subject and join membeship website or even forum. Focus it and you will see result very fast. If you repair all kind of electronic equipment, you will confuse and at the end you do not know much about solving a particular equipment. Be prepared to invest on test equipment too to speed up your repair work.

Jestine

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

HI Romulo,

sir its been a year since i sent a letter to you for now all the repair tips you’ve given to me are all a great help and for that i thank you a lot

You are welcome!

but i have this question thats bothering in my mind and gives me a headache hope you can help me again this time i’ve got a lot of dvd repairs that can read cd,vcd,mp3 but not a dvd dics how is that possible i only conclude that the decoder module is faulty so what i do is to replace the whole decoder module so here is my question sir whats really the cause of this problem is there a bad component that cause this better than replacing the whole. Thanks

I suggest that you check the spindle motor. A slower spindle motor could cause such problem.

Jestine

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

Q- what ia the meaning of this shortcut words (EMI,RFI,ESR,CRT,OCP) that mentioned in ebook?

HI Hashem,

ESR is equivalent series resistor
CRT is cathode ray tube
OCP is over current protection

EMI is electromagnetic interference

RFI is radio frequency interference

Jestine

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

HI Rene,

It’s been a long time since my last email. I hope everything’s fine with you.

I’m fine thank you.

Anyway, I’m troubleshooting an atx power supply of a computer. It looks fine and it seems working. I tested it while it’s still attached to the cpu. The bios displays the information on the screen. So that made me think that it’s okay. The problem starts when it tries to detect the hard disk and the cd-rom. The hard disk will make a noise indicating that it’s working BUT I noticed that it is spinning very slow. The cd-rom won’t power up, no indication that it turned on. Even if you press on the eject button nothing happens. I suspect that the supply is very low. I took the power supply out, checked it, and it looks fine. Nothing burned or broken. I measured the output in every jack and they all have the required voltage, 12, 5, 3.3 and the rest.

I have a working atx power supply and connected the cd-rom. It powered up and you can eject the tray. I have both the power supply on the bench and used the same cd-rom. Both are working and they have the same supply. The only difference is the power supply that I’m working on can’t make the cd-rom work. It’s weird. Any suggestions?

By the way, when I measured the voltage output from the jacks I noticed that the meter won’t stay put. It will show the required voltage like when you are measuring 12 volts. It registers but the hand wiggles a little bit. Unlike with my power supply the hand stays put.

This problem is puzzling. I’m still working on it trying to find the defective part. I hope you can give me some suggestions what makes the hand on the multimeter wiggle and why it’s giving out the required voltages but can’t provide enough power to turn on any 12 volt device on a computer.

That’s a bit wierd to me too. Usually if all the output voltages are good, it suppose to work well. I suggest that you directly replace the filter cap in the secondary side and retest. Before that, place your analog scope to all the output voltages (testing the line one by one) and power it on and see if there is any slight drop or not. Digital meter may not fast enough to capture the slight drop in voltage.

Jestine

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

HI Walter,

I want to find out if u know about a Smart Tweezer , that measures

diodes , caps, ciols and resistors

Yes i do have one

I want to know if it is very accurate and what brand do I have to buy

and will u be able to supply me one.

I bought it from http://www.advancedevices.com and i do not sell this meter

I also need something that measures Transistors that gives me the values and if PNP or NPN and gain ect

Try the tester from peakelec.co.uk

I need to get myself tools to make my work easeir , because everything

on the vehicles become electronics and I am battling

all the boards is surfacemount components

If u have any other sugestion for tools to measre all off this comp it will be good

You can try huntron.com
but it is very expensive

I have a board now that poped a comp it looks to me like a transister , but it burned badly so I cant see any numbers on it .

There is three off that comp next to one another , but I am afreight to replace it with the same as the other two and mayby burn something else.

Is there a way to determine what sise transister to use.

I have attaced a photo The number on it is P0242

It should be the same number and you need to take the risk since there are no information about it

Jestine

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

hi justin
I have a problem with UPS RS APC 1000, where often there is alarm overload, but no load is attached to the output of the UPS.

what is the problem, is there any mosfet must replace damaged or problematic batteries.

maybe there is your experience with cases like this?

Thank you
Robert.

Hi Robert,

Since i did not venture fully into UPS repair thus i can’t give any advice on this. However, i knew that for APC UPS, the eeprom data corrupted could such problem. You may need to replace the eeprom and retest.

Jestine

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

greetings my friend, i hope this message finds you well and in the center of God’s will and blessings.,
I need your opinion on this lcd that I am working on.
it is philips 170C.
sometimes, I runs for a week or more without shutting down but sometimes it runs for five minutes then it shuts down. I checked all the capactors in the power section, primary and secondary and they all checked well. I thinking about loose connection somewhere in the power section or the high voltage section..any advice will be highly appreciated
Waleed

HI Waleed,

If the led is off, is there output voltages from the smps? If yes then the MCU in the mainboard have problem because the led signal is coming from the MCU. If there is no output voltages then suspect bad components in the power side. Most probably component breakdown when under load. That means you have to direct replace the component (try semiconductor first) and retest.

Jestine

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

HI Jannie,

What is the right way to test LM317T Regulators?

Power the board and test the input and output voltage. You need to check out the datasheet of the ic.

Why is it that when I test relay coils with blue ring tester that only one yellow led comes on or just the two red leds?

Relay coil can’t be check with blue ring tester because the inductance is not high enough to register a reading in the meter. A resistance check (ohms reading) is already good in checking the coil of the relay.

Must you test them on board or off board?

Test it off board with supply voltage apply to the coil and you could hear a clicking sound.

Jestine

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8 Comments

Amir Mukhtar

February 2, 2011 at 4:34 pm

Sir Jestine
i have a question about LCD interface connector. does it possible DFP / DVI-D connect to SVGA 15 pin D type connector . means Can i watch screen from VGA card connector to DFP / DVI type LCD monitor.
please help me out. plz provide us to VGA to DVI / DFP convertor diagram.

Amir

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admin

February 3, 2011 at 9:48 pm

HI Amir,

I have not try that before thus i can't provide an exact answer to you. I suggest that you do the R and D and see the result. You may access these link to check out the pin specification:

http://en.wikipedia.org/wiki/Digital_Visual_Interface

and

http://en.wikipedia.org/wiki/VGA_connector

Jestine

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Osman ALSinnary

February 4, 2011 at 2:41 pm

Dear Jestene
Happy newchinese year****
****
I have an LG 710e Monitor , and have the same problem with the MOSFET transistor Q719 [ It has been burned(shorted) three times] and ireplaced it.
Also i found the resistor R809 Open and replaced it .
After replacing Q719 & R809 the Monitor worked for 1 week then the same problem again .
That make me confused .
Thank you in advance for your kind respoce & reply .

Cheers
osman

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admin

February 5, 2011 at 5:25 am

HI Osman,

Where is this fet located? the power side or the B+ fet? What was the actual complaint?

Jestine

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Osman ALSinnary

February 5, 2011 at 2:10 pm

Thanks 4 ur kind response

B+ FET Q719

Thanks again

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admin

February 5, 2011 at 11:29 pm

HI Osman,

I suggest that you check the B+ coil and also if the flyback have any problem in the internal capacitor. Please refer to the link below:

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

Jestine

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anor, arnel normandy

February 9, 2011 at 4:57 am

pls. help i have a goldstar 14inc. tv dead, the flyback is brocken but the problem is the # of flyback was erased and i cant buy for replacement. any one can help?

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admin

February 9, 2011 at 5:29 am

HI Anor,

Try email the owner of this website:

http://www.hrdiemen.es

Jestine

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