Electronic Repair Questions/Answers & Testimonials Part 15
Hi Mr. Yong,
Kindly help me to solve the below mentioned problem:
The protective fuse of my D.C power supply has blown off, I just changed
it but it again blown off. How can I check my D.C supply to trace this
With Best Regards
Usually the fuse blown could be cause by a shorted bridge rectifier or the power semiconductor like power IC, power FET and even shorted diode in the output side.
you pl don’t confuse my quotation is bellow.
1) How to check anode cap voltage?
Because flay back transformer other points voltage is OK. (G1,AFC & B+ in & Collector horizontal out put voltage. but how to check the anode cap voltage because this voltage is very high voltage.
pls adv me.
thanks for the you send your details.
You need a high voltage probe to check the anode cap voltage.
i have a lg studiowork 500g monitor 15″ . In this monitor no display and give us a power light blinking in two colours yellow or green. Please help me sir for solve this fault.
Check if there is anything shorted at the secondary side like output diodes and horizontal output transistors. If you have the blue ring tester you can test the primary winding of flyback transformer and also the horizontal yoke coil.
Nice to know about your background in electronics and my family is doing fine-thank you. By the way here is your questions and answers:
Dear my brother what am i looking for is advance meter so that i can be able to check ic if its working or not. Is it possible for me to get it
You need an oscilloscope to test the IC out. Get the spec of the IC and check the input and the output waveform.
and i want to know if you have a branch or Agent here in
Sorry i do not have a branch in overseas.
Yes I already read your report about electronic repair. its very helpful, sir i don’t know if I ask this question regarding x-360 problem to you, what normally happen if he x-360.have three red lights or they call it 3rl?
Sorry I don’t have the chance to fix this Xbox in my country thus I can’t provide you any expertise advice about this matter. However you may visit my blog here at https://www.jestineyong.com/?cat=32
where the owner of the eBook has the solution for it. Have a good day!
There is marking on the diode 7S9 on each of the diode
please kindly tell what does it means or there is any supporting documents on the device markings please help me sir.
Please check on this link:
Sorry no data for the second one.
if you possible you pl send this type checking photograph other video help for my references. Because first time I check this high voltage.
You may visit this link:
I would like to ask if you can help me find an e-book on how to fix TV set I am very interested in finding a website like yours on how to fix CRT TV sets. I am a beginner in the electronic field so I just want to find this kind of books.
There is a website http://www.monitor-repair.com that sell eBooks for many electronic equipment. However I got feedback from my members saying that their information is very basic. Why not buy a physical from amazon.com in TV repair. Recommended TV repair book is “Troubleshooting and repairing solid state TV’s by homer L DAVIDSON”. This is the best book in TV repair. Hope this helps!
Thank you for email Jestine. I apologize for the delay.
I need a meter that will read very low pF’s and over 22,000uf’s in the capacitance measurement range. The Peak Atlas ESR does not meet the requirement, though the Peak Atlas LCR is closest. This is for very old high voltage electronics with very low to very high capacitance ranges. Do you have any other suggestions or recommendations.
Try sencore website at http://www.sencore.com/products/general-test-measurement-equipment/75
But the equipment is very expensive.
Yeah I did. I have another question, besides repairing; do you do any electronic projects, like robots and stuff like that?
Besides the repairing job, i do teaching and writing books.
What about RF? Do you know anything about that?
No time for the RF. It is in different field. I’m more on the CRT/LCD Monitor and SMPS repair.
How do you think I could get my own little business started? Where could I find things to fix? Who would I go to for that?
Start from friends and relative telling them that you do electronic repair service. I suggest that if possible you get some experience working for others maybe half to one year time before you come out on your own.
I’m having a hard time trying to find a good website where I could find all the schematics I need for any consumer electronics repair. Do you know of any?
What did you have at your first work bench?
Blue ESR meter
Blue Ring Tester
High voltage probe
Digital Capacitance Meter
Inductance meter and
It depends on what field you are in. If you are in satellite repair, you may have to get a satellite test equipment and etc
They have oscilloscope programs on lab tops, do you know if they are any good? Do they have limitations?
Sorry i don’ have any of this. I only have the analogue oscilloscope.
Here is your questions and answers:
I am repairing a Fax machine Ricoh 500, and there is an IC (SIL package) with p/n NEC NLS-11, two pins found shorted (2.3ohm) I am not sure this IC really faulty or not since I can not found its datasheet and these 2 pins are parallel with a 50Vdc electrolytic capacitor which should not be in short condition. I want to take risk to change the IC but it is not available in
Sorry Yong, i could not get the IC and the datasheet too. In your case could you take some photo shot and email me for further analysis? It’s hard to picture your description. Have a good day!
I have a 235Watt SMPS PC PSU.I like to make the PSU as a separate PSU for Linksys modem. The modem says that it requires 12V at 1A DC. Can I connect the modem directly to the PSU’s 12V rail?. Does it damage the modem? Or do I need to add a current limiting resistor? If I need to add a resistor what is the value? What is the power of the resistor I require?
I doubt that the pc power supply could work due to the fewer loads in the modem. The power supply may go into shutdown mode. Unless you have a used motherboard (load) and tap the power supply voltage to the modem but this look a bit ugly where beside the modem there is a used motherboard. Can you confirm whether the power supply could run without load and the output measured is exactly 12 Volt?
How do I have to connect it across the +ve and -ve (or) in series to the +ve to which the modem is connected?.
Yes just tap the positive voltage of the 12 volt and connect to the positive side of the modem (there is no current limiting resistor required) and the negative (black wire) to the negative side of modem.
Hello, I am interested in your LCD Monitor repair guide but I would like to ask one question. What electronic equipment is needed in order to repair a monitor?
Here are the test equipment that can help you to repair the CRT and LCD Monitors:
By the way, do you have experience in electronic repair? If you do not have and wanted to learn more in the field then i suggest that you visit http://www.TestingElectronicComponents.com
I try to fix LCD monitor Hp model PE1238 17″ with no display when plug in vga cable signal into it. I checked all the e-capacitor, some capacitor was bad. I replaced all the capacitor even not bad. But the problem still cannot solve, when plug in the vga signal, the display show up “monitor going to sleep” and 3second power led orange standby mode with no display. Help.
First check that the h and v signal present from the computer to the Mainboard. If either one of the signal wire broken internally, the message will come out. If both the signals present in the mainboard then suspect a bad Mainboard. Is all the output voltages from the power supply are within range?
Here is your question and answers:
I hope that your are doing well with your daily activities.
I’m fine thank you!
I visited your website and i read a lot of email (testimonials) from different people of different places. I wish i could get your E-book it seem it has a lot materials on how to repair LCD monitors most of LCD monitors are like LCD TV. I tried to find your book from different bookshop i can’t get it.
My book is an eBook thus you can’t find it in bookstore. It is only available online.
Can you tell me its how much and if possible i can order it.
The price is USD47.77 and you can order and download it from http://www.LCD-Monitor-Repair.com
Here is your questions and answers:
I am a graduate of electrical engineering with passion for electronics but lack practical experience,infact i can not solder a component not to talk of building a circuit. now i have a dream of having my own electrical/electronics company in the nearest future.
Nice to know about your background and your plan
Do you think this your book can help to achieve my dream? and what other advise will u like to give me that will serve as guide. So that i can become an electronics repair expert.
My ebook Testing electronic Components is the first step to achieve your dream. You must be good at testing electronic components in order to repair equipment. Once you are strong in testing electronic components you then can proceed to get my another ebook LCD Monitor Repair. Both eBooks could help you in a fast way to become good in electronic repair. It depends also whether you are hardworking or not and etc.
also i want you to please link me to another site where i can get information on troubleshooting electrical appliances.
Try my other website at http://www.electronicrepairguide.com
Have a good day!
thank you for your letter I have to buy 3 of your books but i just start to save some money for that.
Take your time-no problem!
in other case for the lcd tv samsung le46m86bd which i told you about (its the first lcd tv to repair for me)i make some testing and i find this results .in the left inverter we have A358 with 8 pin one pin change from 7v to o when the backlights are off after 2 second after tv is on. we have BL-1040 (transformer in the inverter)who has got a pin FB this FB leave the inverter to the power supply to the CT-27 .all voltage are ok just in the feed back (FB )we have nothing ov .what do you think .thanks a lot.
If the supply voltage change from 7v to 0v then trace back circuit to find out why the signal stop. In LCD Monitor if there is no signal this clearly indicates the problem of a bad MCU. Without this voltage the backlight will definitely shutdown.
How r u. I am very sorry that i didn’t reply to
I am waiting for
Please visit this link for more information :
I agree that it is worth it if you are repairing tv’s and Smps. Here is some food for thought. If someone comes out with a book or video for repairing LCD monitors without the need for extensive test equipment, they would have a gold mine in sales.
I wish i could do that but the fact is that electronic problems are very dynamic and have to depends on different types of test equipment to repair different problem. For example-Blue ESR METER for checking electrolytic capacitors, multimeter to test on voltage, current and resistance, scope to test on waveform and etc. In electronic repair we cannot guess and we have to be certain that the components indeed have problem (with the help of test equipment) so that we can replace the components and retest the set again. Have a nice day John!
how are you?
I’m fine thank you!
i have a question and i believe you could help me fix that. i always come across a problem that i don’t have idea to deal with after trying what i suggest to do.
Well, i usually come a across a fault on many DVD/VCD player that cannot read all DVD/VCD. I use CD cleaner with no success and open the cover then use cotton pad to clean the Laser/sensor lid but still i don’t have a good feedback.
my question is:
1. is there any other way i can do with such fault apart from using cd
cleaner or cotton pad
This is the common way of doing it but your problem is not about the dirty lens
2. The laser/sensor lid can be replaced with any other one
Yes but has to be the same part number although it is from different brand. The electronic suppliers know the best
3. This problem comes from the laser/sensor lid itself or other
surrounding component or a board
Most probably from the lens itself
4. How can I test the laser/sensor lid
Use a laser power meter. Try visit this link
I’m amazed and overwhelmed about your offer of learning the easy and accurate testing and troubleshooting of electronic parts. I have so many questions that I’m still searching on. Can you teach me Sir?- the easy way and well explained testing and troubleshooting of electronic parts like capacitors, transistors, resistors, diodes, integrated circuits, filter capacitors, relays, cd / dvd lens repair, etc.
Thank you so much! I will be waiting for you response.
All these testing i have compiled into an ebook at http://www.TestingElectronicComponents.com
You may subscribe to my other website at http://www.electronicrepairguide.com to read some of the good repair articles there. Have a good day!
The h and v signal is present in the mainboard, so if this mainboard bad, can this mainboard get fix?
Normally can’t, due to no spare parts available.
what cause the mainboard will faulty?
Too hot, components itself quality is no good
How to test all the output voltages from the power supply are within range?
If you get 5 volt, 12 volts, and etc then you know it is good because IC usually need 5 Volt to run. In your case i think the power supply is okay because the LED is lit.
I got tested power on LCD without plug in vga signal , the display got something show up “Check Signal cable”. Then after 3second will disappear and LED become orange standby mode with no display. Will inverter board got problem?
Normally when inverter got problem the LED is still green and not orange. Do you get supply voltage to the inverter IC?
hi Jestin Yong,
I ‘m reading “test electric component”. you can for me know, if coil shorted, how i test? Because if i use analog meter, set X1, i put 2 probe into 2 winding coil. the meter show continuity. The coils short or ok are show too. i don’t have inductor tester or flyback test. thank your very much.
For a small coil you can always use analog meter to test it but for coils that have many turns (windings), you have to use a coil tester like the Blue Ring Tester at http://www.electronicrepairguide.com/blue-ring-tester.html
If you have other questions please do email me again. Have a good day and thanks for your support on my ebook!
But the problem I’m encountering now is the no display problem. And some buzzing sound around the CRT board area when i on the monitor.
Does the Monitor generate high voltage (when put your hand near to crt tube-there will be a pulling of hairs). If no then you have to check the b+ VOLTAGE and make sure it is present. Sometimes the buzzing sound could be from the SMPS section. What is the colour of the LED LIGHT (amber or green) after power On?
I’m currently fixing a china model TV which has power problem too. The fuse keeps on blow as soon as I’ve replace with a new one and turn it on. What could possibly be the culprit? Thanks!
It could be a shorted bridge rectifier, power fet, power IC, shorted primary winding in transformer, shorted secondary diode and sometimes a shorted posistor could cause it to blow too.
Anyways keep up the good work!
Same to you!
When troubleshooting the power supply / inverter board and you have a radial filter capacitor and the pins are only exposed on the bottom of the board. What’s the best way to get to HOT GROUND to make the tests? Your book shows the filter capacitor with the pins exposed and easily accessible. Mine is a flush mounted filter capacitor and you can only get to the pins on the bottom of the board.
You may solder out a wire from bottom but be extra careful about that wire. I do that too!
Where else can I find a hot ground and be sure its hot ground so I don’t destroy my meter?
Any solder pad along the negative side of the big filter capacitor. Once you have located the solder pad, try seeing from in front if there is any free space for you to put in your black probe.
Can I remove the board and make the measurements?
You may make the measurement with the board removed but again be extra careful about it.
or does it need to be screwed into the LCD and grounded?
It depends on LCD Monitor designs. Some have the ground connected to every part of the board while some do not have. However it still to safe to put the black probe to hot ground even though there is no cold ground because both are going to different circuit.
Thanks in advance for the help.
No problem! If you still have other questions please do email me again.
Have a good day!
VERY VERY THANK U SIR
sir in 500g monitito solve fault in this monitor i have faulty tda4841 and solve it.but in this monitor another fault. when we touch menue button then oprate OSD but this language is not clear it show only diffrent logo please help me. in monitor S3C863AXZZ-AQBA micom. and how to write micom by softjig.
It could the fault of corrupted of eeprom data, bad crystal or even bad MICOM. Sorry i do not have softjig or even even software (program) for this Monitor.
I purchased your repair guide. Nice job!
Thanks for the support!
I am repairing an inverter board for a laptop lcd display. I found an open smd fuse and a shorted cmd capacitor. The fuse is marked “TN” and the circuit board is labeled “F1”. I looked up the code and I believe its actually a transient suppressor. The amperage rating is unknown.
I’m not sure about laptop but in LCD Monitor the inverter fuse have ampere rating between 2 to 3 amp. You can try 2amp to test it out first.If the board labeled as F1 then most probably it is a fuse and not transient suppresor. Do you mean the code “TN” stand for transient suppresor? I wish to know too because i may support notebook repairer also.
The capacitor has no markings so I do not know it’s value or voltage rating. No schematics are available for this board, part # DAC-08N006.
Is there any same capacitor type of capacitor/same color in the inverter board? If possible you could take some photo shots and send it to email@example.com for evaluation.
How do I find what these component are so I can order the parts?
For future reference you may visit my blog list of electronic suppliers at https://www.jestineyong.com/?cat=12
Here is your questions ans answers:
I NEED TO KNOW HOW TO TEST TRANSISTORS USING A DIGITAL MULTIMETER AND AN ANALOGE.
All these testing components i have compiled into an eBook at http://www.TestingElectronicComponents.com
I ALSO NEED TO BUILD MY PROJECTS ON A BREAD BOARD BUT GET CONFUSED WITH
As for the breadboard try visit this link :http://www.kpsec.freeuk.com/breadb.htm
I AM LOOKING FOR CIRCIUT DAIGRAMS ON PARK DISTANCE CONTROL AND
TIMING CIRCUITS. PARDON MY SPELLING.
Sorry i do not have such diagram.
I hope this letter finds you in good health.
Since you are more experienced than I am. Today I am asking you for some encouragement, & constructive criticism.
I often have to figure things out on my own, & sometimes I feel very NERVOUS about my chances of success. Could you please spare some time to read & comment on my repair setup plan? I am only part way through implementing it. & am nervous about whether I am doing the right thing.
The basics are as follows:
1. Acquire Digital Camera.
2. Acquire ESR, DMM, & Analog meters.
3. Acquire Oscilloscope.
4. Apply checks to determine proper wiring of ACV outlets. (re-wire if necessary)
5. Apply continuity checks to determine which circuit breakers control workshop ACV outlets, & which circuits are branches off single outlets. (re-wire if necessary)
6. Collect Datasheet information on components that are strange to me when I open a chassis.
7. Collect information from engineering component supplier (e.g. Globalspec) on different components. (create glossary)
8. Create & print a table explaining values of capacitor codes (i.e. polarized & non-polarized)
9. Create & print a table of commonly used components & their commonly seen values; which I encounter in my repair work.
10. Create & print a table of diagnostic tests & routines that can be done with Multimeters
11. Create & print a table of electronics notation. (i.e. letters associated with units of measure)
12. Create & print a table of Tools to be used & when. (i.e. by purpose or repair type).
13. Create & print a table of unit conversions (e.g. Pico, Nano, Micro, etc.) by exponent & decimal point position.
14. Create & print a table of warnings associated with handling of different components.
15. Create a digital photo gallery of damaged components.
16. Create a digital photo gallery of different components (i.e. common vs. exotic)
17. Create form for recording workshop lessons learned. (i.e. speed repeat problem solving)
18. Keep record of what electronics formulas were helpful during problem solving.
19. Practice using diagnostic equipment, & record results.
20. Print out the Resistor colour chart.
Jestine, where I live due to power problems we frequently have damage to electronics & electrical equipment.
Many people (those w/money) are interested in purchasing alternative energy (Solar,
I believe that until the circuitry is all multilayered PCB, I can supplement my living by focusing on the repair of this damaged equipment.
Already, I have been asked if I service CRT & LCD monitors. I have been honest & said no, but maybe I will offer as a service next year. (2009)
Jestine as you have suggested, I am trying to focus on one area (i.e. power protection) 1st, then move on.
None of my family knows what to make of my choice of career, my dad was encouraging me towards being a respectable accountant.
Many businessmen here (
What repair is done, tends to consist of swapping out entire boards imported from overseas (i.e. primarily
When I find an area of repair cash cow, I may have to import parts that cannot be located in local electronic part stores, so my charges will have to support this aspect of my business.
Thank you for writing the article on pricing.
Jestine, from your experience, does it sound like I am on a sensible path?
Look like you are a perfectionist and the list was superb! Its good to carefully plan all this as running a business needs lots of preparation, time, money and energy. Take one step at a time so that you can gradually progress to achieved your dream. Be good at power protection field first before jumping to another field. However along your journey if you have any difficulty in electronic repair, you are welcome to email me.
How to fix a PC Power supply?
You need to start from basic first as fixing a power supply involved electricity and understanding of electronics. Get my other eBook first http://www.TestingElectronicComponents.com . Once you are strong in testing electronic components and know about the safety in electricity you can start to work on any electronic equipment which include the pc power supply. If you have other questions please do email me again. Have a good day!
Here are your questions ans answers:
Thanks for the quick response. I soldered out a wire and made the measurements on a Dell 15″ LCD. All the measurements in your book showed good on the power supply / inverter board combo but I still have a white screen. The logic board is good because I have a good working power supply I can put in and it works fine. I put in the other bad power supply PCB and get the white screen. Even the voltage regulator on the logic board has correct voltages; all the IC’s have correct voltages on power supply, all capacitors check out good with my ESR meter on power supply. Also I was thinking about buying a Huntron Tracker 2700 or 2800 signature analysis device, are you familiar with them? Do you recommend them?
I have the huntron 2000 and rarely use it. But the 2700 and 2800 model can be use to test certain electronic components on board without removing it. Both are quite costly and you have to justify if it worth to invest one or not. In LCD Monitor repair especially the mainboard and the lcd controller board, even though you could locate the defective IC but because the market don’t sell such IC,s we still can’t solve the problem. If you buy the huntron for other purposes besides lcd monitor repair then you may get one.
So if the voltages are good to the inverter, inverter IC, filter capacitor, capacitors have good ESR, Secondary side Diodes have correct voltage, Full bridge rectifier is good, transformers working correctly with proper frequency, the lamps are coming on ok. What components do you look for next? Hard to know where to start when all the voltage test points check out ok. I just get a white screen.
If there is signal present in the lcd controller board and the smd fuse in the lcd controller board is okay then suspect a bad lcd controller board (lcd panel). If there is no signal (have to test it with scope) out to the lcd controller board, suspect a bad Main board. You must have voltage into the lcd controller board (1.8 v or 2.5 v depends on model) otherwise there will be white screen.
If you have other questions please do email me again.
Have a good day!
Jestine, I am working on a 3 phase Toshiba brand (G9) drive which came in to my shop for repair. The customer complain is that every time he powers-up the drive, the fuse blown. I static check all the phases from the input side and the output. The output side checked fine but the input from the positive side checked bad. I opened up the drive and found out a bad bus capacitors. I changed the bus caps and still having the same problem. I checked the input bridge rectifiers which is the SCR and three of them firing good. I am still not getting a bus voltage. What can you tell me at this point to check. By the way, the output (inverter) side is IGBT. The drive is 3 phase 460V.
Honestly i have never repair such equipment before thus i can’t give any definite answer to you. However if possible try take some clear photos on few angles of the circuit board and send it to jestineycs(at)yahoo.com for evaluation. Once i have seen the photos and if i have any ideas i will let you know. Have a great day!
Hello Mr. Jestine,
I know you are receiving a lot of emails, so I’ll try to keep this short.
My lcd monitor started to switch off after about 3 to 15 seconds of working. Before that it was also showing a vertical stripe of noise about 2 cm wide.
I opened the lcd and pressed/tapped on various parts of the controller board (mainly the cpu).
Now the stripe has disappeared but the LCD still turns off after about 3 to 15 seconds of working.
If I press the input select button 2 times, then it comes back for another 3 to 15 seconds.
Sounds like a capacitor of the power supply to me. Any suggestions?
When you said it started to switch off you mean the display or the power? Is the LED still ON after 3 to 15 seconds? It can be also capacitors especially the capacitors that has bulged! Bad caps could also cause funny display in the screen which include the vertical stripe.
Have a good day!
I have just purchased your LCD repair guide online and followed the procedure to work on a DELL E172FPb. After testing from the beginning, the bridge rectifier has good reading, the filter capacitor has good reading, and then tested the VCC, I have found the VCC reading is a little lower than you instructed (10V instead of 16V-20V). Does this mean the root cause is the VCC or there might be something else to cause the power light blinking? Thanks in advance for your kindly attention in this matter!
It depends on the power IC part number. What is the ic part number? Have you check the secondary diode for shorted reading as this could cause power to blinks too. Sometimes the power LED blinks could indicate problems in the Mainboard. What you need to do now is to test the secondary output with analog meter to see if the pointer stable or not. If it not stable (pointer going up and down) then most probably the problem is in the power supply section. Check also all the filter electrolytic capacitors for any high ESR reading.
Have a good day and thanks for your support on my ebook!
So the you can get all the components for the power supply / Inverter board but you can’t purchase certain IC’s on the control board? Do the manufacturers not sell them to prevent us from repairing the control boards?
This is true especially the scalar and the lcd controller IC. For the MCU in the mainboard, some company are selling it but it has no program in it (blank data) and you have to get a special programmer to program the data on your own.
So the only thing you can repair is the power supply and inverter boards?
Not only that, it includes the front panel board and backlight and intermittent line problem in lcd panel.
You have to replace the control / main board if you identify a failed component on the control board?
If the scalar IC have problem then we have to replace the board unless you have a similar ic on a used board where you can salvage it. If the lcd controller ic have problem then we have to replace the whole lcd panel. Sometimes a mainboard have problem not necessary must be the IC have problem, it could be a bad voltage regulator, defective crystal, shorted smd capacitor and also smd diode.
For your information, this kind of problem could happens to LCD TV too.
Thanks again for your help, kind of you to help.
I have played with electronics since about 1964, use to be tubes then. There has been a great love and enjoyment at times in repairing things. Have a general knowledge how to use test equipment. I have two switch mode power supplies which go to CO2 lasers which no longer work, I do not have the knowledge to test the chip circuits in place to know which one needs replacement. Can you tell me how? I will pay for this information. Or can I send you these two power supplies to repair. I anxiously await your reply. Thanks again
Nice to know about your background in electronics. However i guess i can’t accept the power supplies because i’m not base in
i have another question. I have a dell 17 inch tft monitor 1703FPs with a backlight problem. The backlight is only 0.5 seconds on , then turning off.
i checked the power supply but couldn`t see anything wrong. I checked with a 12 volt light and the light is bright on the 5 volt line,but not bright on the 12 volt line and the voltage is dropping to 3-4 volt. Does this mean there is a problem with the 12 volt line and do you maybe know what can be the problem? it has an inverter on seperate print and only 1 ccfl light does lit. The voltage (12 volt) is not dropping when inverter is connected. i try to measure the voltage on the inverter ic. i`m not sure wich pin to measure. it`s Bit3106 IC . i measure on pin AVDD and PVDD and i measure 5 volts.
I think this is not good voltage? (it must me 12 volt?) In your ebook you writing about a 24 volt brake light, do i need to use this instead of the 12 volt light?
Some inverter ic need 5 volt to power up. Observe to see if this voltage drop or not when the backlight goes off. Test it with analogue meter which is faster in capturing the voltage result compare to digital meter. If the voltage stable then suspect problem in the backlight, high voltage transformer area and components or even a bad inverter ic itself. If the voltage drop, then trace back to see if the start circuit components or the mainboard haveproblem or not.
In you case of replacing the light bulb, if it drop to 3 to 4 volts this could indicates the power supply is not good in sustaining the load. Most probably it could be bad esr in e-caps, bad current sense resistor or even the pico fuse. If this model have pico fuse make sure you test it with analog meter and the pointer should move up till the right end side of the scale. By the way if the voltage is 12 v then i suggest that you use 24 volt bulb if not it may blow the 12 volt bulb.
I stored this on my computer as a PDF file along with the bonus text you included when I paid my subscription for fixing LCD monitors. It was helpful in fixing 2 Dell 17FPxx flat panel monitors. Went right to the CCFT inverter transistors and replaced them all with new ones off Ebay for 9 US Dollars. Monitor came right back up and has been solid ever since. It was a great report.
hi, mr jestine, how are you. about the monitor that i asked you that it has dim screen. i told you that that sda line vary between 1.5v and 3v, but i missed to tell you that this happen only when vga cable is connected to the pc. when i disconnect the vga cable from the pc, the sda line is good ( 4.7v). does this mean that memory or microprocessor are bad ? can you tell me more. thank you very much mr jestine.
Its hard to say, try remove one by one the ic in the monitor and retest it. Nowadays video preamp, h/v oscillator ic, are also connected to the sda and scl lines too.
I got the pictures thanks!
Should I assume that there is something wrong with the high voltage unit? If yes, what do you recommend to check?
If it turns off after 3 to 15 seconds then first you need to make sure the inverter ic is still receiving the supply voltage after turned off. This supply voltage is the test point to confirm if the inverter board itself have problem or the Mainboard.
If the display goes off and the voltage is still present at the input of the inverter ic then suspect the inverter board have problem, possibly could be one of the backlight have problem too. If the voltage shutoff when the display go off then suspect a missing On signal from the mainboard, normally this “On signal is coming from MCU. I have came across many similar problem in SAMSUNG LCD due to a bad MCU that causes the inverter to shutdown.
Good morning sir,
First of all I got your email address, really I have read your website since one week, it is really amazing thing to learn electronic and as soon as professional.
Really sir I need your help actually iam in computer hardware but l like to learn electronic devices like monitor, LCD , laptop , so please I need your professional guidance to learn electronic to find out exact part their identification . free learning books.
My cat just accidentally toppled over my ASUS 22 inch monitor. It is
just 2 months old!! The glass screen has a pin-sized crack. However, the
whole screen seems to be worthless now. I can’t see anything meaningful
on the screen. Some people only have garbled display on the area with
cracks but my whole screen is garbled. What do you think is wrong with
my monitor and how can I fix it?
If you were to fix it, how much would you charge?
I guess the internal part of lcd screen circuitry could be affected and only replacement could solve this problem.
I managed to solve the problem of the display quickly shutting off after it turned on.
The power supply on this model of monitor was not producing a full 12 volts and 5 volts to the inverter board from the video input display board. It was measuring about 11.6 and 4.3 volts. I found that if I put a 4 pole single throw switch on the 4 connector wires that go to the inverter board from the video board I could reset the display once the power button was on after 10 seconds and it would run normally. This is a work around fix until the main reason for the failure is repaired. The real fix is to replace both of the 1,000 mfd 16 volt capacitors in the power supply so it will have a full 12 and 5 volts getting to the inverter board. If it is low on voltage then the microprocessor on the inverter shuts down the display since it isn’t getting enough voltage to run properly. My switch fix was to allow the power supply to charge up without the inverter loading it down. Once the monitor was turned on for 10 seconds then you can turn on that
inverter switch I mounted on the front panel and it would come right on every time and stay running all day. If you turned on the monitor with the inverter switch on then the monitor would flash on and off and stay off but the power LED light would remain green unless the signal to the monitor was lost by shutting down the computer. It was an interesting work around to try out.
Bye for now