HI Soumitra,

Thank you very much for the big support to repair the LCD monitor. I am trying to send the amount through western union money transfer , my place is little far from the city so I am planing to go next Monday to the Indian State bank Guwahati Branch. I will pay 47 USD right .

Yes and thanks for the support.

Sir I have a problem in HITECH  Taiwan make Model – PWS 6600S-S , 6 inch touch screen monitor 24 volt operated ,
The problem is no back light , I check mosfet  19N20C and IC UC3843A may be  are ok, because in the IC UC3843 pin no 7 i am getting 8 volt and pin no 8 getting 5 volt DC,
Here I attach one photograph for your ready reference to understand the circuit & PCB.
Sir Please help me and guide me to solved the problem , in our unit two no monitor same problem.

No backlight means the inverter circuit or the mainboard is not functioning. Did the inverter ic have supply voltage? If the uc3843 is a smd ic then 8 volt should be fine but if it is a dual in line ic package then 8 volt is not enough. Try trace backward from the backlight connector and see along the track have any burnt/bad parts.



HI Karna,

Hello sir …..How are you ?????

I’m fine thank you.

I have a problem with my LCD monitor which is BENQ FP72E   . The problem is ,,none of it’s front buttons work…..Some six or seven months back after formatting my computer I was adjusting my screen bekoz the display wouldnt cover the whole screen……so black stripes on the sices horizontally ….if resolution was adjusted it would cover the whole screen I mean problem ok… but fat letters….so I was adjusting this and all of a sudden while adjusting the menu brightness button on the front of monitor I accidentally did off the displaly option I think… since then   front buttons show no response when pushed… I am sure that I switched the function off but I couldnt on it again …….With this the problem is I cant adjust brightness and I have eye pain because of brightness while at night….sitting in front of computer ……..May be there is factory mode or something like that ???? pls help me…

It can be factory setting mode or the inverter have problem. Before that try measure to see if there is dc voltage at the vcc pin of inverter ic. No voltage means either the start circuit or the protection fuse have problem.



Hello…jestine boleh berikan tips cara yang tepat untuk mengukur voltage dikaki ic no 7
pwm ic menggunakan digital multimeter.Bagaimanakah kedudukan probe meter?



Letak probe hitam kat kaki negative kapacitor yg terbesar di bahagian power primary side. Lepas itu, letak probe merah kat kaki pin 7 dan baca voltan dari meter kamu.



Hello Jestine,

I am a subcriber to one of your newsletters and wanted to ask you about dielectric absorbtion.  I have a switch mode power supply from a Hitachi PDP television that i am working on and after describing a auto shutoff symptom i was having a moderator of a forum i belong to said that my issue was most likey “a cap with bad DA or a reset circuit that is malfunctioning. It can create some unusual effects and is not uncommon, even in new caps. A DA of over 15% is considered bad, but I have tested caps at around 10% that would not work in some circuits. DA is also known as “battery effect” and will result in a cap voltage RISING after it is discharged.”

After some research into dielectric absorbtion i see that it can cause problems in certain applications but i wanted to ask you how often you have come across this problem in your years of experience.  I have seen the procedure needed to test the cap’s dielectric absorbtion (not as easy as using a capacitance or esr meter) and wanted to know if i was chasing a ghost.  The caps in my SMPS have very good capacitance and ESR ohms readings but even then could they have a high DA value and cause trouble?

Thank you in advance!

HI Tayo,

Actually to test a cap we need to test the capacitance value, ESR and the DA. But since there is no cheap or affordable meter that can test DA thus i do not have the real percentage of the capacitor failure due to bad DA. I have personally encountered few caps that tested good using the capacitance and esr meter and yet failed when under load. The only tester i known of that capable to perform the full test on capacitor is Sencore LC103 capacitor and inductor analyzer.



Thank you for your help on the power supply I have found the fault it was a Zener Diode but i can not fine a PDF of it shows as SMD but it not it part number Z18B with 2 leadscan you tell me is it 400mw 18v can I replace it other Zener

HI Warren,

The best is to use the exact voltage which is 18 volt. You can use a higher wattage zener diode.



Hie Jestine,

I hope you are doing alright. Thanks for all the support you are giving me. Everything is moving on smoothly.  Now, let me know from you, is it possible to get this book called ‘ Philips ECG Semiconductor Master Replacement Guide through you.  I am asking this because I find cannot access the sellers of this book.

So, please tell me so that I can plan in advance as I will be preparing to order the ebook called ‘ Repairing Switch Mode Power Supplies.

All the best


Hi Christopher,

The ECG is no longer in production and the company was taken over by http://www.nteinc.com . You can buy the NTE version from http://www.sayal.com. it is under the book category and look for the NTE 14th edition.



Thanx Mr Jestine for your guidance. Sorry took a bit long to inform
you about the good news.
The color TV was finally repaired.
Checked stability of all dc voltages and were good. Went further and
checked SDA and SCL. Found these blinking simultaneously with the
screen so I traced serial data and serial clock lines from the CPU and
led me to the TUNER, EEPROM and SOUND card. So I decided to replace
the 24C16WP with several new ones but this did not solve the problem.
Then I uprooted one from a junk card and this cleared the fault.
Why was this so?



HI Stanley,

Congratulation! The reason why a new one did not work is because it does not contain programs in or it has a different version of part number.




I have a problem with a circuit removed from a sewing machine foot control. The RIFA PME 2616MA510 (0.01mF) capacitor on the board seems to have blown but try as I may I cannot find the same replacement component anywhere online. My question is – what could I use as an equivalent?

Any help appreciated.



HI Jeff,

Try other type of non polar cap or you can try the same type of cap but with slightly higher capacitance value and voltage.



Hi Jestine,

Thank you for your kind help for helping me to diagnose the shut off crt TV. Anyway, I found the problem already cos my customer wants it urgently. The problem was at the 9VOLT ( 4 pin regulator ). The line connected to one of the regulator was really small and I resoldered it, so the set back to normal again.


Best regard



Hi there Justine,thank you for all your input on the SMPS,i appreciate it,well i
got a problem witch i cannot fix,maybe you can give me some help or input on how
i can fix it,it’s about,say 20 of samsung lcd monitors from 15′ to 24 ‘ i dont
seem to get the problem when i switch on the the power of the lcd’s the monitor
switch on for about 2 to 3 seconds and just switch off,i can still see the
picture when i put a bright light againts the screen,it’s like the backlight
just switched off,thern when i switch of the screen and switch it on again it
does the same shows for 2 to 3 seconds and switch off again but the background
is still on just the backlights is off,theres nothing wrong with the tubes i’ve
checked them,CAPS is working fine aswell,all my voltages from the inverter to
the mainboard is there,what can i do please HELP ME, I’m BEGGING thank you in

HI Colin,

First you need to make sure the output voltages are good and stable. Next, make sure no bulged e-cap and no dry joints in the high voltage transformer. If all check to be good then one of the backlight have problem.



greetings my friend. it has been a while since I sent you a question. any way, here is my quesiton.

I am working on Philips LCD monitor and most of the time it is working fine. but sometimes the disply start going on and off and so is the stand by power led. it goes from green to nothing and green and nothing..it does not go to orange stand by..just from green to nothing..off. any ideas.

someitmes I turn it on the whole day and nothings happens..that is strange. I resoldered every joint in the power suppl and the hight tension area..but not that big of a difference. any ideas? let me know. thanks and God bless

HI Waleed,

If the MCU is receiving good and stable voltages then the problem is in the MCU. Try reflow the MCU and if the problem still the same then suspect a corrupted program in the MCU.



Hi JY, please how do I repair my Laptop screen. It has an opaque 2 cm wide vertical strip in the middle of the screen. It is an LG X120. Trouble shooting reports that display is working well!


Hi Wanangwe,

This problem usually cause by bad LCD panel and you need to replace it.



Hi Jestine,

Good day!

The moment I successfully downloaded your eBook SMPS Repair Guide,

I just can’t stop reading it. I’m so lucky that I have stumbled upon your website.

Your ebook is amazing and a real blessing because I have been looking for this kind of book for ages.

Now I am hooked and want to keep going that I need all the rest of your e-books to attain the best

knowledge about electronic repairs available from you.

Thanks for everything.

Have a great weekend!



Hi Justine,


After re-solder Ziner, transistor, fet backlight connector, problem become solve, thanks for help.

How about dc voltage not stabel – for example 15v ok but 5 v dc meter shows up and down.

Is it becouse of feedback also


HI Hasnol,

This mean there was dry joints in the board-congratulation!. DC voltage not stable can be due to the 5 volt line load problem or bad components in the 5 volt line like bad e-caps and etc. Try replace the load with a light bulb and retest. If it is stable then the problem is in the load.



hi Jestine

what kind of device to check southbrige/northbrige chip in the laptop mainboard?

Hi juan,

You can use your finger to touch it. if it is very hot then it has problem. Or you can use a laptop post card to identify the fault.



Is it possible to repair a laptop motherboard when the charging circuit has failed?
I have a latitude e6400 the power adapter test OK and the DC Jack test OK, but the battery does not charge.
Have tested with new battery.
Have tested with new power adapter.
any ideas?



Hi Tony,

Most probably the components fault in the charging circuit. It can be due to bad voltage regulator ic or those charging circuit Maxim IC.



hi sir jestine,

how do you open a adapter of laptop,, if i use screw driver the edges will not nice to see…

do you have some techniques so that the addapter casing will notdestroy.



HI Lito,

Try this link link:






HI Muhammad,

If a semiconductor burnt in the power supply, one has to check all the components in the section which include the primary winding of the power transformer. It could have other components shorted.


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