Electronics Repair Questions/Answers and Testimonials -Part 65
My Instructor you a man of action you are the solution to many
Be informed that i am enjoying your fifh ebook and it is very wonderful due to the contain in it. Thank you very much for such material, it is lovely.
Your new book on Electronic repairs articles is a wonderful asset!!!!
Thanks a lot for having shared your knowledge with everyone.Very few people will be willing & ready to teach others what they know & again i say thank you.For a long time I’ve admired to know how to repair & test circuits but a wasn’t able due to a few problems here & there but i do believe that one day if i get the finances i will enroll in an Electronics class.Thanks for everything you have done. Enjoy your evening
Hi pal, thanks alot for educating us in the simplest and most understandable style, hence making electronics look uncomplicated. After ensuring that i know the work of each zone in the SMPS i realised that one of the sart up resistors (120K) had blown and on replacing with 100K(available), the problem was solved. Keep it up mr.Jestronics.
hi jestine ,
this is saiprasad koli
how r u
today i am very very thankful to u,
whatever knoledege i gained from u within a days ,i found 100% result from the books i am working in
i do all electronic job from the hospital
one nurse from the hospital gave me tv for repairing
i open the tv and find the resistors burn in abl line ,
one month passed ,still i was not able to find the value of burnt resistors,
but then i thought why cant i try to find from burnt resistor ebook
so i read this book and within a day i got the values of resistor ,i fixed it and it was like a magic
now tv is in working condition and i also used the bulb trick method to it
now i am satisfied and very much thankful to u
thanks sir,,,for the news letter this month,,,,as of now im still reading your books and absorb more knowledge from you,,,i really appreciate your books sir,its a very nice book,,now i really amazed the secrets of smps,,,,a big thnks for you sir,,,,im really want to buy your esr meter,but as of now i save money for tester sir,,,god bless,,,
i have a grundig 20″ ctv having CUC132 pcb. Before a month ago i found that my tv is not start. means no sound and no picture appear. So I called a mechanic to repair it and he tested it and changed the EHT and a power switching transistor of rating BU508DF. And after that my tv is started on. after 5 days next my TV is suddenly going off as i seen the condition before. sir i am engineering student. So I tried to repair it and open it and test the BU508DF transistor and i found that the transistor is faulty so i replace it by new one and my is is started and run. But after 2 days my TV is again suddenly turn off as happened before so again i replace the transistor and my TV again going off after running number of hour. So i can’t decide what I should. So sirs please give me some advice.
Sir .i wills still wetting to your advice.
Please visit this link:
i am working in a media office as a service engineer for the last 10 monthsone old PC was not responding in terms of power on. i just got your site through search engine,rad article on SMPS & applid the trick of cleaning the fan by ele. spray. it is working without any problem for the last 4 days.
thank you for the tip.
I just repaired my LCD and it turned out that the bulbs were ok. I borrowed 2 bulbs and attached it to the inverter board and it showed that the lower bulb didnt light up when I turned on the monitor. So exchange the ICs on the inverter board but still the lower bulb didn’t light so the next step that I swap was the ballast capacitor (3KV) that was connected to the high voltage transformer on the inverter board, then when I test it the upper bulb didn’t light so I replaced the ballast capacitor with a new one and now my monitor is OK. All 3 monitors the problem was the ballast capacitor.
I was lucky to have borrowed 2 working bulbs.
And thanks to your tips for troubleshooting LCD screens.
Thank u sir for thar ebook ..But in
Please visit this link:
http://www.repairfaq.org/REPAIR/ as i found it to be very good.
Sir where can i get softcopy or hardcopy of computer circuits like smps , UPS, …
Sorry no info on this but you can try to search from this link:
Hai Justine apakah yang menyebabkan TV hanya dapat satu siaran saja?Kalau dah dapat siaran RTM 1 siaran TV lain langsung tak dapat walaupun telah di adjust beberapa kali secara auto ataupun manual di bahagian tuner tu?
Harap awak dapat berikan sedikit tips..
Kemungkinan masalah Tuner ataupun EEPROM data sudah rosak. Pastikan semua voltan dari power supply adalah baik.
Hi yong;I have one more question what is the diffenence between Tintaluim cap and ordenery cap?i saw one power supply when i replace inplace of tintaluim diffent type of cap its behave different.
what yours experience?
Tantalum Capacitors are electrolytic capacitors that is use a material called tantalum for the electrodes. Also, tantalum capacitors are superior to aluminum electrolytic capacitors in temperature and frequency characteristics. Please do not replace Tantalum cap with ordinary cap because ordinary cap do not have high stability in term of tempareature and frequency.
Hello sir, i just want to ask your help regarding my problem in
solving the trouble of my television. The display color seems like
fading . My TV model was Sony KV-DA29M81, I’m trying to adjust voltage
across the bias voltage of the color but suddenly no trimmer were
installed on the board or circuit. The voltages for the following colors
red drive – 2.9 volts
blue drive – 2.7 volts
green drive – 4.2 volts
these are the action I’ve done on the Tv
– check filters caps across CRT board – no leaky caps seen
– check filter caps along fly back – no leaky caps seen
– resolder terminals – still
Do you have our previous email conversation? There can be three problems, weak picture tube, bad components in the color section and eeprom data had corrupted. From your description, most probably the EEPROM data had corrupted and this need to be programmed again but you may need the exact EEPROM data.
I have a problem. My LCd monitor was cracked and the display was garbage.
Can i replace just the broken part of the screen with the same size of monitor screen?
Thanks in advance,
You need to replace with the same LCD panel because different LCD panel have different socket.
hello sir, we need to help about my LCD 17″ monitor brand acer model FP555 their problem is rainbow display i can’t not to solve this problem?
Rainbow display can be the problem of bad LCD panel or loose connection in the cable between the mainboard and the lcd panel.
hi sory to email you could you please help i have a panasonic TH50 PX8B and it has a black line down the center of the screen i have read a few forums which says it my be a resister on the ribbon were the line is but there is no resistors on the ribbon so would they be on the C1 OR C2 boards that the ribbons are atached to any help at all would be very help full thanks dave
Since there was resistor on the cable then it could be the board or the panel have problem. In this case you many need a good plasma tv for comparison.
Thank you very much for your confirmation of my subscribtion and I read through your free report “How To Be A Successful Electronics Repairer” the wonderful interview with Steve French and assiciates. its really encouraging and inspired me to return to my repairing job which i struggled through for more than 30 years and ended in 2005 May due to an unfaithful partnerships relation. Most of my technical experiences are digital.
I’m almost 60 yrs now and planning to start doing repair again after layoff for more than 5 years. My experience with faulty pcs and monitors are mostly caused by bad and leaky caps. I couldn’t find any ESR capacitor tester for sale here in Kota Kinabalu,
Again Thank you Jestine for you web site with so many information and would keep me busy for a couple of days.
Bestwishes and regards
i have a problem with the replacement of stpr320 ultrafast diode..
ihave no ecg replacement book.. i want to buy it.. but there is no ebook of that ecg..
cant u plz help me with the replacement of that diode?
thnk u very muc
Try the normal Axial lead UF5404 or FUF5404 Ultra fast recovery diode.
1. Saya sedang membaiki CRT Monitor, masalahnya Horizontal dia tak boleh di adjust.Screen dia memanjang kiri dan juga kanan.Bila kita switch on komputer tulisan yang selalu keluar sewaktu boot komputer terlalu kekiri.Bahagian adust boleh adjust sikit saya.Boleh tak saudara Jestine berikan tips di bahagian mana harus saya check lagi.
Kemungkinan modulation diode ataupun pin cushion transistor dah rosak. Kadang kala data dalam EEPROM pun boleh corrupt.
2.Saya juga membaiki TV made in china 25″.Masalahnya no display dan bila saya troubleshoot saya dapati HOT dia dah rosak so saya replaced dengan yang baru.Bila saya switch on, TV kembali berfungsi dan gambar pun sudah ada tapi selepas 20 minit display terus hilang.Bila saya check semula saya dapati HOT sudah rosak semula dan heatsink menjadi terlalu panas.Apakah yang telah menyebabkab HOT rosak semula?
