Electronic Repair Questions/Answers- Part 51
I am new but I have some electronics back ground.I have a LG 42pc3d plasma the power keeps blinking on and off the led turns green to red. I belive it was a power surge and sometimes the tv will still work ok. I checked most of the components on the primary side they seem to be ok.Now on the secondary side near dc supply for the mainboard that become extremely hot due to a high voltage drop. these are 10 ohm resistors. I starting to get frustrated because I have not fixed it yet trying to locate. the faulty components please help. Thanks
Is all the output voltages stable? Some resistors (wire wound) tends to run hot but will not burnt our hand. If you find that it runs too hot then you may need to check all the components connected to the resistor.
minta maaf jestine kalau tak keberatan jestine nak jawab pertayaan saya, saya ada satu tv rosak saya dah tahu kerosakan dia ialah ic cax2130s tetapi ic ini tiada dalam penang dah tanya merata kedai yang ada cuma ic cxa2139s apa perbezaan antara dua ic ini adakah ia boleh guna atau pun tidak ic ini untuk tv sony atau ada tak dalam simpanan jestine untuk saya beli melalui pos terima kasih
Maaflah, tiada info tentang IC ini. Anda boleh mencuba, sekiranya ia tak berfungsi anda boleh simpan chip in untuk masa depan.
i will order the lcd repair book . i want to know whic book is better to lern how to fix lcd
monitor is it the lcd repair book or the switch mode power supply
If you already know how to test electronic components then go for the LCD Monitor repair ebook. Getting the SMPS repair ebook will make you a pro in solving all kind of smps problem.
i would like to get some tip how to setup analog oscilloscope
you said that the lcd moniter teach step by step i want to know if the lcd moniter will teach me step by step i will send the money by money gram just lik the last time
It will teach step by step showing what kind of waveform expected and etc. Setting up scope is easy.
I have face problem regarding monitor repair i found fly back transformer transistor short (C5301) and FET IRFI9634 short and output chopper 1 ohm resistor. Then I change faulty component. And switch on the monitor again fly back transformer transistor make a smoke then I check fly back transformer after desold. I check inductance of primary and secondary winding according to diagram I found no shortness in transformer. please tell me about yoke coils horizontal and vertical resistance or inductance i check on LCR meter vertical inductance 4.85mH and horizontal 0.09mH I send you circuit diagram of monitor, and also tell me horizontal and vertical switching and signal curve on oscilloscope and how is working monitor power supply details. it means after chopper supply how monitor circuit work etc .may be you not understand what I am saying I excuse for that my wording.
I suggest that you check the internal capacitor:
By the way, it is not accurate to check the flyback and yoke winding with inductance meter, you should use a Blue Ring Tester to check it.
hi, hw do i save a good eprom using ponyprog2000 ? i don’t hw 2 copy & also 2 program using ponyprog2000. i beg u 2 assist me. thnx Trust
You need the programmer and the good eeprom in order to do the job. Plug in the programmer and run the software and select the type of eeprom you are having. select read the eeprom data into your computer, Next put in a blank eeprom and retrieve the good data by selecting write. Press enter and the original data will be written into the blank IC.
Yes i did. Thanks. I want to repair a sahara crt monitor. Please help.
I replaced a rectifier, fuse, voltage regulator ic but still can’t come right.
You may need to check all the components in primary side and also secondary output diodes.
Hi Jestine, Thanks, i followed your advise, resoldered the CTR neck board and alas! My monitor colours are as good as new again. maybe it would have cost me a fortune if i had taken it to have it repaired. your books are helping me along. Thanks again
Thank you, this newsletter about the function of some electronic components in electronic ccts is greatly appreciated because you explained in simple way I can understand the functions. Thanks I am looking forward for the next component function.
Thanks for the March newsletter, I enjoy reading it, very detail and easy understanding,
by reading it, i improved alot of the electronics servicing methode and some function of the components.
How are you doing? I am fine. I have one question for you again.
I got 19″ JTX LCD monitor that has no led light at all. I opened the cover and found two fuses 3A 250V are blown up. I replaced them and still no led lit. It uses external power adapter 12V. Whenever I plug in the adapter pin the led light on the adapter disappears and the fuses get only 0.5V DC instead of 12V. What could be the problem?
Can the DC jack be a problem that causes this? When I check with resistance test it read 14.5 ohms. When I test with analog setting 1X it makes sound. I would appreciate your helps thanks.
It seems like the line of the supply in the lcd have problem. It should not read low ohms when tested both side of the probes. You may need to follow the path to see if the components connected along the line shorted (shorted cap, diode and etc). Usually this supply line may go to different ICs. If one of the ICs shorted then you will get this kind of result thus blowing up the fuse.
HI AGAIN JESTINE
I AM AT A LOSE ON WHAT TO CHECK ON THIS SYNCMASTER 225BW. I CHECK ALL THE CAPACITORS I STILL GET POWER TO THE END OF THE POWER BOARD , BUT SOON AS I PLUG IT INTO THE CONTROL BOARD THE POWER SEEMS TO DISAPPEAR.DO YOU HAVE ANY MORE IDEAS THAT I SHOULD BE CHECKING.I WOULD APPRECIATE ANY HELP THAT YOU CAN GIVE ME.I AM NOT GOING TO GIVE UP UNTIL I FIND THE PROBLEM. THANK YOU AGAIN FOR ALL YOUR SUPPORT.
SORRY TO BOTHER YOU AGAIN
If the power supply is good and all the supply gone after connecting it to the control board then there must be some short circuit in the control board. If there is a short circuit in the control board then you can use your analog meter set to x 1 ohm to trace it. Just place the red probe to ground and the black probe to the control board supply pin and it should not show two readings. If there is two readings then most probably the line already have component shorted that need to be rectified.
Hello , Mr jestineyong it has been long since I communicated to you
otherwise how are things hoping you are very fine on my side I have
been having a problem to solve with a Compaq presario monitor 1525
which when you power on does not work but on checking the power diodes
5404 all of them seem to be dead so I thought of replacing them but
the problem is my electronics suppliers do not have the very diode
what they have is power diode 5408 could it possibly work for me or do
the exact model and please let me know if it is not the diodes only
which have malfunctioned. Thanking you in advance.
I’m fine thank you and you have to get the UF5404 diode and the 1n5404 diode can’t be use to substitute it.
I have one motor control board…. my problem is the tantalum capacitor at the power input before regulator +12V…is alwasy burned when we connect to the load…without load, it can draw 12V voltage….and the capasitor is also in good condition…only after connecting the load, the tantalum capasitor 1uF 35V will start getting hot and burned…. the regulator look ok…did you have an idea what is actly going on there….
the input sequance is like this…
1…input…rectifir diode…electrolytic capasitor….diode….regulator……
the diode always burned…..i check each component using multimeter ad all in normal condition..
Two reasons why a cap can burn. Quality problem and the line voltage is higher than the cap voltage. You need to check the line and make sure it is within spec.
Sir good day to you and to your family and students.
Sir, sorry but i will bother you again this time. I am having problem with our monitors again. some of our monitor no longer display anything in the picture tube. the power indicator is good. when it is connected to the video card is shows that their is a H and V sync happening. Its amber when the computer is off and gree when the computer is on. but the monitor is not displaying anything. sometimes i press the enter key and space bar of the keyboard and after 5 to 10 seconds the display comes out. but other monitors wont come out even i press the enter key and space many times. i found a guide on how to repair this symtom in the net and i did check all the components in according to the guide but all the components are ok. i pull them out 1 by 1……. the only thing i’ve not done yet is the voltage testing.
In order for the high voltage to work you need to make sure there is B+ supply voltage and horizontal drive waveform. Of course the flyback has to be good first. Mising either on the signal above could cause no display symptom.
