Electronics Repair Questions/Answers and Testimonials -Part 67
I have down loaded your SMPS e-book last week via your download page.
I comment you for making your knowledge of repair available to the whole
world. I have been steadily working through the SMPS e-book and the amount of
knowledge and experience is staggering.
You were right, I saw that when turned off the TV they were going out very little sparks from the SMPS transformer pins 2 and 3. So I repaired that dark area with isopropilic alcohol. Then, using my better magnifer, I could see a dry joint just in the IC001 pin 27, the micro´s Vcc. So I repaired it and now all it´s OK.
Thanks a lot, Jestine.
What cause the pull down of voltage in the main filter of capacitor. i have one tv hear sharp. Thre is 220 volts coming but when i measured in the output of ( note this is four pieces of diode that was bridge) rectifier there is a little volts something 3. 8 volts and also in main filter cap 330uf 400v the volt i measure is 3.8 s volts that was the time that i change the ic 1x1791ce.the time that i didnt change the ic i measure only milivolts in DMM. but i already test all the surroundings components and its ok. i also ring the primary and it ring to 8 lights. what might be the problem sir. Thank you sir for the answer in my first email. im only season repairer sir. This tv has two powersupply one that supply the audio and the other main board
I suggest that you check and make sure the bridge is receiving 230 volt ac and then the output of the bridge must have about 300 to 310vdc. Sometimes after the bridge there will be a protection resistor that have open circuit and prevent the voltage from going to the big filter cap.
thank you very much mister ;Yong, I ask if I have to dissmentle all the lcd panel to get the backlights out
Some model you need to dismantle the whole lcd panel to remove the backlight but to some model you can directly pull out the lamp after bending the support at the side. Becareful as removing the backlight could break the cable between the lcd controller board and the lcd panel.
Thank you very much. My husband stay up all night last night downloading and readings the ebooks and didn’t had time to send you this message. He’s very excited and says Very Excellent Stuff.
Will surely recommend other electronic enthusiasts to visit your web site.
Have a wonderful day.
Thank you for your article “How To Repair Dell E151Fpb LCD Monitor Repair- No Display Problem”. I had that model monitor sitting around for a few years and suddenly decided to fix it. I found your article online, bought the FET on eBay, replaced the FET, and like magic, it worked. I knew nothing about monitor repairing and did not do any troubleshooting whatsoever. Just wanted to let you know that I appreciate your generosity in sharing your knowledge. Thanks again.
hi sir, can you pls help me how to check chroma and system i.c.? thank you so much!!
You need oscilloscope to check on the ic. Make sure there is supply voltage going to the ic and then measure the rgb output waveform with scope. You need to download the ic data from the internet before you can know which pins are the outputs.
What diode can i substitute for Z1150 IT IS SECONDARY Output it has a symbol zener diode. It is say transient voltage diode it is between on the two electrolytic cap rated 160 volts. This diode is open that, there is no secondary output. This diode found in sharp tv. Thanks sir.
I have no data on this type of diode but usually i will use UF5404 as a replacement for all secondary output diode.
Another thing i would like to ask is about bridge diode in sharp tv it is four pieces that was form to bridge diode not a package that has 4 pin in power supply area. I test each one with the digital multimeter the 2 pieces has a reading .478 and other two were .465.It has a low output. The diode number T 884-f.
Testing diode with digital meter would not give an accurate result.
Can i use 1n4007 as replacement sir. Thank you again. God bless us all.
I suggest that you use 1N5408 that have higher amp is safer.
I am wondering if a man with your experience can help me. I am looking for a equivalent replacement for a SamHop P-Channel Enhancement Mode Field Effect Transistor. It is a SMD D-Pak part # STU2030pls. I am having a hard time locating this one.
The drain current for the transistor is quite high and I cannot locate any replacement number for you. However, try email this company to see if they have it or not:
HI JESTINE, YES. THE MONITOR HAVE 4 BACKLIGHTS, 2 FOR THE TOP , 2 FOR THE BOTTOM. THEY HAVE ONE IS FULL BRIGHTLY, AND ONE IS DIMMER AT ONLY ONE END OABOUT 3 INCHES LONG,THE REST SEEM NOT LIGHT ,FOR THE BACKLIGHTS ON THE TOP. IT IS THE SAME THING FOR THE BACKLIGTS ON BOTTOM. I HAVE MAKE A TEST. I DESOLDERING THE BALLAST CAPACITOR OF THE BACKLIGHT WHO ARE NOT BRIGHT ALL LONG THE BACKLIGHT, AND THE MONITOR STILL FUNCTIONNIG.AND NEVER SHUTDOWN. I HAVE DO THE TEST WITH 4 EXTERNE BACKLIGHTS. IT IS THE SAME THING . IT IS LIKE IF ONE BACKLIGT TAKE ALL CURRENT AND THE SECOND BACKLIHT HAVE NOT ENOUGH CURRENT FOR LIGHT COMPLETLY .THANK YOU, CHRISTIAN
Could it be the inverter board does not have feedback circuit that can shutdown the inverter? I came across older model of LCD Monitor that will still function even though you have pulled out one of the backlight.
Hi justin, This is nagendra i am testing one cpu smps in that 12
volts supply is not coming, i cheked all mosfet’s and the doides all
that are working properly only thing i findout is 2 Resistors of 200
ohms is become little bit black and it is showing the result above 260
ohms in multimeter instead of 200.
Can u reply me what components to be cheked for this type of problem,
I suspected may 7812 & 7912 reglater IC must shorted but it is not
their in that smps.What may be the Problem ? kindly reply me
If you found that the resistors had turned into darker color and the resistance have changed then you need to check any component that are corresponding to the resistor. It could be bad cap or leaky diode or transistor.
Do any of your books cover using oscilloscope?
Sorry i do not have book that fully cover the scope. You can find many books on scope in amazon.com. Actually, using scope is easy. It depends on whether you want to check ac or dc. If you want to check ac then set to ac and measure the point. From there turn the voltage and time per division knob and expect a waveform. If there is no waveform then you know the circuit or the component have problem.
Tks somuch for leting me no d latest in market, how r u, ur family? Pls sir, i was ask to write a report on computer maintenance & repair in school. How do i write it (start).
My family and I are fine thank you. I used to have a copy of computer maintenance report but i have lost it many years ago. It was given to me by a friend who was in computer maintenance business. Here i found a website where you may need to add some ideas on it to make it different from the website:
hi justine can i replace 200 ohms resistor with 220 ohms becoz i am
not geeting 200 ohms resistor in market, if not tell me the
Connect a 100ohm in series with another 100ohm and you will get 200 ohms.
HELLO MR YONG
please tell me i can use diod 1N 4007 as substitute of 1N4548 first one working voltage
is 1000 v and second one is 100v
From my databook the equivalent number is 1N4148. 1N4007 seems to be too big the spec and the size. 1n4148 can be easily found in any circuit board.
I’m from Bangkok and in the business of LED lighting.
Noted and nice to know you.
Will it possible for you to advise some information of how to test the switching power supply (both enclosed and desktop type) to identify whether is good or poor quality? What kind of equipment or instruments to use?
You need to open up the power supply and see if the design are of high class and if they are using good quality components and circuit board or not. By just testing the voltage (using instrument), we would not know if it a good or poor quality power supply.
i am recieving a monitor tvm .the problem of monitor is no picture .i
was replaced ic lm1269 but problem exist yet and again replaced ic
eeprom 24c08 but the problem exist and donot remedy.the light of tube
without any colour exist then hi voltage worked.please help me
If the high voltage is working then you should check on the heater and the G2 voltage. Heater should have about 6.3 volt and g2 have about 250 to 300vdc.
SORRY TO TROUBLE YOU
I HAVE A BENQ Q7T4 MONITOR AND THE MOSFET IS US
I HAVE A FQU11P06TU P CHANNEL FET CAN I USE IT INSTED OF A FQUIIP06
AS ON THE FET S//C IT IS GKDPE548 SO I THINK I CAN USE THE FQUIIP06TU
WOULD THAT BE RIGHT
Yes you can use it but make sure the surrounding components have no dry joints and no bad e-caps around.
Hi, can i use D2498 power transistor to substitute C5129? I know the order of leads of D2498 as base, collector,emitter. Is it the same order for C5129?
Please,advise and thanks.
No you can’t because D2498 only rate 6 amp but C5129 is rated 10 ampere. You need to try BU2520AF as replacement.
I need some advise. I am checking some SMD Electrolytic capacitors on non working board. I am getting ESR values of anywhere from .89 to 54.0.off the board. My question is, Is checking SMD Electrolytic capacitors the same as checking regular through hole capacitors.
Yes it is the same. For SMD capacitor, the best is to remove it out and test because many designs have smd capacitor connected in parallel that can affect the ESR reading.
The value of these capacitors is 100 uf 25v down to 47uf 16 volts.
I will compare the value to determine if it is good or bad in the same board.
Is there a trick to soldering SMD Electrolytic capacitors correctly. The leads are very short and sit flush with the plastic insulator.
No, a normal solder gun will give problem in removing this kind of cap. Usually i use rework station with the hot air that can speed up process of removing such cap.
Thanks for your mail.well,can you tell me that which model digital multimeter suitable for measure the capacitors.
Thanks & Regards
You need to check with them the model as there are many model in the market. The built in capacitance tester in dmm have very limited range and many caps can’t be tested. If possible get a TES1500 Digital capacitance meter that have more ranges.
If the Monitor display have a white raster. There are few areas i can think off.
First is the CRT board. If the G2 voltage is set too high the display will become too bright. if the G1 voltage is zero it will have the same problem. G1 voltage should have negative 10 to negative 70 vdc. Make sure RGB cathode have about 40 to 60 vdc. If there is no supply to the CRT board then it will have bright display.
If the above are tested good then direct replace the vertical output ic as in some cases a bad vertical output ic also could cause display bright problem with some color patches.
Thanks for the many inspirational electronics repairs news and tips and articles you send to me always. I ‘ve always thought of going into full time electronics repair and now I’ve got the avenue to do just that. I ‘ve also considered buying one of your e.books though the money is not yet available. More blessings for you. Many thanks. Sir we have an LG TV set that draws a single horizontal line on the screen and trips off and on intermittently. We have tried the vertical Ic ok, the base cap ok, the yoke ok etc. We are at our wits ends. What could it be? Thanks.. Nwankwo.
Have you check the supply supply voltage to the vertical ic? Have you check all the components surrounding in the vertical IC? Sometimes a bad h/v oscillator ic also could cause this kind of problem.
please i am having a problem with a 21 inch sonny tv. it came in with a no power symptom. i found the HOT shorted. on replacing it, the set came back to life and worked well. however, it was returned two days later for the same problem. i laso found the HOT shorted again this time.
i have tested semiconductors and other components around the horizontal circuirt and there is no sign of defect when i scanned through the board. please i need an adivce so that i dont replace the HOT and it is thereafter returned again. the part number of the HOT is D1878.
Try check from this link:
thanks jestine for your reply.i just need to wait for a few days before i can send my payment bcoz my place is too far to the city and our sked going to the city is once a month only.does it possible to order the books one at a time?so to say one book every month?
Yes you can order one at a time.
about my question regarding the tv im repairing,i dont have special tools like oscilloscope and i just rely on component and voltage checking using my DMM. to be honest mr.yong,my real concern is to learn how to use the oscilloscope in troubleshooting effectively,
It is not difficult to use scope. As long as you know that the point that you are going to test have waveform then expect waveform to be appeared in the scope screen. No waveform means have problem.
secondly to learn to reprogram the EEPROM ic.
You need a programmer to program an EEPROM ic.
i havent came across this topic in your concern.if this is available please let me know.lets go back to the tv im repairing,there is no voltage on pins 2,33,34,35 and pin 36 of system control ic LC863532C but if i desolder(disconnect) this pins ,5 volts will be present on their assigned terminals.is there an open or short within the ic itself?
If you disconnected the pins and the 5 volt appears then the cpu can be shorted. Sometimes the source of supply (5 volt) can be the fault too because it can’t maintain the current draw from the cpu
with regards to the memory ic 24C08 their pin voltages are:pin 5 and 6-4.5v,pin 8-5.1v pin 1,2,3,4,7 are connected to ground.there was a raster at first then suddenly turn to no high voltage symptom.i have checked ALMOST all the components and i havent found faulty parts.i hope even without scope(for now) with your expertise you can give advice on what went wrong to this circuit.THANKS A LOT AND MORE POWER TO YOU!!!
You need to check the B+ voltage because if it is too high it can cause high voltage shutdown.
I want to replace the capasitor for my lcd monitor power supply, but the electronic shop that i went to buy the componen have out of stock for capasitor 220uF 25V. They only have a 220uF 35V.
so my question is, Can i replace the capasitor 220uF 25V (original) with 220uF 35V? and what is the consequence if i do that?
Thanks in advance for your help
Yes you can replace the capacitor with higher voltage and there is no problem with it except it could be slightly more expensive.
a friend of mine ask my help regarding with his Samsung Syncmaster LCD monitor. He said he can see the display but its very dim. I think the backlights are dead. Have encounter this kind of lcd problem? is it possible to replace the backlights?
It can be dry joints in the high voltage transformer or one of the back light have problem that shutdown the display. You need to check if the inverter is getting supply or not.
or is there any other way to make the backlight work again?
If the backlight have problem you need to replace it with a new one or salvage from a junk monitor.
I already check the powerboard and i did not find any bulky capacitor in it?
If there is a pico fuse, make sure it is okay.
Just to share with you that the Daewoo LCD TV Model: DSL-20D1T is working again J
I have managed to dismantle the Transformer T31 and fix the broken coil !!
All voltages are then tested within specification.
Have a great day
Hi Jestine, i’m still learning the books i purchased previously and i’d like to applaud you for helping me get back on track with electronics. If it were not you i’d have not known a lot of troubleshooting methods.
You are welcome!
I’d ask a favour from you to briefly help me with testing flouriscent lights,
Since flurosecent light is cheap and is easily available from any house thus we just swap it to confirm if it is good or bad. Normal meter can’t test it since inside is filled with gas.
components layout and to troubleshooting tips. I’d appreciate your help. Enjoy your day.
Have a good day!
Hello Jestine hope you are in a fine shape.
I’m fine thank you.
I’d like to thank you for having such a great website thus I really learned a lot about electronic repair specially monitor repair.
You are welcome!
I like to ask your help if you don’t mind about this AOC 17″ CRT monitor model 7En with a wide width problem w/c cannot be adjusted thru OSD menu. I’ve replaced the TIP122 transistor and ecaps surrounding flyback section and the problem still there, do you have any other idea how to solve it.
Have you check the modulation diode for short circuit? Sometimes a bad eeprom data could cause this symptom too. Make sure the TIP122 transistor have voltage in the center pin.
Also I have this JVC 21″ color tv with blurred picture at power on and slowly go to normal at warm up. I’ve checked G2 and it’s slowly increasing from 240V- 370V until the picture goes to normal, B+ is 116V. Is it a bad fbt. Pls advise.
Yes, the flyback divider already have problem.
Thank you for the article sent to me. However, I have a DC HV capacitor that explodes when energized. I do not have a replacememt. Is this capacitor bad? It is neither short nor open when tested.
When you said exploded then it is bad. The value can be out. Look for the casing to see if there is any crack.
Nice to meet u again. Anyway just want to ask u somebody just bring in the 29” samsung TV.
The problem is that HORIZONTAL TRANSISTOTR D5703 always overheat and shoted. After change the new transistot, the power will on a few second then blink gradually power goes off and output transistor burnt. During start up period the flyback make klik noise. Hope u could give me the answer soon coz my customer want thier TV urgently. Thanks.
Please visit this link: