Electronic Repair Questions/Answers and Testimonials- Part 30
Nice to meet you!
I used to read your LCD-monitor-repair book, i’m suprised that book which you write is excellent. It ‘s easy for me to understand how to find out faults to repair when i read that book. So i ‘d like to improve knowledge of repair.
Thank you so much!
I have bought your book “testing electronic Component” and found it very useful.
Hi Jestine Yong,
Good night, Thank you… Thank you so much for your help and knowledge.
I DID IT, I replaced two electrolytic capacitor, switched it on and the screen works. Wow, Its my first time to solve this problem and I cant sleep, I’m HAPPY. Thanks to OUR Heavenly GOD for providing such a wonderful person like YOU – Jestine.
I am enjoying the e-book and learning lots. thanks for the reply.
I love your site.It has the most info on it that I have seen yet.
Sir gud day..what is the problem of the monitor the display or brightnes is
like a disco lihgt?the brightnes is high and low..what is the problem?
Check and make sure all the secondary output voltages are constant.
Thanks alot for this Feb. newsletter its very usefull for a junior tech like me and to others. God bless
I have enjoyed reading your different reports on repairing LCD monitors. I have been successful with fixing a few of them.
I think you are really a great man with open heart to give good suggestions and guidance to persons coming to this field to solve their problems and enhance skill.
thanks for your report its been very helpful. I followed the the out line on how the power supply works and I was able to repair my old power supply for my old computer.
once again thanks
you are a great man, at least I think so because I have truly resolved my Benq monitor life. I will build a esr meter for myself according to your recommendation. Thank you !
Hi Jestine Yong,
Good morning to you and your family.
Yes, answer to your question, I really love and desire ELECTRONICS. I just learned basic electronics from your reports and within that 5 days of reading, now I can solder and desolder components, Test resistors (color codes), Diodes, capacitors,still learning on the function of the circuit boards etc.and still desire more to know on electronics.
You are so kind and generous with your knowledge and help and GOD WILL RICHLY BLESS YOU AND YOUR FAMILY.
If all the output voltages are tested okay then suspect a bad lcd panel. Bad Lcd panel contributed about 90% of white screen problem.
Thank u Mr. Young for the help, it was most helpfull. It took me about one month to partly fix a blown audio amplifier. A (Boss C1000) 4 channel 2000 watts. Some how the mosfet power supply transistors blew, and when replaced kept blowing again. the info from u narrowed the problem to the PWM circuit,i borrowed 2 transistors from another part of the amplifier sacfiricing two audio output channels so the pwm cit could work . I need this transistor [ A1023 ] or a substitute do you have any info.I tried serching the net and ECG book, found nothing. Can u help me? thanks in advance.
From my databook the sub for A1023 are BC556, A970, A1049 and A1285.
Hope this helps!
i have Likom LCD monitor 17′. The problem is hen Turn On the color is black and white. do u know what the problem for this LCD?
Try on another cpu. Check also the menu setting of the monitor.
Dear Mr. Jestine,
HP 1702, 17" LCD monitor (not old) display is dim with reddish picture.
Hi Abdul, Dim display and reddish is Backlight problem. Guess you have to remove the backlight and replace with a new one. Please take extra precaution when removing the back light.
I bought your LCD monitor E-book and still read it….it’s very good book…
Where can I have some test equipment taht you mentioned? Since it's rather difficult
for me to find it...o yeah..i live in
for you to know... Indonesia
Hi R, Glad that you like my ebook. May i know which equipment you are referring to? Currently i'm only selling two types of test equipment: http://www.electronicrepairguide.com/blue-ring-tester.html and http://www.electronicrepairguide.com/blue-esr-meter.html Thanks! Jestine http://www.JestineYong.com
Good Day Justine,
I have an elecricial engineering technology background and currently employed in that field of work. I have only being working in this field a couple of years and am looking for reference material for troulbeshooting electronic components as my strength is in industrial electricial systems and I work like to learn how to troubleshoot printed circuit boards and associated components. Will you book be of use to me?
Thanks for your email and i guess my ebook will suit you because it teaches you how to accurately test electronic components. Once you are good in testing electronic components in fact you can start to troubleshoot any electronic equipment plus it comes with my support too just in case if you have problem dealing with the repair. Hope this helps!
Greetings my friend, hope this message finds you well. I am looking for an eprom programer and copier. what is the best to buy and is it possible to build it myself..do you have an schematics for it..please let me know. i have been trying to get it off the net but I got a lot of them and do not know which one I need..please advice. Thanks
Sorry no schematic on this project.
Thanks for your valuable information.
If I am not disturbing you, I would like to ask for your help in my venture.
I live in a Village in South part of
Please help me.
Thanks and Regards
Thanks for your email and congrat on your plan. However since i have already left the designing work more than 10 years ago and concentrate in electronic repair, i guess i could not give you any advice in this topic-sorry!
How do i get your E-book?
Yes you can buy directly from the website. Its an ebook and after the payment you will get the download link.
I have a question.
I have a NEC pcengine Duo
What all do I need to test it and how does one clean pcb?
You test it with multimeters to check on the resistance, voltage, continuity and etc. Clean pcb with Thinner solution.
I was told I need a ESR tester which I don’t have.
Yes every electronic repairer must have esr meter in order to speed up their repair work.
Hi, Jestine Yong,
I’m having problem with my 19’inch LCD Monitor. When I switched it on nothing display, only the green light always blink. Please can you help me solve this problem or of it possible you send me a simple diagram on how to troubleshoot this problem.
Thank you and hope to hear back from you.
Green lights blink with stable output voltage suspect a bad mainboard. Green light blinks with fluctuate secondary output voltage suspect bad filter caps and also some other components in the secondary side. Hope this helps!
Dear Mr. Jestine
Fisrtly , I say thank you for your best advise.
What a different data specification betwen FOR1D with FOR1B or FOR1G?
Because I need FOR1D but stock not ready, so any other SCR same spec for “FOR1D”?
1. What kind of your books can show general knowledge to diagnosis Arcade Chassis problem without chassis scheme?
The best you get homer l davidson book on “troubleshooting and repairing solid state TVs” as many of tv circuits have similarities with the arcade chassis.
2. what kind of problem cause
If the heater voltage is derived from the flyback then missing a B+ voltage and h.driver signal would not energize flyback thus no heater voltage will be produced. No heater voltage means no glowing light in the tube.
3. What is the most general problems cause power supply voltage getting lower than before? Is it related with capacitor or from transformer?
Most e-caps, dry joints and high resistance in resistor.
Thank you for your response to my mail, i am impressed and appreciate the effort.
With regards to the i c str6656, having 5 pins i dont know how to test it .
I dont see it in your ebook ( electronic repair guide ) Please assist.
Find the ic data spec and see which pin is supply pin (vcc). Once you found the pin then power on and use your meter to check the pin and make sure have voltage there. Then use a scope to check for the output waveform.
Thanks for your valuable advice Repairing notebook is only desoldering IC chip using the infrared welder ( that hot air desoldering station cant do ) the price with Monitor and soldering gun is around thousand RM what the repairer told me is just of telling that the instrument is expensive so he have to charge expensive. From what I think problem with power in notebook does not need the infrared welder just the hot air gun station set will fix it is that correct?
Yes, with the rework station is already adequate unless you have some extra budget to invest in those expensive equipment.
By the way I got the circuit of Dick Smith LOPT tester Is the Circuit reliable?
Yes that’s the first generation lopt circuit and i have members that had successfully built it.
because I like to build one with my electronic friend who is good in DIY electonics Projects. Bye God Bless and send my regards to William too hopefully to come to KL to see U both bye.
Okay no problem i will send the regards to him.
I downloaded your report already it’s very usefull report.I’m computer technician here in Thailand i realy like your book and i still learn more to improove my skill for LCD monitor and hope to success soon.By the way thank for your good instruction.
Another interesting point is when I want to measure the G2 voltage, I find there are two points marked as G2 on the CRT board, where they have resistance 215 Kohms between them; which one should I measure the screen voltage. See the attached photo. Is the screen cable from the FBT not the same with Grid2 of the CRT?
You can measure both points. If there is problem with the G2 both the G2 points will drop at the same time.
One of my favorite website is HR Diemen because in the past I could see the flyback pinout of any FBT in this link http://www.hrdiemen.es/data/esquemas/ ; unfortunately now I got forbidden message. Do you know where & how to see the flyback pinout of any FBT? Do I have to buy their CD?
From the indonesian blog i have posted few days ago. click on the view link in his blog and you can view the layout diagram of the flyback but not all flyback. guess you have to buy the cd if you want a more indepth of internal flybaxck transformer.
I don’t know why on the second day of burn in test, the monitor display is becoming unstable again, often disappear for a second and then comes back again, and sometimes I could also see a disturbance horizontal line coming up.
I just feel I still lacks the knowledge of the functional block & the use of each component on the board, makes me always doing the blindly guessing work about which component is failed.
Tonight when the surrounding environment is quiet, I’ll send you the AV file describing the condition of the monitor while power is on, for you to have a real feel of it.
Wishing you all the best,
Okay no problem but when the monitor turned unstable you must quickly test on all the secondary output voltages and also make sure the G2 is stable. From the test result you will roughly know what is your next step.
I wanted to let you know that i did finally find the parts………they were manufactured by a company in
However, i have another problem that i was hoping you could help me with. I need a replacement transformer and when i look on mouser and digikey i dont see a replacment for the one i have. I noticed in your LCD repair book that i bought there appears to be (visually) an exact replacement found on page 33 at the bottom. The problem when i goto digikey our mouser is that the transformers listed have “5” leads on one side and “2” on the other. The transformer i am trying to replace has “6” on one side and “2” on the other.
Hi David H,
Usually you have to replace with the same transformer because different transformer will produce different output. My friend in
I wonder if all these courses too late for me ( i,m 50) with no background on electronics. What do you think how many years would it take “to break neck” of this profession.
As long as you have the passion and the fire in you nothing else can stop you from achieving your plan. Please read this blog post to help motivate you.
I have bought from you 2 books for components test and LCD repairs,my goal is to learn how to repair laptops.
The books that I bought are very good and helpful
Thank you very much!
Thank you Jestine I have changed the capacitor in power supply unit C1137 which filter the voltage goes to video circuitary luminance and chrominance hence the problem was solved.I pray for your long live and hope you will guide me in future on any electronic problem. Basically I am a Accountant but I have intrest in electronic and repair house hold appliences for earning some money to run my family.Please tell me any website from which I can download FREE litrature regarding repairing of TV, VCR and DVD Players.
Again Thanks a lot.
Congrat on your repair. Try this link:
Hi Jestine Yong,
I have received and read your free report “Discover The Secrets How I Repair BenQ And The Acer 17″ LCD Monitor Problems” and it’s helpfully, and you describe the steps very clearly.
I’ve plan to resign from my job and become a repairman. I’m graduated from a
Further, What I want to learn is how to fast and easily troubleshooting problems in electronic circuits like monitors (LCD and CRT), switching power supplies, PS2 concole, etc. I also want to become familiar with SMD components and learn how to exactly point to the defective part(s) where there are a lot of SMD’s components on it.
Can you help me? Thank you very much.
Thanks for the email try this website
as it has lots of repair tips in it.
If we are to take some voltage measurements do you prefer with the VGA connector plugged in or not? Will the VGA signal influence the measurements?
Yes you have to plug in the vga signal because in many newer monitors without the vga signal the power LED will turn to red indicating no high voltage.
Here are some measurements without signal I had taken:
G1 -57.2 V
G2 267.2 V
KR 70.7 – 73.2 V
KG 71.5 – 74.1 V
KB 67.2 – 69.8 V
Heater 6.41 V
How do you think of those voltages?
Seems to be good.
The G2 voltage is stable. On the CRT board I see one pin of the socket from mainboard written as 79V ( on of the secondary voltage ), but the real voltage is 89 V, sometimes will jump to almost 100 V. Do you why the voltage is higher than it should?
Sometimes manufacturer may wrongly labeled the board voltage. I have seen quite a number of board that not tally with the voltage measured. If the voltage sometimes jumped to 100 v and then back to 79v, i guess it could have problem. By right the voltage should be steady.
Could I remove the CRT board while powering the monitor on with the anode cap still plugged to the picture tube? I just want to know whether the voltage will drop to 79 V or not. The other secondary voltages are stable.
Yes you can-no problem!
Also I could hear weak sound ( tic tic ) at the CRT board. What clues can we get from the sound?
The tic tic sound could be from the spark gap (look like a small capacitor labelled as sg). Try remove the CRT board and see the sound go away or not. If there is no more sound then this could mean the CRT tube may have problem.
I took the photo again of blue resin coated capacitor with a red and a black cable which are already cut out beneath the yoke assembly. Do you know what is the original use of the cable?
If i’m not mistaken the cable could be use for controlling the raster moving right/left. If there is no cable then the raster already fixed in the center.
Could you please help me with this diode identification? The diode has a black body that measures .200 long x .105 in diameter. The anode and cathode wire diameters are .030. There is a white band around the cathode end of the diode. The following identification marks are not in-line (around the circumference of the diode). They run parallel to the axis of the diode. T 77 9.K. I cannot find this anywhere and do not know how to identify it otherwise. Your information is absolutely excellent and I feel confident in repairing the circuit board to my printing press.
Sorry never come across such diode part number, may i know this diode belongs to what equipment and what section? so that i may be can suggest a replacement for you.
i am a newly graduate of Electronics. i encounter a problem about the CRT monitor its black out on the screen but it has power, when i check the yoke in the picture tube there is no high voltage, i check the heater but still no high voltage.
i hope for your favorable response.
In order to get high voltage the flyback must receive the B+ voltage and the h.driver signal must be present at the base of the horizontal output transistor. Hope this helps!
hi jestine I hope that you are receiving blessing of god I¨m writing you because I got a trouble with a motherboard dell that when I tour on the fan of micro
begin to run very fast and I dont¨t have video I get 3 cpu with the same trouble
I hope that you can help me I will apreciate your help.
I found some bad capacitors but Istill have the problem
If after you have replaced all the bad e-caps and the cpu still would not function then i guess the motherboard may have bad ic and there is no way we can repair it because the ICs are hard to find.
I am having problem opening the your free reort on lcd and
do have adobe reader
let me know what i am doing wrong
p.s i have a LCD tv with white line horizontally at the
top of the screen, it is brand new need your help
Try off your computer and redownload again as my side here is working fine. If the lcd tv have a white line (horizontally) then this could be a problem with the lcd tv panel and need replacement.
As far as what I have read from your many explanation on your book introduction, I found out that most of the troubleshooting is about computer monitor. How about LCD TV( big screen)? Do you have e-books for it?
Normally i’m using Monitor as a guide to help out the beginners. As for the lcd tv sorry i do not have ebook on that but my repair friend Mr kent do have a membership website on lcd tv. Please visit this link:
I am looking to purchase some test equipment and am debating between the Blue ESR meter or the Atlas ESR 60.
What are your thought about the Atlas LCR meter.
I trust you opinion and appreciate your help.
I can’t give any comment on the atlas esr 60 because i don’t own one. However i do know that the Blue ESR meter have served me well and already paid itself back many times. Here is the link for the esr meter comparison:
hi mr jestine, how are you. i have a problem with a compaq monitor ( chassis km-712 ). i have found a faulty transistor ( c4632) . the role of this transistor is vetical dynamique focus. this monitor uses tda 9109 as h/v ic. as i dont have the transistor c4632 i decided to desolder it from the chassis and i also disconnected pin 10 of tda 9109 ( vertical dynamique focus signal ) and the monitor power on normally. may this create problem for the monitor. could we eliminate vertical dynamic focus function of the monitor with no problem. thanks.
I have not try this method before and after you have desoldered the pin 10 and if the monitor is working fine then you can go ahead to burn in test. If after couple of days of burnt in test and the Monitor still working good then you can conclude that the method can work and could send back to customer.
We dismantle the LCD Panel and check the back light yes we saw both sides with black dot and that confirm the faulty back light that you mentioned thru the phone, so the customer give a second set of an old panel test the LCD okay try to fix the whole unit to his CPU but not the same type, so we will try to dismantle the backlight and try the exchange method hope the backlight has the same length, Let you know after my son fixes it tonight.
Well hope it works!
Another thing we did a repair on an Khind Rechargeable Lamp ( Lantern ) found the power Transformer shorted try to get from all spareparts in town but couldn’t find one so try email Khind to find supplier for the spare but no news. Any knowledge on how to get it?
Normally this kind of transformer is customized transformer and only the supplier have the stock. However if you know the output voltage and ampere then you can buya replacement and try fit into the lantern.
Thanks alot Jestine you have been a great help to us I think it’s time that I order yr LCD E-Book with you full backing,
Thanks for your support again.
a great Joy to know you and your knowledge that you have given out. The Bible says it’s blessed to give than to receive God Bless you in all knowledge. Bye.
May God bless you and your family too!
Good evening sir jestine. thank you for this month news letter it wil be a big help for me.I would to ask a question about crystal. Does it has polarity?
No you can connect either way round.
if so? if i put in the circuit not in the same position does it affect the circuit or the crystal will have defect or become defective?
If other circuit using say 10 mhz then you can use any brand of crystal with 10 mhz and you can install in any position.
How about the nuxiel.com crystal tester how much frequency of cystal can be tested in this kind of tester? can it test to 40 mega hertz?thank you sir .God bless you.
Sorry i can’t open the website-it shows error.
By changing back light from the other LCD that is good we solved the Problem that we stated in our earlier email, at the meantime the customer says he will search the spare for the replacement onto the good LCD. I told him it’s hard to get the spare even
Good morning! Good to hear that you have solved the problem. I bought the junk lcd monitor from my computer dealers and it was about rm50.00. For your information I don’t repair notebook thus i have no idea how much it cost but you can check out from your computer dealer. Notebook usually have only one backlight but lcd monitor have two so it is more worth to buy the junk lcd monitor.
I’ve found the major problem of the display not stable ( sometimes bright then dim ), it was caused by the solder joint of the binding post of the ground at CRT board had fissure. Now the display is always ok after powering it on, but using the monitor long enough, say for more than an hour, the same problem comes again though is not that serious. Is there another problem that you could think of?.
If the G2 and G1 voltage are stable after tested with analog meter then it could be a bad pc tube.
What is the effect of spark gap problem of the picture tube may have on the display? ( assume that this monitor has this spark gap problem )
Spark gap rarely have problem, is only with the too high voltage (say more than 24 kvdc from the anode) that cause the spark gap to ark. A bad picture tube also could cause spark gap to ark too.
Another interesting point is that the display still has rainbow color only at the right edge of the picture tube even after using the demagnetizer coil. Why the rainbow color won’t disappear?
The internal tube have problem.
In my previous email ( below ) about the voltage measurement, I notice that KR, KG, KB voltages are fluctuating even before plugging in the VGA connector, why is it?
Since cpu have control over the RGB thru eeprom, it may cause the voltages to fluctuate if without signal. Try connect the VGA signal and retest it again to see if it fluctuate or not.
Now I feel that my troubleshooting skill is improving along with your every instruction, thank you very much my teacher!
No problem and keep up the good work.
In your book you mentioned that you can check ceramic capacitors with a analogue insulation tester. Is it possible to test them with a digital tester.
Yes definitely and the result is in LCD display.
My friend has a new Victor Insulation Tester Model # VC60B and is willing to sell it to me for a low price. If this meter will work I will gladly purchase it from him.
If it is possible to use a Digital Insulation Tester can you briefly explain the correct procedure on how to use it.
It can work if the spec is within the capacitor voltage range. I suggest that you test some sample cap first with your friends meter before you buy it. The way is the same with the analogue tester as explained in the ebook.
If you have other questions please do email me.
Samsung SyncMaster 920nw. Display goes out after a few seconds, can power off and on and get it back for a few seconds. Before I buy your book give some comfort if I am making the right decision. I am a computer consultant and savy on fixing things. any ideas to win my business.
There are two causes ie the inverter section and back light. The inverter section problem can be dry joints or bad components that you need to check. As for the backlight, you can take it out and see it it had turend reddish or not. If yes then you have to replace the backlight. Hope this helps!
i have problem with this one attach picture of lcd for laptop.ill check these lcd to the other laptop with the same model, well the lcd is good, but when i return back to its original the picture well like what i attach. i try put external monitor to the vga output of laptop the picture is good, what well be the problem can u help me sir? or any advice to what should i do? thanks in advance on helping me sir…
It is a LCD panel problem and very difficult to repair. The best is to replace the panel.
dear jestine im having a problem with my seleco tv 14 bs 700 chasis first there was a vertical brite line and the picture was a little small after finding a rusted pins 47uf electro cap now i still have this problem the screen is ful normal size now but the picture is white with flyback lines across any help pls thanks your faithfully Ray
I guess you have to check all the corresponding components related to the one you found 47uf cap. Try check the vertical ic as a bad ic and related components could cause flyback lines across screen.
Hello – I have a capacitor here which has failed and burst. It is 20 uF 450v +/-5% . It is quite large, about 1.5″ diameter and about 3.5″ long. It forms part of a power supply which converts 380v AC into 24v DC (13A). My question is will replacing this failed capacitor with one rated 24uF cause problems and if so what kind of problems?
If it is a filter cap then 24 UF will have no problem on the circuit.
this are all the picture I suspect is not working, I did test the 230V(AC), there is 230V but some how voltage did not get to the primary side which I’m not sure where went wrong .
In troubleshooting the power IC must have supply voltage first before anything else. Without supply voltage there will be no output in secondary side. If there is no supply voltage then you have to trace it backward. It could be an open high ohm resistor or even the ic itself bad.
I like to thank you for your technical informations.I think your guide is very useful for my technical works.How can I will be a member in your site.
You may visit http://www.electronicrepairguide.com and sign up the newsletter.
I have another problem.It is, I have a DELL crt monitor, the model no. is M570.Its red colour is more than other two clours.How can I prepare it for normal level.There is no way to get it normal by using in front menu button.I want to know how I solve this fault.
If this model does not have the RGB VR then i guess you have to reprogram the eeprom ic using eeprom programmer because newer Monitor does not have VR for you to adjust. Hope this helps!
Thank you for your reply. Your help is greatly appreciated. The diode in question is after the following components: in from wiring harness, first the negative leg on a bridge rectifier (part #4B4B41), second the negative lead on a capacitor (50V 2200uF), third on one lead of another part which I am not sure what it is (it is shaped like a resistor, pink body with one black band in the middle of it and marked “J” on the board) then to the anode of the diode in question with the cathode to a pin on a relay (part # Omron G2VN-237P 24 VDC) and finally back out to the wire harness. This circuit board belongs to a Toko 4750 printing press. If it is any help, the part number on the board is 1531-104573. The updated board according to Pro-Print carries the part number 1531-104575. Your help is greatly appreciated.
Sorry I still don’t get about the description from your explanation. Why not try this if the diode is small (like the size of 1n4007) then use UF4007 as replacement. if it has the size of 1N5408 then try UF5408.
Also, I saw you have a sight Noahtech.com and as I was reading questions and answers from another sight on the internet I noticed you closed one message with; may the Lord richly bless you. Are you a Christian? Praise the Lord if you are and I pray that the Lord will richly bless you.
Yes I’m a Christian-Praise the Lord!
Hi Jestine Yong,
Good morning to you, hope life is ok.
I have one question to ask you. Please can you show me a simple understandable method on how to use meter(DMM) to test/ check for VOLTAGE (240v ac supply dc to power IC, etc.) I still not understand it. I search on the internet but could not understand some method which they gave.
Thank you and hope to hear back from you.
Just place the back probe to the negative side of filter cap and the red probe to the power ic supply pin. Find from the internet of which pin is the supply pin. Read the result from your voltmeter.
when i test esr of a electrolytic capacitor how do i know that it is intact(good) and what is normal esr .
Intact-you can look at the capacitor pins. Normal esr have to read from the esr meter chart.
should i buy many different value of electrolytic capacitor to find normal esr?
The esr meter chart already have some reference for you.
is esr testing the best way to testing electrolytic capacitor?
Yes i use it all the time to test e-caps.
saya punya lcd tv untuk mobil(car). itu hidup untuk sesaat. setelah itu mati dengan sendirinya. lcdnya merk DIGIMAX. setelah saya periksa. Saya coba menyentuh beberapa ic. ada salah satu ic yang begitu panas. apakah mungkin ic tersebut yang rusak. saya mohon petunjuknya?
Thanks for your attention
Ya ic itu rosak kerana ic tidak boleh terlalu panas.
Good evening received one DELL PC Desktop Power supply. From 230V switch to 110V blown the power, Check all power supply section Ok pls confirm to check according to yr instruction Power Trans , Hot, Condenser, DIODE OK Now which part should I now check. Thanks God Bless.
Normally this kind of problem only involve the fuse, filter cap and the varistor. If the power transistor/s are okay then the problem could be before the power transistor. Spend more time on this area (filter cap area). Hope this helps!
Jestine good day to you,
Same to you.
I have here a Likom 17″ crt monitor model SX-775J which has a habit of blowing the H.O.T.
C5387. I measure the B+ is 55V at standby and will rise to 85V when switched on but it will pause momentarily at 75V
before going to 85V. Also the voltage after the B+ FET (IRF634A) at flyback B+ is 55V at standby mode and will rose
to 175V when on but will pause momentarily at 140V before going up.
I have changed the modulator i.c. at power supply KA3842A.
Are the above voltages normal? If not please help me fix this.
I already ring test the flyback, yoke and other coil but they seem to be good.
It looks like the B+ voltage is too high thus killing the HOT. Check the gate signal circuit of the B+ fet (IRF634A) back till the h/v oscillator ic. I came across one before (15″ likom) where a resistor value changed (located along the gate signal line) causing the HOT to blow everytime when the power was “On”.
Hope this helps!
Dear Mr. Jestine Yong
I want to know ” how to test the capacitor through digital multimeter??? ”
Will you please advise me for the same.
Hoping your sooner response.
Capacitor ( non polarity)- the best is to use digital capacitance meter
Capacitor ( with polarity like electrolytic capacitor) – the best is to use ESR meter.
Started reading the lcd monitor repair .It appears to my attention the lamp ccfl and hcfl .In your lcd monitor.you
can take a frequency meter on tap the inverter transfomer
should a reading if it is workinkg.How can test the ccfl or
hcfl are good or bad .what kind of test can you perform.
You can’ test the ccfl light with any multimeter. The best is to use other good ccfl for comparison purposes. Or you can get this tester:
Good pm sir. Do you have a circuit of tuner subber? please tell me or show me how to make it.Thanks sir.God bless you
Sorry i do not have the tuner subber circuit.
DEAR MR YONG
I HAVE MONITOR ATIVA MODEL900P MADE IN
THE PROBLEM IS ;WITH NO SIGNAL THE SCREEN SHOW MASSAGE NO SIGNAL(LED IS GREEN) FOR A FEW SECOND
AND LED TURN TO ORENAGE AND NO SCREEN.
5V O.K 12V?(MESEARED 17V) DURINGMY TESTING I CHECK THE START CIRCETE AND IT WAS OK THE SUPPLY VOLTAGE FOR THE IC CONTROLLER WAS OK (12V?) WITH SCOP I SAW PULSES IN IC 4606(2 UNIT FET IC) AND ALSO PULSES AT THE PRIMERY H.V TRANSFORMATOR.
BY MY MISTEC I MADE ASHORT AND THEN NO SCREEN AT ALL.
IC CONTROLLER IS BIT31936 OR BIT3193G.
DO YOU THINK FOR THE PTOBLEM(BEFOR THE SHORT)12V?(17V FLAT IN SCOPE)IS THE REASON .
CAN YOU GET ME PLEES SCEANATIC AND ANY DATA FOR THE IC CONTROLLER BIT31936?.
Usually if the supply voltage to the inverter ic cut off and the led turned to orange indicates problem in the mainboard (bad MCU). I have come across quite a number of this symptom in different brands of LCD Monitor.
Sorry for disturb you. I just have read you e-book. It was good and give me more information. Now I have a little confidence to check the electronic equipment. I like to know how to check and repair tv and anything else of electronic equipment. If you have the e-book let me know. Thank you
Hi Abu bakar,
If possible get a TV repair book by Homer L Davidson from amazon “Troubleshooting and repairing solid state TV’s”. Hope this helps!
I am still working on the GTC monitor, now the condition: the display is not stable ( sometimes bright sometimes dim, but display size is always the same ) when first powering it on and becoming stable after 5 to 10 minutes. I’ve double checked that the grounding cable is tight enough but still like that. What do you think is the problem, if the monitor needs time to become stable?
Use analog meter to test on the G1 and G2 pin at the CRT and make sure it is constant. If there is changes the display brightness also will be affected.
I am still wondering about the definition of B+ voltage, is this voltage only referring to the voltage entering into the primary winding of the FBT or it could also refers to another supply voltage too?
Yes voltage entering to the primary winding of flyback transformer.
When you say to check the secondary voltages, do you mean at the SMPS transformer or the voltages derived from FBT?
Voltages of the smps output. These voltages have to be steady and constant before before anything else.
I hope you are not bored with this monitor’s question. Thank you
Hello Mr. Yong,
Hopefull you are doing fine. Very sorry for delay reply your email i traveled to bush areas for long period but now am in town just want to thank you for all technical support which you always giving to me.
Best and Regards
Erick F M
Thank you for writing to me!
My current occupation is nowhere near electronics. The reason i toook your time I wanted to change it because of cut backs in our company. Electronics seemed best suited for me. But i have no background on electronics at all. And i am 50! So, how much efforts and above all years would it take to become a good repairer. Yes, i read your letters about the man who was 57. But then he had some electronic background before he just needed to improve his skills by the help of your E-Book. If i were him i would do the same. But i am late and i have no background and this reasons me out of it.
Do more practical work and never give up is the key to success. Success is not limited by age and you have to continue to pursue your dream even if it require much work from you. Try visit my website http://www.electronicrepairguide.com and sign up as a member and read go to this website http://www.repairfaq.org/REPAIR/F_Repair.html
to absorb even more electronic repair tips. If you have other question please do email me again.
Dear Mr. Yong,
We have a Toshiba 34″ CRT Television 100 Hertz, model number: 34SZ8UE.
The problem is that the picture all the sudden disappears, and there are colored vertical lines showing.
There is some sensibility in the card that when we tap the card the problem disappears. The card model is:MDFS03 3124AB.
Is there a solution for this problem, and if the problem is in this card is there a way to get this card?
If after tapping the card and the problem disappear then this mean the card have dry joint problem. Try resolder the components in the card before you get a new one. As for the part sorry i have no information as where to get this card.
Change fuse ( 1 Amp given by mistake by dealer ) On the PSU , spark burn 2 ceramic condensers, change the burn conderser and used fuse 250v 8Amp as stated in PSU board, switch on no power tested again then sparks again but not on the parts near the power section but in the SMD section damaged on smd transistor and resistor, so give up ask the customer whether to change the original DELL PSU which is I think is very expensive so ask if he prefer the standard type of PSU which is cheaper, but it will be modified outside the casing ( DELL Barebone system casing ) So any clues on the failure, because the PSU is small in size to check the parts it takes time so crowded interior. You Opinion Pls. Thanks Good Nite God Bless.
If the smd components burnt then the best solution is to get a new one because it is not easy to find the smd parts.
I’m Muhammad I from
Reference about LCD repair tips because I’m service provide electronics parts repairing.
So I have Acer LCD FP558 this problem is no backlight work.
Kindly please us I waiting you your good response.
If backlight not working make sure the inverter IC is receiving supply voltage. No supply voltage could indicate problem with the power supply or the mainboard. Check also for the condition of the backlight because if the backlight is bad the display will shutdown in few seconds.
Hi Jestine, Saya ade Lcd, Warna gambar tak sekata, adakah ini kerosakan screen
Ya kemungkinan besar lcd panel ataupun mainboard ada masalah.
I have followed your instruction to order a book for further studying.
That was good!
If the heater is AC VOLTAGE from the transformer (high ac pulse) then your meter can’t test it unless the heater voltage is derived from the secondary side of power supply. If the light of the tube glow then this mean the voltage is good.
Do you think ESR meter is worth to buy for on-line capacitor checking?
It is a must if you are serious in repair. I don’t want to do repair if i don’t have ESR meter because i don’t want to guess if an e-cap is good or bad. Get one and you will love it. You may visit this link for more information:
hi jestine yong
i am ibrahim if you dont remember me i bought two books from you how to test electronic components and the lcd one.
i have got a small problem ,i found a FET shorted on a motherboard and i want to replace it but i did not find the exact number could you tell me where i can find equivant one , is there any website that tells the equivalant fets to any fet , the one i am looking for is fds4435bz it is a fairchild semiconductor
many thanks for helping me
Yes i remember you and you can visit this website to get the parts at
When I need to disassemble the mainboard of monitor, what is the best way to support the falling picture tube ( its neck will come down to anywhere on the mainboard ). This problem really annoys me when I need to take out the mainboard to replace some components.
I place the tube face down a square sponge and do all the voltage testing and even replace the components.
About the GTC monitor display is still not stable ( sometimes bright & sometimes dim ), the G1 and G2 is solid enough ( plus minus 0.2 V ), and as I had told you before the spring ground of the picture tube is not connected to main& CRT board ground, hence in the photo of the CRT board, they are referred separately as GND2 and GND1. Do you think it’s a good idea to joint them, would it be too dangerous?
If it is a different ground then you should not join them but to my knowledge i have never seen a CRT that have two separate ground. In fact you can compare GTC with another CRT Monitor for reference purposes.
I’m now working on 17″ Logix LGX17H which display is not able to see without turning off the lighting of the room at night. And after checking finds G1 58V, G2 583V, Heater is only 0.1 V, but I could see the glow of the neck is bright enough. Is the bright glowing of the neck of the picture tube has nothing to do with the heater voltage?
In fact you can trace the heater to see where the source from. From flyback or from secondary side of power supply. If it is from Flyback then expect no or low voltage reading from your meter and if it is from the power supply then you may have wrongly check on the heater point.
Why are the designs of monitor could be so different? ( in terms of the cable running from the spring ground to CRT board & mainboard ). You have seen the photo of GTC monitor I sent you, where it has only one cable running from spring ground of the picture tube to CRT board, haven’t you?
If the cable running from the spring ground to the CRT board ground then it is indeed the cold ground. And the CRT board ground have connection with the earth ground. But you told me that there was no reading between the cold ground and the spring ground-i was wandering?
While in other case ( LG studio works ) I see there are 7 grounding cables reaching from picture tube spring ground and mainboard to the CRT board. If I forgot to connect them back ( 2 of them for instance ) in the troubleshooting process, would it be dangerous?
Yes the CPU may blow. I have made this mistake on Samsung Monitor and it spoilt the CPU IC of the Monitor.
The LG studio works monitor I’ve confirmed the problem is the internal capacitor of the FBT has dropped to much. But before the monitor is able to be turned on and now after assembling it back and rechecking all the components ( especially the primary winding of FBT and even replacing the HOT) and cabling, the monitor cannot be turn on, only the function leds are flashing. My question is could the bad internal capacitor of the FBT preventing the monitor to be turned on?
You have to check the internal capacitor with analog meter set to x 10 k ohm range. If there is a reading then the capacitor is shorted and will affect the Monitor smps.
I’m now enjoying reading the “Computer and Video monitors” by Sci.Electronics.Repair. In on of the articles they are using the word “D.O.A”, do you know what does it stand for? and another word “fusible resistor/ flameproof resistor ( FR )”, but so far I haven’t seen one, what is this component?
D.O.A stands for Dead On Arrival and my former computer company always use this word to send a feedback to
Thanks a lot Jestine… the problem was that i understood 1000V would cover 250V, 500V and 1000V, but you are right because this one doesn’t show anything like that… i found another one and it has the ranges of 250, 500 and 1000
Yes you should look for few ranges one.
i want to ask you something else… have you noticed the diodes in any circuit board(logic board from flat screen monitors, modem cards, radios,etc) i call them “mini diodes” they don’t have any number or spec, usually are redish or orange, little ones kind of like crystal material, surface mounted. I know the they differentiate them between plain diodeand z-diode by a the color band and i don’t know if it is satndard or not… some time have a hard time getting their real value because i don’t know if they are swithching diode or volatge suppressor, (i know that there are more than that)… any advise would be trully appreciate it… thanks a lot my friend and have a great day…
In fact i’m also facing the similar situation because the manufacturer did not give us any reference for that. If the board is labelled as ZD then we know it is a zener diode and if it labelled as D then we know is a diode. But what type of diode is that? Normally i would just put in a signal diode with the part numebr 1N4148 to test out the circuit. If it still does not work then i will use a bigger diode (UF4004) to test out the circuit. Hope this helps!
I already downloaded your report. thanks for your feedback.
but now I a have a problem.I hope you will help me to solve it.
I have a 48V power supply, when I power ON the p/s it become trip the building.
I already check the capacitor, diode, mosfet & others component.All the components is in a good condition.
So now, what is the suspect from the p/s. I hope you will help me to solve this problem.
Trip the buiding? then i guess there must be something shorted between the ground to live or ground to the neutral line. Remove the power transformer, power fet and bridge rectifier and check the line again with your analog meter set to x 10 k ohm between the live, neutral to ground. The pointer should not show any low ohm reading. The putting back one by one the component you have taken out and see if the short will come back or not. Check also for varistor located at the input side of the smps as it is prone to develop short circuit when check with x 10 k ohm range. Hope this helps!
Hello Jestine, I have been reading your article about LCD BenQ 17″ (Problem in C5707 Transistor in BenQ T705 LCD Monitor) I’m trying to repair the BenQ FP731 LCD Monitor, with the same problem about C5707 and I have 3 questions,
1, when you said “check the tuning capacitor for high ESR value” I do not know which one are you talking about,
The cap that is located nearby the high voltage transformer. It has the value from 0.15 uf to 0.22 uf 160 to 250 volt.
2. I can not find the transistor C5707 in Digikey, so have you a provider for this component?
3. There is an other damaged component for this problem. (no video or not backlight)
Make sure there is output voltage from the power supply. If there are voltage then check and make sure all the voltages is reaching the mainboard. If the mainboard got all the voltages then suspect a bad mainboard.
Thanks very much.
P.D. very good article, well done.
You are welcome.
Jestine, I’m in a great problem. one of my IPS has created an inductive way with its metal cover. somehow 220V~ is obtained at the surface of the casing,but it just giving electric shock for a seconds and can’t run any load. I found no connection like that. but some loops of coils of the main inverting transformer is open. that transformer is of 500W/12V center tapped. I’ve used MOSFET(IRFZ44N) at the output section. can you help me about this problem? or have you any experience like this inductive way??
Sorry no experience in the inductive machine thus i could not give any expertise advice on this matter.
It has been long when i wrote to you,help me my tv developed a faulty its a grudig make,when you switch power on the led for power mode comes on and off within a second,checked the ht seems to have faulty,no rust,screen off or not coming on have used it for the past more than 17years.what can be the problem have tried charging the componets arround but nothing,grudig spare to find its a problem what be replaced?
Your problem could be in the power side ot the high voltage side. Visit this website to learn how you can isolate the tv problem at:
good day sir,
i have being tring purchase the e-book on LCD TELEVISION REPAIR but there seems to be a problem doing so, either the site isnt real or some other people are tring to defraud me. is there anyway you can be helpful in assisting me with the transaction as i have more confidence in you or am i to believe the site dosent exist.
i remain to hear from you soon
Sorry the website does not belong to me. it is belong to my repair friend Mr Kent and you can email him at fastrepairguide(at)gmail.com. By the way Mr
Can I use the MJE3055TG instead C5707?, my local provider (Digi-key) do not has C5707 and get it from
The best is still use back the original part number and you can order it from http://www.bluestar-online.com
If you have other questions please do email me again.
Thanks for your help. Turns out that once i removed the transformer i found that it was ok………it was another device that was causing the shorting.
Okay got it
However, i do have a new problem. I am working on a westinghouse lcd L2046NV and it wont turn on. I have followed your repair manual and i did two caps that were “bulging” and a fuse open. I replaced the caps and the fuse turned on the lcd and ……… nothing………i checked the fuse and it was blown again. I replaced ALL the caps and the fuse for a 2nd time and turned on the lcd and again the fuse opened up.
I cant seem to find the short. The power supply and the inverter are on the same board. I removed the board and shorted the blown fuse hoping to find a hot spot and measure the current………..but there was no current through the fuse………….
?Does the board i removed need to be plugged into the “lamps” before current will flow through the fuse?
No it is not necessary to plug in the lamp for testing.
?Any ideas on how to find the short?
Yes, compare the resistance of the top lamp components and the bottom lamp components. Particularly look for the semiconductor like IC, transistor and diode. Any different in ohms reading indicates there is a problem in that section.
?Also, i read a post you did (https://www.jestineyong.com/?p=1297) and you referenced part Bit 3713………….do you have the data sheet for this?
Sorry i do not have that ic data too. Normally inverter ic is very reliable and rarely have problem.
I know your very busy but if you can help it would be appreciated. This monitor is a tough one………just cant seem to find the short.
Its okay no problem if you still have any questions just email me. Have a good day!