Sila masuk laman web ini:
First: what kind of voltage i have to read? D.C. or A.C from the flybackt?
It depends on which pin you are measuring. If it is B+ then DC. If other pins is AC but all these are high pulse AC thus your normal ac voltmeter can’t measure it. If the pin pass through a diode then you can expect a dc voltage.
I am reading 101 V D.C. from the flyback. Is this the B+ voltage ?
Yes is about that as some have 110 vdc.
I am reading – 2V at the base of the HOT.
Is there any trhing wrond that i do.
Please a answer?
This signal can only be measured by using an oscilloscope. This is how a base waveform look like:
I’m presently residing in
Thanks for your reply.
Most of the electronic appliances nowadays used 50/60 hertz. However to some manufacturers may may stick only to one frequency which is either 50 or 60 hz. Some 60 Hz appliances will work fine but others with simple motors will run too slow on the lower frequency of 50 Hz. Similarly, some 50 Hz appliances will work fine but others with simple motors will run too fast on the higher frequency of 60 Hz. I guess you should try it out and to see the result.
Hi Jestine, my name is Hector Munoz, I am enrolled in the electronics and computer technology program at Devry university, this is my second year attending to classes.
Noted and nice to know you.
I have a little problem with a sony audio/video control center model No.STR D665 AC 120V 60Hz 186W. When I turn it on the PROTECT mode displays after two seconds. How can I troubleshoot this problem or how can I get rid of it?
The unit may have an overload caused by a short circuit, internally or externally. Try disconnecting all the speakers, then turning up the volume. If nothing happens, connect one speaker at a time and turn up the volume to see if you get more sound. One of the speaker may has shorted internally and this will help you discover the bad one. However, if when you have all the speakers disconnected, and the unit still goes into protection mode with the volume up, then there is a problem with the unit itself. Try check if the power supply supply is producing good and stable voltage or not.
Thank you very much for your time I will appreciate your help.
You are welcome.
By the way I bought one of your books and I will get more soon, they are amazing.
Thanks for the support!
Yes I have a digital capacitance meter.
Is there any code for such capacitors and the code for varistor on the bodies?
If I use my digital meter to read the two, what is the value for a Varistor in a good condition?
I have seen so many of the capacitors resembling a varistoe and this type of capacitors, what are called and can they be used in where as a form of over voltage protection like a varistor?
Varistor comes in many different types of code but capacitor code is usually rated as 222, 331, 473, 271, 152 and etc. These capacitors cannot be used as protection like Varistor.
May i know how to check on the rechargeble battery as attached.
I can use the multimeter to check on the voltage when it is full charged. but, i unable to detect it and make sure it is in a good condition when it is at low voltage.
You can use any voltage meter to test the battery. red probe to the red lead andblack probe to black lead. You should get about 13.8 vdc for a good battery. If you get lower than that, the battery may need to be recharged or replaced with a new one.
Hi Sir Jestine,
Thank you very much for the reply. The electrolytic capacitor I’m referring was the filter cap of a switch hub power supply I’m repairing. Though 680uf 10 volt is not available in our electronic store, I replaced it with 1,000uf 10 volt cap. Now the hub back to work again. Thank you and god bless…
I’m planning to purchase an oscilloscope, as i’m new in the field of repairing i need some advice on what should i be looking for in an oscillscope (bandwidth,channels) i’m planing to use them to troubleshoot Lcd monitor & tv’s i’m just doing this as a part timer, please advice on price range i should expect and also if possible where i can get them from(New/Used).
You need an analog or digital scope with at least 100Mhz 2 CHANNELS so that you don’t need to upgrade again in the future. I’m not sure about this price range, i guess you need to check from local yellow pages to find shop that sells scope. There is a company by the name of Vanguard that sell lots of test equipment
You may also buy from ebay but you need to pay for the shipment. Recently i went to pasar road and saw a new scope of 20 Mhz which cost about RM2500.00. If you have the budget you can buy new scope otherwise go for a second one.
Good day. I have opened up this Samsung tv now. but to be honest i can hardly see the components because of dust. i need to clean this thing out but i see a warning sign which says, ” To determine the presence of high voltage arc or meter second anode lead to chassis only”
What does all this means, i dont want to go poking in and dont know exactly what to do.
This mean that you need to discharge the high voltage at the anode if you want to service or repair the set.
The Tv gives a rainfall sound but no picture. You did advice me to check the voltage at the ctr board, but could all this dirt cause ‘No picture’ condition that now exists.
Dirt would not cause this problem but the dirt could prevent you to locate dry joints, burnt component s and etc.
What voltage should i expect at the ctr board which seems to have gone through some high temperatures. Thanks
G2 should be 250 to 300 vdc. RGB should be 40 to 80 vdc (depends on model) and heater (you can’t test this voltage because it is a high pulse ac voltage from flyback).
If the flyback did not energize then make sure the B+ voltage have about 110 vdc and the HOT base have signal from the horizontal oscilllator ic and you need to test this base signal with a scope.
I hope you are doing well.
I’m fine thank you.
My repair business is not too good but I still open it as a additional income, mainly because people would think the repair fee above 45 MYR for LCD monitor is too high, and they prefer to buy a new one, so at the moment the repair is mainly dealing with CRT monitor with 28 MYR repair fee. How do you think about these repair fee, are they too low compared with your country?
I’m charging RM55.00 for CRT (14 AND 15″) and RM75 for 17″ CRT. LCD Monitor 15 to 17″ is RM80. 19″ and 21″ is RM150.00
The fees is depends on the competition and the quality of repair.
This monitor comes with the problem B+ coil near flyback is too hot and had its outer plastic package melted ( see the photo ), but I had checked with the Blue Ring tester found to be OK. So far I have checked the HOT and surrounding diodes & e-caps are normal.
I dare not to do the voltage test because though the led indicator are glowing steady, there is no display at all, and I’m afraid turning it on a little longer would burn the B+Coil. What is causing the B+ coil to be so hot? I never come across this kind of problem before.
A too high b+ VOLTAGE, quality material used and corresponding components have effect on the B+ coil. If you get the right B+ voltage and the coil still get hot then i suggest that you rewind or install with a new coil.
The problem of this monitor is the screen voltage gradually increasing with warm-up ( the raster would become brighter ) but the focus is still fine ( doesn’t turn blur ). In this case where could be the problem, inside the flyback or defective component outside the flyback?
Remove the G2 wire and measure it.If the voltage slowly increase then suspect a bad flyback otherwise suspect a bad tube or components related to the G2 line. In your case, most probably 90% is the flyback problem.
thanx a lot. I think th ic is gone but th isue is for me to find a replacement part any advice. th part number is LM 13700d and all my stores don’t sim to have it. although I managd to find th 5532d by 2 for each chanell respectively . but I think thy are subject to th main ice the LM13700d. please help if posible. thanx in advace.
Try this link:
I am trying to repair a unit.
It has a 3.3MFD250V 20% Cap in it
I have a 4.7MFD250V and a 2.2MFD/250V Cap.
Can either be used although they are out of the 20% range?
Also, I just downloaded your new ebook but have not gotten a chance to look at it. Thanks for all the advise and help so far and looking forward to reading lots more in this new one
You can try out the 4.7uf 250 volt. If the cap is in frequency circuit then you need to get the exact value otherwise you can use a slightly larger cap but not the lower one.
I’m Jason, and I really like your article which you have submitted at ezine articles.com.
Can you help me with my LCD monitor problem?.. I have attached a picture for you to look at the problem. It seems that my fuse was toasted. I’m not bit of a tech guy or something but I want to repair this on my own. I have checked all the capacitors and it seems they are all ok.
From the photo it seems that many electrolytic capacitor have bulged and you need to replace it.
What are the possible causes in order for the fuse to get burned like that?
Which fuse you are referring to? The main fuse or the inverter fuse? If fuse blow that means that is already a short circuit in the component. Sometimes a fuse may burn by itself due to lifespan and quality.
At first, I thought that it was only the backlight or the cold cathode light that illuminates the LCD cause it has still power and the green light is on everytime I put on the PC and when I flash a flash light on the monitor screen I can still see images on the screen. I hope that you can help me diagnose and narrow things down to solve my problem.
Thanks much and more power to your school!
Now i presume the fuse is the inverter fuse because you can get to see a faint image. Just direct replace all the bulged cap and clean the board and retest.
Hello sir jestine good evening hope your fine, sir can you help me i have 2 AOC crt monitor this AOC is semi flat the problem is if i turn on the display is white the second monitor the problem is if i turn on all the LED is green then no display. hope you give me and idea and possible couse. thanks sir Good Luck………. God Bless
White picture could be the problem in the CRT board. Make sure the G1 pin have negative voltage from -10 to -70vdc. G2 voltage not too high and it should be around 250 to 300vdc. Make sure the crt driver ic or the transistors is getting about 70 to 80 vdc.
Second unit with green LED but no display-does it have high voltage? If no then you need to check on the B+ voltage to flyback and make sure the base of the HOT receive a squarewave.
I purchased your book testing electronic componets
Thanks for the support!
..i wanted to get the SMPS guide since that is what im working on..but i thought i better crawl first.
Yes, one need to be able to test electronic components first before moving to second level.
So far its a good read..alot of information. I jus have to re-read and take notes so that i have a refrence to go by.
I am really shocked that you so much is done with an analog tester and that it cant be done on a digital meter..
Analog meter is much precise in testing the diodes and transistors.
I do have a question…What type of Sodering gun and soder plunger do you use?
For the soldering gun, I’m using hakko 981 presto. For the desoldering pump i use hakko pump. For the lead i use 60/40 lead which means 60% thin and 40% lead.
I have a soder gun i purchased from Raido Shack but it takes a while for it to melt the soder, and the exposure time the componets are subjected to may cause harm to them.
That’s why i prefer the Hakko that have dual modes.
I also have a analog meter but it only goes up to x1k I see yours goes to x10x . Since x1k is the higest ohms setting i have can i still perform the test the way you show them. For example with a 4 leg Bridge Rectifier, your test to show it is good is to take the positive terminal to the first leg and the negative to the second..haveing you meter set to x10k. There should be a reading… now reverse the legs and touch the black to the first leg and the red to second..it should not have a reading.
From my experience, the x10 k ohm is much better than the x1 k ohm because it can output 12 volt from the test probes compare to the x1 k which could only output 3 volt. Testing a semiconductor with the 12 volt output is much accurate than testing it using 3 volt.
I have some question.
In your SMPSbook your talking about “LOAD” on page 137.
What do you mean by LOAD.
What is a Stand Alone type SMPS.
Have a nice weekend
Yes, thanks and i have withdrawn the money. Load means the motheboard. Stand alone power supply means a power supply that have nothing connected to it. Which also means no board is connected.
Hi Yong.I have one more question
i repair some power supply,its used opto isolator which is three pins on side total six pins how we can test its good or not?
If you check the spec you will find that pin 1 and 2 is a LED diode and you can test this diode using analog meter and it should have one reading. Pin 4,5 and 6 is a NPN transistor and you can follow my ebook in the transistor topic to test it.
We experienced a black out in our city. When the power suddenly came in and out a few times within a few seconds, I saw sparkles shooting up from the back of our tv with a CRT. The first time, the sparkles was red. The second time seemed to be blue. There was burnt smell. Although it still gives out picture, the color changed from all colors to a single gray color which I would still watch. The picture takes over ten minutes to appear after the power have been turned on with a noise like tac tac tac for a while.
My questions are: Any safety concern about the tv? Would the high voltage crack the glass CRT? Would there be any radiation leaking?
It won’t destroy the TV tube otherwise you will not be able to see the color or the display. It was the CRT board components that burnt and you need to troubleshoot it. If you have no experience then i suggest that you end it to the tv repair shop for repair.
i have syncmaster 172s tft problem is that when i power on it show white screen and very thin horizontal red line after sometimes it become normal automatically can u help me in solving problem and how should i open this model
Make sure the output voltages from the smps are good and no bad or bulged filter cap. check for loose connection in the cable between the mainboard and the lcd panel. If everything tested ok then replace the lcd panel.
Hi Mr Yong
Thanks for all the news-letters that you have been sending me,they really helps me a lot.
I have a problem with an LG TV,it switches on but the problem is with the screen it doesn’t display but i get 120Vdc between Vbe on line transistor.I took out an IC:TDA6107Q which is at the back of CRT and the TV is still not showing anything.What might be the problem?
I suspect these IC,but I’m not sure.
The first thing you must check if the base of HOT receive any squarewave from the horizontal oscillator ic or not. You need to test it with scope. Since you said you are getting 120volt at the HOT thus the B+ voltage should be no problem. Without the base signal HOT will not switch thus there will be no high voltage. If no high voltage that means there will be no display.
Just a quick story. I’ve read your eBooks and have learned so much. The board on my refrigerator cause my ice maker and freezer to quit working. The repair man said it could fix it for $200US. My wife wanted me to get him to fix it but I said no. I pulled the board out, 4 screws, and used my e-cap tester I got from you. 2 of them tested bad. After a trip to the Radio Shack to get two new caps, I installed them and everything is working great. You saved me $200US. Thanks again for sharing your knowledge.
Hello Jestine, I was working on a power supply today and came across a 17P06 P-channel mosfet that to me tested a little funny.
My question is would I test it in the same way I would test an N-channel ?
Yes, using the same way except that now you reverse your probes.
Or would you test them like an npn and pnp transistor?
You need to follow back the fet testing.
Sir, I did buy one of your e-book. I have a question, in a PC power supply, can I change or swap the main capacitor which is 330uf 200v to 470uf 200v or 680uf 200v.?
Yes you may replace it with 470uf but not 680uf because if for long run the capacity in 680uf will be lose out faster.
i have sony 19 inch monitor colour fault, l think LM2402t is fault but not available today market,sir how to rectify this fault please help me
Try buy from this link:
http://www.utsource.net/LM2402_2.html without this IC you can’t make it to work.
Good evening sir, I’m repairing AIWA TV model # TV-C148SH without OSD. I’m just wandering if you could tell me where could be the possible trouble of this TV. Thank You Very Much Sir.
No OSD could be the problem with the CPU, CPU crystal, EEprom data corrupted and the supply voltage is not accurate to the IC. make sure also no dry joints in these area.
So, I have two questions about the ESR results and the chart:
1) If I test a 47µF 35v e-cap (which is supposed to have a 1 ohm ESR reading, based on the ESR chart) and get a 0.5 or 0.2 reading. Is it a good or bad e-cap?
This is a good cap
2) If I test a 47µF 35v e-cap (which is supposed to have a 1 ohm ESR reading, based on the ESR chart) and get a 1.5 or 2 reading. Is it a good or bad e-cap?
This is a bad cap and sometimes it depends also on which circuit you found the cap. My rule of thumb is i will replace the cap even though if the machine is still running with these caps because i don’t want the customer complaint after few months of using the machine.
Thanks for helping me to better understand ESR results.
You are welcome!
i am repairing an lcd monitor and got stuck on mosftet ic with 4 pins oddly marked 4525geh ? any ideas where i can locate data sheet
Try this link:
Thank you for the information this was very helpful to me I did the same as what was in the Photo and the power supply worked then cut out I did track the fault down using your web site it turned out to be the processors fan that was cutting out.
Good to hear that!
The odd thing was the fan give no indication at first as the power supply was cutting out I got thinking of bulging Caps in the power supply was the problem then in front of my eyes the processors fan stopped dead and the power cut out.
I checked the processors fan and found it has resisterance by using my finger and pushing the fan rotors it would not spring well so viewing your page here solved the problem: http://www.electronicrepairguide.com/Atx-Power-Supply.html I am really happy I got to the problem so quick.
Its your hardwork and your passion that drive you to success.
I was looking at buying a new power supply and came across Power supply Testers this is the first time I have seen them and think how many more people have not heard of them.
They seem to be an excellent devise for any one to test there computer power supply to see if it is the power supply that is at fault or some thing else here is the two devises I have order my self on ebay: http://cgi.ebay.co.uk/ATX-SATA-Power-Supply-Tester-W-LCD-Display-20pin-24pin-/250551881473?pt=UK_Computing_PowerSupplies_EH&hash=item3a560e4f01 also http://cgi.ebay.co.uk/ATX-20-24-PIN-SATA-FLOPPY-HDD-POWER-SUPPLY-TESTER-NEW-/160393750321?pt=UK_Computing_PowerSupplies_EH&hash=item2558366731
I don’t know do you think your members in your news letter would like to know about the devises this would speed the fault finding up and allow a beginner to check there power supply..
Thanks for the link and yes i did posted it before in my blog 2 years ago. Sometimes, in this kind of repair line we need such a tester like that.
Thank you very much for the Repair Article of October 2010. I did not know there were so many different types of Optoisolator IC’s. Thanks. As I have mention to you before, I’ll be among the first to read your fith ebook and did. It covers many intresting topics that required more study time.
I know what is the problem. After much searching online, I managed to find the service manual. Apparently, the guy who sold me this faulty LCD tried to repair it as I can see some components soldering is fresh. He replaced a thermistor SCK-103 with a capacitor of value 103 which I asked you earlier. I managed to get an exact replacement SCK-103 thermistor locally and it works!
Thanks to your ebook “Testing Electronics Components”, it made my troubleshooting faster.
would you please advice me what would i have to check when i have a tv set taking too long to start up , it’s start up the sound first then after nearly 10 miutes or more the picture start to appear either. thanks
Check that the G2 voltage at the crt board is good. A weak CRT tube also could cause it to take sometime for the display to appear. Make sure also the heater voltage from the flyback is properly connected to the crt tube.
Meanwhile I have problem with switch mode power Transformer. There is
no mention of how to test the secondary coils since there are five leads to
this transformer I am bewildered as to how to check the continuity of these
five terminals. There is no mention about this subject as to how to test
these leads in the Testing Electronic components book. Although I have
isolated the cause as the primary coils failed to indicate the continuity.
Before I buy from a electronic shop this transformer, would like to know How
do I verify the secondary coils are functioning since once bought even if
defective the item will not be replaced.
Please guide me on this issue.
You got a good question. Since the winding is too small thus the ring tester kit would not be able to detect the short circuit. Usually the secondary winding would not give problem because of low voltage/current produced. What i usually do is to make sure that the winding is not open and the primary winding is good. If the smps is working fine, definitely there will be output from the secondary side. Now, look at the filter capacitor voltage at the secondary output line. If the capacitor is rated 16 volt, then you should roughly know the line is about 8 to 12 volt. If you get 2 to 4 volt then you know the line or the winding have problem (assuming all other secondary outputs are tested good).
If you have other question please do email me again.
I purchased two of your books. Repairing LCD Monitors and Testing Components.
I originally purchased your Repairing LCD Monitors book because my used 19″ LCD Gateway Monitor stopped working.
Thanks for the support on my ebooks.
A friend gave it to me because it wouldn’t turn on. So I took it apart and discovered 5 bad capacitors. I changed them and got it to work great for about 6 months. Then it started to have long delays coming out of power saving mode. Sometimes it would take as long as 2 minutes before I would see the screen reappear. Then one day it wouldn’t do anything. No power light, no blinking yellow light, nothing. I took it apart thinking another cap had gone bad but couldn’t find anything obvious. So I purchased your book Testing Components and started testing. I think it’s the voltage regulator (KIA7812A) or a MOSFET (K2645). Am I on the right track or should I be looking elsewhere?
When I test for DC voltage at the connector pins that connect the power board / inverter board to the main board with the main board disconnected I have 12v and 5v respectively.
That means the power supply is working thus you do not need to replace the K2645 and voltage regulator IC KIA7812A.
When I connect them together I have 12v but only 1.5v at the 5v pin. Do you think there is something wrong on the main board that is causing the 5v pin to drop to 1.5v or is this normal?
Yes it could be the mainboard have something shorted that cause the 5 volt to drop or the 5 volt line it self have problem that can’t withstand current draw from the load (mainboard). Try touch on the mainboard to see if there is any component get hot or not.
Without connecting the 5 volt, use analog meter set to x 1 ohm and measure the 5 volt line and the cold ground to see if there is any low resistance when tested it both ways. If you got low resistance, that means there is component shorted in the mainboard.