Thanks again. Just to make sure the DC jack is open, I desoldered and measured the resistance. It seems to work good. I am sure the circuit itself has problem. I check all the filter capacitors with ESR meter and they are in good condition. There is an IC just behind the power jack that is AN7512 same as this link’s http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&WT.z_homepage_link=hp_go_button&KeyWords=an7512&x=27&y=20. Could this be the trouble maker? How do i know if this is a problem? Have you ever dealt with this type of IC? It looks to be robust though. If you
Cheking IC is quite straight forward. First identify the part number, then find out the supply, input and output pin. Next
Once again, thank you for taking the time to answer all of our repair questions. I am sure this is not easy but I do all I can do support you. I have purchased all of your eBooks except the LCD repair book. I am sure I will purchase that one soon enough.
Thanks for the support!
So far I haven’t had a lot of work on LCD monitors but I hope that changes. The problem I am having with this ACER X241W doesn’t sound like a normal break down that occurs with LCD displays. What happens is that every now and then the “No Signal” Warning display will come onto the screen. Most of the time you can unplug the monitor and then plug it in and it will go away, but eventually it won’t go away no matter what you do. When I do a Google search on this problem it seems to be common to many people using this particular Acer X241W. No one has seemed to find an answer or a repair that works. Even thought it looks like many things have been tried. I sent an email to Acer but never got a reply. I fear that this might be one of those problems that might not be able to be repaired, if that is possible. How do I go about finding out if anyone has successfully fixed this problem?
I came across such problem but not in Acer Monitor. It was in Samsung Monitor and the problem was a Bad MCU. There is nothing we can do about it unless we have the programmer.
Dear Jestine ,
Please be informed that we have LakeShore racks installed in our Plant.
These racks include Model 2308-12 rackmount (12 units) power supply module.
During the last year, we experienced 03 failures in one particular power supply module.
The 03 failures show fuse blown, transformer malfunction or power filter capacitor damage on the SMPS module.
The causes of the failures are not identified.
Could you please assist to find-out WHAT CAN BE the reason of these failures. Looks like linked to engineering issue or power sizing.
Well, it can be the components quality problem, design problem, surge problem or even environment problem (too hot, electricity fluctuates and etc).
How can i test this relay in the attachment, i have read you book “testing electronic components” but this relay doesn’t have written comm no nc or coil.
Try use analog meter set to x 100ohm to measure to see which pin have the resistance. The pin that have the resistance is the coil pins. Now pump in 24 vdc to the two pins and you will hear tick sound. Place your ohm meter across the two pins and once you hear the tick sound the ohm meter should register a low reading.
Have a good day!
PLease i need a little assistance from you. there are two LG TVs i am repairing but i cant get the defective parts in all the local electronics spare parts shops available. i have gone to the internet and i seem not to understand the content, and i dont have a data book yet. they are:
i. Voltage regulator – MC33269T
ii. Horizontal transistor – ST2310HI
iii. transistor – D2059
please i need their alternative replacement part numbers.
Sorry, i could only find the D2059 REPLACEMENT which are 2SD1940.
also, if i want to measure b+ voltage to the horizontal driver transformer, should i have a constand DC voltage or is it AC voltage. please help me.
B+ should go to flyback transformer, however some may go to horizontal driver transformer. It should have a constant DC.
meanwhile, i enjoyed the March electronic stuff you sent to me regarding the functions of some electronic components in circuits. it was fantastic indeed. thanks a lot.
You are welcome!
A MONITOR SYSTEMAX MODEL NO J556 BGA IN DEAD CONDITION. ON CHECKING MOST OF COMPUNENTS IN SMPS SECTION AND B+ FET (Q202) PART # IRFS634A WERE BLOWN. ON REPLACEMENT THE FAULTY COMPUNENTS WITH ACTUAL PART #s MONITOR CAME IN POWER ON CONDITION WITH CLICKING SOUND AND POWER LED BLINKING GREEN AND YELLOW. I TRIED TO SOLVE THE PROBLEM BY REMOVING THE B+ FET (Q202), CLKING SOUND WENT AWAY BUT DISPLAY WAS UNFORMED AND OUT FOCUSED. BUT AGAIN CONNECTING THE B+ FET THE MONITOR COMES IN CLICKING SOUND POSITION. B+ FET IS ALSO OK.
Try visit this link:
A small problem. As per the attached drawing it would appear that two double connections on the left are the outputs to the lamps.
The problem is that the LCD lights up for a couple of seconds then goes blank. I would assume that this means that one of the lights is packing up and feedback is shutting the set down.
Yes you are right.
I have tried to determine whether it is the top or bottom lamp. If I put my power meter on the output of the lamp supply will I be able to measure the AC voltage before it shuts down?
No you can’t unless it is totally no AC voltage at all. Some weak lamp can have the full AC in but the weak output from the lamp that cause the feedback circuit to trigger.
I guess substitution with another LCD is the quickest? Many thanks Jestine.
Yes that’s right. The fastest way to confirm the condition of backlight.
i have a tv that was showing a line across i discovered that there were three burnt capacitors i replaced them and everything was ok for a few hours those replacements also burned out what can be the cause of this
Check again all the corresponding components. If possible replace the vertical output IC too.
good morning sir i have face a problem in samsung samtron 45 Bn 15inch monitor
when the power on to the board then it will turn of within one second
i have chech all the capacitors in primary and secondary i was good, and the all mosfet are also good when i checked and as usal diode but there was no power input to flyback transformer( L O T ). sir please tell me hot to check the relay
Try this link:
actually i am going to get one of these insulation tester . that is why i am question from you of course i will be very thank full of you if you tell me which brand is more use full for our job . and with what kind of specifications
I have not tested other brand but mine is kyoritsu and found it to be good. The spec should have the range that can select to 100v, 250v, 500v and 1000v.
Can you please help me with this question?
If you have to put this components : Flyback, HOT, ElectroliticCaps, NonPolarCaps, Resistors, Transistors, Diodes/ZenerDiodes,
Transformers, inductor coils, IC’s
In a list from 1 to 10, from the most and the rare, that are to give problems in CRT TV & monitor circuits, from your experience how would you do the table?
Thanks in Advance
All the components have high changes to get spoilt except the transformer and the coil/inductor which is more reliable.
Hi Mr JestineYong,
I have just subscribe to your Testing Electronic components. I was interested to know how to test IC’s in the simpliest way and that’s how it brought me to your website.
I haven’t really got down to built the IC tester circuit yet. The circuit you presented shows a test for 8 pins IC’s. I was wondering how to test IC’s with more than 8 pins or less? I hope you can assist me on this. I have a Sony player FH-B500K which is faulty and I intent to try to repair it.
To test any ic just find out the part number and the datasheet. locate the supply, input and output pin. Power on the set and make sure the ic is receiving supply voltage. Then check the output with scope. No waveform with supply voltage means the ic have problem. Sometimes it could be corresponding components that make the ic malfunction.
I have this question for you. a acer lcd screen came to my shop with the problem that all picture is green. the customer said that he used it on a mc computer then put it back on pc computer..then the color changed..is that a problem with the eprom? please advice. Thanks
Sorry no idea about this because generally my country use more pc than mac. Try get the customer to put it on the mac computer again. If it is okay then most probably the eeprom or the mcu problem.
Big encouragement on a job well done. Your literature is like treasure to me. I try to learn as much as I can from your posts. I even read your newsletters over and over again and can even memorise some of your articles off by heart.
I’m one of your ERG members that came upon your website with little electronics knowledge about 10% and just from reading your blog posts I’m repairing equipment like a pro. Even some have said that I am a University graduate.
That’s good to hear that.
I have read your articles.
I do have a question that you hopefully will answer. I have three ATX power supplies that have an over voltage condition;
Two are brand new, and both of the three volt rails, are reading 3.67Volts, the other, has an overvoltage condition on the 5V rail.
My question is this; Can the two with the 3.67 volt rails be safely used, or will they blow out the mainboards?
Also, can these conditions be easily fixed?
Thank you fo ryour time and consideration.
Usually an overvoltage supply will cause the e-caps in the mainboard to bulge. There are many causes for this problem. You may need to check the optoisolator area. I came across a bad output inductor (toroidal coil) could also cause the output voltages to increase.
I bought your book about testing electronic components and I have improved
my knowledge in testing electronic components.
I repaired my first fax having power supply problems and now I’m trying to
fix an LCD Monitor (Samsung syncmaster 710V) that has this problem: After
one or two hours working it “becames black” and one floating window appairs,
displaying the message “Not optimum mode. Optimal resolution is 1280 X
I think that the problem stay in VGA Section, but I don’t have idea about
what I have to test.
Can you help me?
Have you ever fixed any similar problems?
Thanks for the support on my ebook. Your problem is a BAD MCU and you need to replace the mainboard or reprogram the MCU. Since i do not have the programmer i would usually buy a new board. This is a common problem in Samsung Monitor.
i have a question;
i am testing a elco cap ( from smps ) 680uf 200V
I tested it with the esr meter.The value is .05.
I can not find this cap on the chart.
How do i must know if de value is correct ?
If you can’t firn the vakue on the chart then you taje the inbetween the chart. For example if 47 uf is 0.1 adn 100uf is 0.15 then 68uf is about 0.12 to 0.13.
Your cap seems to have a good reading.
I have a small PCB board with just two IC’s, zener, diodes, resistors and capacitors.
That problem is that the board does not work when it is cold and after it warms up, it works fine.
Is it possible that the problem are the IC’s? Or do you think it is probably from another thing? Perhaps the zener? What are the electronic components that are more favourable for temperature issues?
Chances is hig on the IC because it is a semiconductor. If after replacement the board still have problem then you may need to replace other components and retest.
Hope u fine in god’s grace.
I’ve got a LG tv today..The problem is the top portion of the screen is blank..bottom portion is working good.
Sanyo LA7840 IC is used here for vertical deflection..
Will replacing this ic fix’s this problem ?? Can u tell me the substution for this IC?
Try check supply (may be a positive and a negative voltage) as one of the supply missing could cause missing one part of the section. If the supply is good then replace the VERTICAL IC.
dear jestine when the tv is on standby i can measure the the collecter of the hot with no problem, but how can i measure it once the tv is on?
You need a high voltage probe to measure the anode voltage which is about 24 kvdc. What is the complaint of this tv?
to see if voltage is lowering down, i want to make voltage testing on the collecter of the horizontal with the tv on thanks
TV hot collector could be always 110vdc and the best point to test is the base of the HOT. Test it with scope. Without this waveform there will be no high voltage but the collector voltage will be still present.
I came across 1 set Toshiba CTV. The problem is dead set.
When I check the B+ line at Flyback pin , the voltage reach 135v but drops the moment TV is switch on.
Even when I open the flyback pin from the B+ line, the voltage at B+ line is still the same result i.e.the voltage reach 135v and drops moment later.
Is it because the HOR Output transistor did not oscillate that create such problem? or problem with the SMPS circuit?
It can be the SMPS or components along the B+ line have problem or the flyback/HOT area have problem. You have to isolate the problem by following the link below:
Quick question – without the schematic, is there a way to determine what value the current sense or startup resistors should be?
It would be hard. Usually the current sense resistor is in the low ohm range from 0.01 to 1 ohm and start up resistors from 10k to 1 meg.
I’ve removed them from the circuit, and the current sense measures 0.5 ohm. Strangely the markings on it are
If you check with normal digital meter you may not get a precise reading because normal digital meter can’t go that low. You need an ESR meter to test the low ohm value.
What I assume to be the startup resistor (it is a high power resistor like the current sense one) measures 243k ohm – the markings are very hard to make out due to heat I think – appear to be red, brown, brown gold, but makes no sense.
If you have confirm that it is a start up resistor then the value has to be higher than the color code above.
With the startup resistor I dont quite understand how it derives it’s voltage – wouldnt it have to be part of a divider network? Or is there a zener in the smps chip that clamps it to the required voltage?
It is sort of like a divider network. The higher the resistance value the lower is the DC voltage.
Have a good day!
Message: hi, i have 7 hp nc6320 tft, some of them got line, some of them got white banner on middle, some of them is full of vertical line. what equipment i need to repair these? normally i am only replace the lcd. u sure this can repair by your guide? thanks
These problems are caused by bad LCD panel and can’t be repaired.
Hi Mr Yong
I want to say something to you ” Thank you very much, thank you for your all repair newsletter, really it’s very useful and monthly increase my repair skills and electronics understanding, then i want to repeat my thanks to you thanks for ever”
have a nice work day
no:1 samsung tv has no raster but green screen
Check and compare the Green circuit with blue and red circuit in CRT board.
no:2 samsung tv have raster but no av (video) mode and went to standby or off after 20- 30mins when hot
Make sure all the e-caps in the power supply have good ESR and no dry joints.
, no:3 trident tv vertical and horizontal problem
Check and replace the horizontal/vertical oscillator IC.
, no:4 panasonic tv have red led but don’t operate that is no raster, no sound and no video mode
Make sure the main power supply power IC is receiving good supply voltage. Sometimes a bad CPU may cause such problem.
no:5 lg tv have raster,video and sound but after 15 mins power on it went to standby mode
Refer to answer 2.
and n:6 gold star tv have raster ,sound and video but sometime picture defective or vertical line in the middle
Check the horizontal yoke coil area for dry joints and bad component.
I am more like getting in this field of Screen Repair as a novice and
my apology if I always asked for help but you are the only one who I
can count on.
My question is this, I have a screen that I try to fix, when I turn
the power on the screen display not steady and it really hard to see
so I try to set is focus and sharp but a problem happened. The
capacitor blown, the big one that located in the power side.
I replace that capacitor with the same capacitor from one screen and
then turn it on. It won’t turn on but burnt the fuse. What is the
problem, am I carelessly solder the positive to negative side on
capacitor, I mean connecting capacitor the wrong way or what?
It could be or there might still components shorted in the power supply. Isolate the problem using this link:
If possible check all components in the power supply before you turn the power supply On again.
I know you don’t repair pc but just thought i would ask incase you could give me an insight where to look next.
Problem started when i was opening up psu to see what condition the caps were in..I closed up the psu and was doing some voltage testing on the psu connector that goes to motherboard ..All voltage rails were fine ..
When i came to restart the pc the fans all spun up but there was nothing on my monitor screen ..This happened a few times but then i was able to get the pc going again .
But for some strange reason when the pc is left on for some time it is fine but if i shut the pc down the problem arises again fans spin but no logo or anything on screen.
If i leave it for a while and then switch the pc on it all works again sometimes .It just seems to happen once i shut the pc off and then try to start it again.
Now i know it’s not the monitor as i have another pc and it is fine ,plus i have 3 spare working monitors..
I decided to reopen the psu and could not see any problems but thought the capacitors could be going so i replaced most of the caps apart from some that were under 10uf ..The voltage rails are all ok but yet still get the same result ,it starts but then won’t come on till it’s been left for a while ..Do you have any thoughts as to what i could do next.
Could i have caused a fault when checking voltage on the connector to mobo ? I know the ram is ok because it’s the same as my other pc ..Was thinking of recapping the mobo incase any caps are high in ESR but not sure ..I do have a ESR meter but i would have to desolder 1 leg of each cap as they are all bunched together.
Any ideas as to why one moment it’s running fine and the next it won’t always start.
Your problem could be cause by the motherboard or the PSU. I suggest that you isolate the problem using another working psu or motherboard. This will cut short your troubleshooting time. The main culprit could be the filter caps (usually 1000uf to 2200uf caps) in psu and bulged caps in mobo. Sometimes having right voltages does not mean it is good because if the voltages rail have problem the voltages may intermittently pull low when there is a load.
Have a good day!
Hi Jestine, I have a Lextron 17″ monitor with the 3/4 of the screen working (top section), 1/4 of the screen blacked out (bottom section). The lamps are working, i conclude it might be the panel that’s faulty.
What you think it could be.
Yes, i have seen this problem before in another brand and the problem is in LCD panel.