Electronics Repair Questions/Answers and Testimonials- Part 75
Your book is realy good, today I fixed my very first slots machine ATA monitor. The whole machine happed to just go off entirely and everytime we switch the machine on it will come on but the monitor will go off again before the machine reach its full operation. Everytime we move the monitor to another machine the problem goes with it. I then took the monitor to the workshop and have a look at it and only to find two swelled small electrolytes situated next to the flyback transformer area, a 10mf and 33mf both at 200v. Replacing those two the monitor came back to a nomal operation. You know Mr Yong today I learn how small components can have a big impact in the system. Sorry my update was just too long, I am just excited.
There is no output at all even with a grounded pin14 and a HDD load. I am an engineer who pursues tesla coiling as a hobby so i am not an expert with smps but i would like to give it a try by atleast identifying the cause though i may not have the smps-specific spare parts.
I have attached the board image with this mail. The pwm regulator is SG6105. The fuse intact and there is no sigh of burnt resistors.
If there is totally no output then this suggest 90% primary side have problem. I suggest that you test all the components in the primary side and check for shorted components in the secondary side, If all check to be good then you need to replace the power regulator and retest.
I recently bought your testing electronic components pdf, and I was wondering if you could answer a question about an older dell lcd im repairing.
Thanks for the support!
It has the blinking power problem, but when I do a voltage test there is zero volts at filter cap and rectifier, I know the board is getting power because of the led lighting up, I guess my voltmeter doesnt refresh quick enough to read the voltage or something, is that right?
Yes by right your meter should show the voltage. I guess the meter may have problem and you need to use another meter to perform the voltage test.
I replaced a bulged cap after the start circuit, could be transistor or mcu? still blinking any advice would be appreciated.
Blinking problem can be caused by few problem. Make sure the power supply output voltages is good and stable-if it is fluctuating suspect either the power supply itself have problem or there is a component (generally is a transistor) shorted in the inverter board. If the power supply has good output voltages then the MCU in the mainboard have problem because the power LED signal is coming from the MCU.
Your ebooks are great by the way,
Selamat sore Mr, saya mau tanya apakah bisa Power supply yang input voltagenya 110v diubah menjadi 220v tanpa memberikan trafo stepdown,terimakasih atas infonya.
Ada sesetengah power supply boleh ubah dan ada yang tak boleh. Sekiranya ia menggunakan satu filter cap dan power FET maka anda boleh cuba guna spec fet yg lebih besar seperti 2sk2645 dan tukar filter cap dari 220uf 200v kepada 220uf 400vdc. Tukar juga bridge rectifier kepada volt yg lebih besar.
I was wondering if you test and repair the main circuit boards also called motherboards?
Motherboard is usually refer to the PC board and the mainboard is refer to the equipment board.
I have subscribed to your newsletter and have found them very interesting and insightful. I plan to purchase your book when I have the money.
Thanks for the support!
I have a motherboard that I have tried to test, and the results are inconclusive. The memory, CPU, Hard Drive, and Power source all tested good, but the computer fails to come on, even to the BIOS.
If you could get this POST card then you will roughly know where to start to troubleshoot PC motherboard. Generally it is difficult to find parts for PC motherboard in the market.
I thank you for the response about ESR i’m comptable with it now and the way you communicate with us my sense you’re really a nice guy.
You are welcome!
I just download your Electronics Repair Article( just in time after looking for parts)
Thanks for the support!
and came across the transformer with the busted internal fuse. I have a power adapter for for my cordless drill charger that the inside fuse was bad and i could not find the exact match on value and size i was planning to replace the transformer after reading your book today, the original power adapter output is 18v 500ma and the replacement i could find is 18v 2000ma is it too much?
The replacement can be used because the amp is higher than the original one.
About my project on motherboard recap its doing good but slow cause i’m still practicing (i have 5 of this dell optiplex280 so i have enough motherboard to practice.. lol )the right way how to removed and solder the new cap since some that needs to replace is to close to the motherboard trace so i have to be very careful not to damage it.
In fact you can apply extra solder to the e-cap pins first and then hold the board in the center, now use your hot gun to heat up the two pins of the e-cap at the right side and at the same time use your left hand to pull out the cap. It will come out very fast. For the small smd caps you may need a rework station which is much faster.
Lastly as what everybody said about you and your book is absolutely true and i still have some of my old books and some books on how to test almost everything electronics but none come close to your books. I hope you won’t get tired of helping and guiding us in the future.
No problem and if you have other question please do email me again.
How are you, hope you are well.
I’m fine thank you.
I am writing to you after a long gap but watch your website regularly. Now i have one question that one ACER monitor 17″ has no data cable and i have to connect new data cable. The problem is only R, G, B is mentioned on the connecting point but others like , h-sync,v-sync,scl,sda etc is not mentioned on the board. My question is how to connect all those points,
You need from the same model to connect the cable.
whether i should try one by one or you can provide any tips.
Sorry i do not have acer monitor in my workshop because different brand and model have different color wire.
I have no schematic of that monitor. If i use try and errror method, will there be any harm to the monitor.
No, it will not hard your monitor except that it will cause no display, sync out and etc.
Please refer to this link for some information about the vga spec:
I have connected the data cable. The wire i have found in the market is having only five wires + one earthing wire, i.e. i can connect only R,G,B and H,V sync. Now the problem is all colors are displaying but color is not proper like sky color is green, green ground color is violet, but white color is normal white. I could not connect SDA and SCL due to very few wires inside. RGB wires are not shield wires. What may be the reason for such type of color. I hope it is due to poor quality cable not due to SCL or SDA. Am i right or not? There is one question that what is the use of SCL and SDA in monitor although i can work with the monitor without connecting those pins also i can use the panel buttons normally.
Yes most probably the wire does not have the ground shielding for the rgb wires. The sda scl is for communication between the computer and the monitor for example shutting down the monitor if it did not use for sometime, to reprogram data in the monitor eeprom or cpu/mcu and etc.
Gdevenin Jestine, I realy appreciate ur montly updates, I hvnt get enough money dats y i hvnt demand 4 any of ur e-book, bt I ve an issue on dis SONY 28inches flat screen-d fault i detected was d horiz transistor bt d 110 voltage was supplin roughly 180V bt I used d 1.6KV mica cap 2 suppress it, it showed nicely bt after lyk 1min I switched it off 2 fell d transistor it was very hot bt nt hot 2 d xtent when there was no 1.6kv cap n also i read d surroundin component wit meter they r intact.so wot do u suggest can be wrong.falety.thanks!
I suggest that you do not modify because it will post some danger to the circuit and user in term of x-radiation. You may need to check the optoisolator circuit (feedback circuit) most probably a resistor that turn into high ohm that had caused the b+ voltage to shoot up.
Thanks for your feedback and consideration really you are doing a good job .
i wanna be a master in this field but dont have any practical knowledge about it hope ..
im from instrumentation field want to troubleshoot some (Drives) AC Servo drives , how ti check the IC?
power supply on circuit board..?
want some personal help from your side will b waiting for your mail.
just suggest me the basic things to b checked.? will b in touch with you.
Checking power supply and circuit board is a big subject because electronics problems are dynamic.
For testing ic we need an oscilloscope. First find out the part number of the IC then look for the datasheet of the ic. Look for the supply voltage (vcc) pin, input and output pin. Make sure the voltage is good and stable when measure the ic on board. If the voltage is good then you need an oscilloscope to check for signal at the output pin. No waveform could be the ic have problem or the surrounding components have problem.
The Microcontroller ic and EEPROM ICs store programs and we can’t test with scope. We can only test the supply voltage and only through replacement we know if it good or bad.
I was given a syncmaster 730mw lcd tv monitor with the blinking on/off light
Opened it up and found that caps 109 ,110 10 volts 1000mfin power supply changed
them and working ok
5 days later it would not work all you would see is the back lights pulseing onoff
Open it up again and checked all caps on power supply all ok
So now I suspect it could be the bit3105 IC HIGH EFFICENCY ZVS CCFL CONTROLLER
I HAVE TRYED TO BUY ONE AND KNOW ONE IN AUSTRALIA HAVE ONE SO IS THEIR
ANOTHER PART NUMBER
Is the output voltages from the power supply good and stable? If it fluctuates then this mean the power supply or the inverter board have a component shorted. If the output voltages is good and stable suspect a bad MCU in the mainboard.
I have a customer CCTV monitor 20”. Problem is display but when i change output transistor its again short. I have changed 3 transistor but all transistor burn. Please tell me which part i will check for slove this problem.
Try check this link:
hi..Jestine.saya ada problem dengan tv sony lcd model:KLV-32S310A.bila switch on lamu depan merah,kemudian tukar menjadi warna orange…skrin tetap gelap.apa kah yg boleh saya kan.untuk pengetahuan encik Jestine.saya sudah mengantikan satu perintang 1ohm1watt(fuse resistor) yg menyebapkan symptom no power..
Biasanya ini adalah masalah cpu. Pastikan cpu terima 5 volt dan check sekitar optoisolator ic kerana sekiranya ada komponen rosak di bahagian ini, signal tidak dapat disalurkan ke power section maka tiada full power akan dikeluarkan dan CPU megeluarkan signal untuk menyalakan LED merah tersebut.
how are you, i hope you are fine, sir i want to know that What is Tripler and what do it in ciircuit and 2nd is what is Ceramic Capacitor what do it in monitor circuit in easy i mean what is Tripler and what is ceramic capactor. plz reply me.
and have you any image of Tripler if you have then plz send me.
thanks & Regards
A Voltage tripler is device used to multiply an alternating current voltage by three and ceramic capacitor function can be found from:
Thank you very much with your e-book.
You are welcome!
For the first time I had repaired a PRIME lcd monitor. It is a 19″ inches wide screen with a model number TW215FHD. It has a symptom of display shutdown after 5 minutes.
I followed your instructions on how to open the cover. Once the cover removed, I scanned all the components in the power supply, inverter board, mainboard and found no sign of bulging capacitors, burnt components. What I did is that I disconnected all the connectors and reseated it back. And then I powered it on. After 5 minutes, WOW! the lcd monitor does not shutdown anymore.
Although the repair is quite simple but you can see the satisfaction in my face when you are successful in repairing. Thanks and hope another lcd for me to be repaired.
Thanks for your useful site!
You are welcome!
I have a Dell E173FPB with the led-blinking symptom. After removing the fuse, the LED wasn’t blinking anymore. I desoldered and tested the 4 C5707 transistors; here were the HFE readings: 30, 357, 371, 445. I replaced the 4 transistors with new ones with HFE around 360 (and kept the two good ones for other repairs). After this and resoldering of the fuse, the led wasn’t blinking anymore, so I tried the card with backlight. It worked for 2 seconds and then start to blink again (LED and backlight), with a slight clicking noise… I tested the transistors again, and two of them had a reading of 0 (shorted?), the other two didn’t change. Obviously there are other faulty components which make the transistors get faulty under backlight load…Probably, if I change again the 2 faulty C5707, there is great chance the new ones will broke again quickly… So my question is: what other bad components can be responsible for that? I don’t have a ring tester to test the inverter transformers, but I have another board from the same model (with a no-power symptom that I didn’t manage to fix), so I have possible good replacement parts (transformers and other transistors for example).
Could you please tell me what you advise me to do?
Thank you very much in advance!
Try check if there is any dry joints in the high voltage transformer and make sure the P-channel FET is not shorted. If possible after the replacement of the 4 new transistors, try compare the resistance between the top and bottom lamp circuit. Any different in resistance value is the clue for you to start troubleshooting on that circuit. Compare the resistance using an analog meter set to X1 ohm.
Hope you enjoyed your holidays!
Yes and it was a good holiday to me and family.
I would like to know a few symptoms of each of these electronic components once they are incapacitated on a board. As these are not covered in your testing electronic components book. This is a very relevant topic for the amateur like me. What would be the manifestation of a
1) Non polarized capacitor or any capacitor, if incapacitated (Damaged) on a circuit board?
Bulge on top or at the side and tiny crack especially in the non polar cap.
If for instance, if a duly functioning amplifier or a TV or any instrument has merely has three bad capacitor out of five (overall number of capacitor in the instrument altogether) and no other electrical component is at fault. How would the instrument manifest itself while operating or what odd behavior would the set or piece indicate on functioning? This question is asked since you have had the great opportunity of mending several instruments and posses extensive experience concerning the same.
It depends on the design and the location of the capacitor of the equipment. If those caps are located in the secondary filter side, the output voltages will be low and this will affect the overall performance of the mainboard. If those caps are located in the supply line of the power ic VCC then it will cause power blink and no power symptom.
2) A coil, when damaged, how would the instrument manifest on operation( when switched on)?
These are symptoms that can be employed to clinch the culprit in the circuit board, especially a novice like me,these information is missed in your book. Kindly shed some light on this topic as your account regarding the subject would immensely assist me. Your response is awaited eagerly.
It depends on where the coil is located. If it is a switch mode transformer primary coil problem the fuse will blow. If the coil is a b+ coil then the power supply will shut down upon turning it on.
I hope you can help me , because the electronic shops cant
I have a battaery charger that I use to charge LIPO and LIFE and NICM and
Lead acid batteries , but I connected it wrong and it poped a SOIC8 eeprom
or IC I am not sure what it is , but I think it is a IC , because it is on
the power supply and is marked on the board as MQ
The number on it is 48359 , I have attached a couple off fhotos to give u an
From the photo the part number seems to be 4835D. If it is 4835D then this is the spec:
and you can purchase the part from the below link:
If the cost of repair is too high then i suggest that you get a new charger from hobbycity.com . Their price is cheap and used to buy RC heli, lipo batteries and battery charger from the website.
i am searching about a circuit that can do as a auto loader for smps power supply . as you know for testing the output voltage of smps and check if the voltage drops under the load you should apply a load to the smps (at the nominal current) and anlyses the result . so i ask if you can provide me by this circuit (this circuit shuld act as a load in the output of smps).
Sorry i do not have such load. Usually i will encourage repair tech to use back the equipment load which is much more accurate. Again it depends on what type of power supply you are repairing-power supply with lots of output or power supply that have one or 2 output.
another thing as you know there are some models of lcd tv in the markets . some of them like SONY- EX710 (edge led ) this tvs called LED but in fact they are lcd. and in the other brand like SAMSONG SERIES 6 – this model known as LED TV so i want to know what the difference between LED TV and edge LED TV .
LED TV placed the LED’s behind the screen but the Edge LED TV has the leds on the side of the screen. Usually the edge LED TV is thinner than LED TV.
I’m so lucky to found this wonderful website. I am asking about troubleshooting and repair ECU of cars. Can you advise me how can I learn to repair ECU .can your book help me. If you have institute to teach me please give me your address
Try visit this link: