Electronic Repair Questions/Answers And Testimonials- Part 39
Got your newsletter few days ago, but unable to reply earlier
due to some avoidable circumstances. Factly, I’ve learned so much from
you. You are a great help. Thank you very much… God Bless and more
Your LCD Repair Manual was a great help. We save almost $5,000.00 for the repair of 10 units of professional LCD monitors.
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Order Date: 2009-06-23
Thanks for your constant letters which are very helpfull to me. I am learning alot from your notes and newsletters. I haven’t began doing any thing practically. I still need to acqiure some tools and testing equipments.
However, the knowledge I have got from your literature is tremendeous
Hi Jestine ,
How do we know the eeprom is ok or not ? How to test it or what symthom if it’s not working ?
Good question. The best is direct replacement with a good eeprom. We can’t test it with scope or even voltmeter. Symptom depends on the equipment you are working on. For example in CRT Monitor it can cause display to shutdown, missing OSD, OSD out of position , horizontal width big and many more.
I’m diong repairs every day but when it come to CD & DVD player repairs
then i dont know where to start .
Cleaning the optical lens is the easy part.
Working on the power supply is ok
There is power supplys that take time to repair but when it gets to the
prosessor board then im lost
Jestine my question to you is–am i waisting my time fixing cd / dvd players
or is there something that can be done.
PLSE i need help..is there information that i can download from the
For CD/DVD player if it shows the no disc error symptom check on the spinner motor. A lower rpm would cause such problem. Please click on the link http://www.repairfaq.org/sam/cdfaq.htm
No you are not wasting your time infact you are learning/adding something new into your life!
please do you have any book on how to test ic’s
i need it for my project
Sorry i do not have book on how to test IC. To test IC you just need to locate the datasheet and find out the supply voltage , output and input pins and then test out the waveform.
refer to electronic and technology news
why horizontal out put tansistor in crt monitor get shorted?
you are talking in this aticle about B+ voltage but you did not explain that what is B+
voltage and from where is coming . please tell me what is the source of B+ or
give me a link for more study
Here is the link https://www.jestineyong.com/?p=403
B+ voltage is from SMPS and usually have about 50 to 80 VDC in CRT Monitor and 110 vdc in CRT TV. This B+ voltage is required to energize the flyback transformer.Hope this helps!
i have two more question refer to why HOT get short
1-you said that you ck the horisontal driver circuit area was running at diffrent frequency
from normal setting of monitor. the question is by frequnce meter you ck that or by what
kind of equipment you did that?
2-where is the location of safty cap in monitor
I check the frequency using meter because my digital meter have a frequency range. The safety cap is located nearby flyback and usually have a voltage from 1600 v to 2000v.
Hi Jestine I have couple of enquiry about TV repair, just want some information regarding testing of flyback transformer which i have test it with my own built tester that you send us i assemble this tester and it absolutely work ok.Now to proceed my testing of flyback transformer B+ to HOT all 8 lights on means ok and the secondary winding also series winding all led on frm center tap 3 led on now the heater circuit is this normal the heater circuit it shows shorted no led on all off?.
Yes this is normal because secondary winding have less turn as compare to primary winding.
My other enquiry is if no signal to HOT there will be no output also?
Yes that’s right!
because the dropping resestor that in series with the input transformer become hot and drop to 3 volts from 100 volts is it because driver transistor is not activated due to no signal?
There is something shorted and not due to missing signal. It could a shorted driver transistor, e-cap,or even the h. driver transformer.
Thank you very much God bless you always.
You are welcome!
sir good pm,
can you help me i have AOC monitor which is the menu configuraton is in the leftside of the screen not at the middle,the brightness is 100% already, but it seems its dark can you help me what im going to do..thanks
It is the eeprom fault and you need to reprogram it.
Your Name: Senay
Message: Hi Jestine
Would you mind if you introduce me with SMD rework station and its application in electronic devices(I mean how to use it?)
You have to practice it using junk board. Just set the blower to about 5 or 6 and the temperature to about 400 to 450 celcius. Again it depends on what components you wanted to be removed.
dear sir i have dell lcd 17 inch
(C5707) inverter side
this transistor is damaged . i changed but he give display within 2 mint the display gone.
but LCD light is on ( On off LED)
i think the lamp problem he have 4 lampe
can u tell me wht should i do plz sir reply me early.. if u have any online ID plz tell me
Please check the tuning cap, dry joints at high voltage transformer and the p-channel fet for shorted.
I came across one CTV with colour problem. After replaced the ‘problem’ posisitor, the colour back to normal.
My question is can the ‘problem’ posistor cause the CTV power LED to blink ‘on’ and ‘off’ along with the power Relay swtich having sound ‘tic…tac’. And the CTV cannot start up.
I have not seen any bad posistor causing such problem. Usually it cause color patches or blow the fuse. A shorted flyback or components in the secondary side could cause the problem you have just describe.
Have a good day!
I came across one dead set CTV in which the fuse is not blown.
After I check with the multimeter, I found one opened transistor (MD1803FX) and one burnt transistor (2SC3807) in the primary circuit of SMPS.
Later I found one more shorted capactor (250v / 22uf) near to Flyback.
After I replaced 3 of them. When I switch on the set, it remains dead.
I desolder all the secondary pins of SMPS transfomer and measure all the pins. All of them have not voltage.
At the primary side only transisitor (MD1803FX) has voltage but not transistor 2SC3807(all 3 pins has not voltage.
What do you think of the problem.
You can’t test the smps transformer offload because it could blow the power section components. I guess you recheck all the components again or use the isolation method in this link;
1) Do I have to calibrate the ESR meter every time I switch it on by shorting probes and pressing power button momentarily? If I don’t do that, I noticed, the meter doesn’t show correct reading. In fact the test probes must be at least 6 more inches long because its being pulled by the probes when we bring it near the equipment under test and causes inconvenience.
Yes you have to in order to reset the microcontroller. If the test probes is too long it will create an inductance and affect the meter reading.
2) Can not we check HV Ceramic or polyester capacitor, the blue one like safety capacitor with the ESR? When I did it didn’t show any readings.
This meter is in fact was design to test on electrolytic capacitor and not non polar cap. You did not get the reading because the value of the cap is too small
3) What’s the function of the loop wire in attached picture that’s connected to the board from FBT, in a CRT monitor.
To synchronized the frequency of the smps and the secondary side.
4) In your book ‘TESTING E COMPONENTS’ it was not mentioned about Diac but I’ve heard name. What is it?
Diac rarely found in consumer electronics thus i did not write about it. Here is the link about Diac:
Thanks very much for your support and earlier replies
Still waiting for your 4th book to be released.
Thanks for the support of my fourth ebook and completed about 95%.
I am faultfinding my first SMPS and your article on the 3842 PWM chip and testing the transformer is a great article and it helped to find the faults.
PS. Keep up the excellent work!
I have one dificulty could you please guide me how to test SMPS (Cold testing & Hot Testing)
To check primary side (hot testing) place your black probe to the negative side of big filter cap and place the red probe on the point you want to measure. For cold testing, place black probe to chasis ground and your red probe to any point you want to test.
What is power good in SMPS ?
Power good is a status signal generated by the power supply to notify the computer that the DC operating voltages are within the ranges required for proper computer operation (+5 VDC when power is OK)
The TV doesn’t switch on.Primary side of the power supply i get all the
voltages including 320V from the big capacitor and the fuse is not even
blown to show that the primary supply components might be faulty or
short circuited by any chance..
My problem is with the secondary side of the supply,were i surpose to
get 120V on the Vce of the line transistor(D2499) i get 25V to 39V of
which its too low to switch on the TV.
These voltage of 25V-39V you only get it when the TV is on stand by
mode,but these TV is not on stand by mode its completely not switching
I suggest that you follow the procedure from this link;
what do you mean in your book that a intermittent diode could located using a coolant spray (example) and hair blower ?
Some diode or semiconductor after warm up may give problem and when you use a coolant to spray on that particular diode the problem could stop and you will know which one is the culprit. Using hairdryer is to speed up the process so that you will not have to wait for the diode or semiconductor to give problem. Hope this helps!
I am faultfinding my first SMPS and your article on the 3842 PWM chip and testing the transformer is a great article and it helped to find the faults,
You are welcome!
The primary side of the transformer winding is bad, the FET was shorted and the PWM chip was damaged but yet the 240v supply fuse didn’t blow?
It could be the short circuit was not that severe and the current draw was not that high thus the fuse did not blow.
If I want to replace the SMPS transformer how do I know which one I need and can I use another one, if so how do I match them up as in do they have markings on them that identify the output etc?
Funny thing about SMPS is that they are uniquely created because all SMPS design is usually different. Due to this you will not find any substitute transformer. The best is to get back the same transformer from the manufacturer/distributor. The marking on the transformer could only be understood by the manufacturer/distributor.
Hi, Jestine, How’s everything go on. I have a HP 5500 CRT Monitor which always OSD intermittent appear on the screen. I thought i was contact point board, Soldered it and
it the problem came back again. What’s the source problem of it, Pls tell me, Thanks.
It could be the eeprom data problem, bad crystal or even bad CPU.
just bought your guide. its very good. i have a problem with a monitor
that changes to all green, red or blue when i turn it on. no text is
visible just solid color. any suggestions where to start looking for
fault would be greatly appreciated.
If all the connection (VGA cable) from the CPU to the lcd monitor is good then suspect a bad mainboard.
Message: i am looking for a ceramice disc capacitor made by TDK. my problem is that i do not know what its replacment part is. i was wondering if you have any knowledge. the board goes on a vehicle display panel. i have these numbers on the ceramic disc:
05115 under these numbers i can read E3SF-AA then TDK. i would like to replace it but i do not know what value it is. any ideas would be great. thanks Edward
I guess the numbering is the manufacturer code and is not standard capacitor coding. Sorry i do not have information on such cap.
I just wanted to know that, Do we have any site where I can check various IC configuration?
Currenlty I need for “philips – TDA9370PS/N3/A/1665“. It will be very helpful if I can get any site for the same.
Thanks in Advance.
Sorry i do not know of any website that provide IC information other than the IC manufacturer itself.
dear jestine i have a problem with a tv maybe you can help me out, the power supply seems to be ok the red diode turns green and some voltages are correct i have even 130v on horiztal transister but seems to be still dead that i noticed that no HT is coming from the anode of the lineoutput transformer do you think that the transformer is faulty? can i check it with anoulge meter? pls what do you recomanded me or it can be an electrolitic cap?
You need a signal to the base of HOT. Without signal there will be no high voltage.
I have this Sharp Aquos, model LC-20S7U.
The remote can not turn the tv on, but when you turn it on manual on the power switch on the tv, it work normal.
You can switch it off with the remote. I have two of the same tv and both remote have the same problem. I also tried with an universal remote and have the same problem. It can turn the tv off but can not turn it on. Can you help me with this problem?
Ps. Thank you for all your email about the electronic guids for the lcd and plasma tv that you sent. It was all helpfull and good.
Thanks for the email and since i have not come across such problem before thus i could not give any expertise advice on this matter. It seems that the TV is the problem and not the controller. Have you check all the corresponding components in the remote receiver circuit? I wish i have the Tv with me in the workbench as this problem is very challenging. I like challenging work especially in the electronic repair.
I find your ebook very nice and important.
I learn your lesson and my repairing time goes faster.
Jestine i have one monitor giving me problem.
Is not turning on and the power led is not lit.
I check all the power on power supply board and all is correct.
I get 14Vdc 5Vdc and 3.3Vdc.
I don`t now if i do somting wrong.
Jestine I need your help to get rit of thies problem.
Monitor ProView Model: 900W.
I apreciate your help. Thanks in advance.
Thanks for the support on my ebook. If you got all the voltages even to the Mainboard then the mainboard is the problem. I came across quite a number of Acer LCD Monitor with this problem.
I started working on a 17″ flat panel monitor and I found a resistor that looks like it is bad.
The color bands are Red , White, White and the 4th is Gold.
I came up with a value of 29000000000 another web site calculated it at 29000m
Is this correct? What number do I use when buying a new one?
I know about the gold band.
I guess the resistor color band had changed color. I guess it could be yellow in the 3rd color band. Sometimes when a resistor went thru heat the color may vary. For your information, so far i have not come across a resistor value with such a high ohm.
Hope this helps!
Good pm sir. Can a 10 volts zener can be substitute to 8.2 volts zener? if not what will happen to that circuit?
Some circuit can be substituted and some don’t. Since zener diode is easy to buy from local electronic store, i suggest that you use back the same voltage.
Another sir why some electrolytic cap with the same farad and volts but have different physical? is this means that if it small in physical size compare to big physical does it mean that that the small in physical size is inferior in quality? for example i have replace a 1uf 250v which is big in physical size but when i buy for a replacement the one that bought is also 1uf 250v but small in physical size.
It depends on capacitor manufacturers. Small does not mean it is no good. Look for the branded cap
Thank you sir. We HAVE LEARNED A LOT from you.
You are welcome!
You have mention that you have write about computer monitor troubleshooting why you have sell it in the market, i think it will be a great help to other technician.God bless you more.
Because i’m still writing the SMPS book and expected to be ready by October. Besides the demand for CRT Monitor repair information is not as good as compare to other topic.
thank you so muchof your sending the cards to your blog all the members can see the fotos.i have new question about smps power supplies . why designer of such power supply
are not making according smd parts and .they make power supplies with classic type components . this is a technical issue?
Every equipment need different voltages and current to run on the circuits thus the designer have to design according to what the circuits need and not what he want to design. Hope this helps!
my friend has a problem in his LCD monitor. after he watched a movie in his PC,the display in his monitor has vertical and few horizontal dots rainbow colors, after that its faded into black color start from the top going to bottom.what is the cause of it?how can i fix it?if you mind can you help me??please!!!.Thank you.,,And God Bless!!!
If the power supply output voltages is good then suspect a bad lcd panel. Before that, make sure all the internal cable connection are connected well. Have a good day!
Thank-you for your swift reply. I have one other question and that is how do I know which settings to use on my Oscilloscope when measuring voltages/waveforms?
It depends on whether you want to test DC or AC signal. If you want to test DC then set to DC and play around with the voltage/division setting until you get a straight line. If you wan to test AC signal (waveform) then set to AC and play with the voltage and the time/division until you get a waveform. But of course you must know where to place your probe (testing points) in the board you are repairing. Hope this helps!
I have been given a task on design project. They said I must design the following project:
“LISTENING DEVICE FOR BIRD WATCHING”
I am required to develop such a device with the following minimum specifications for the unit:
1. Handheld, battery operated.
2. Frequency operation in Audiable frequency range.
3. Minimum of 30dB signal amplification.
4. Volume control for final output stage.
5. Automatic gain control.
6. 10 second recording of sound, non volatile storage.
7. Two output sorkets for headsets, 5mm jack plug sockets.
8. 5 hour operational capabilities on one set of batteries.
9. On/off switch with LED indication.
10. LED to indicate recording.
11. LED to indicate playback.
So I want you to help me on how I can design this project.
Looking forward to your respond.
Sorry i’m not in the designing field thus i could not help you on that. However if you have any electronic repair question please do email me.
Have a good day!
Hi Jestine – About 2 years ago I was give an Acer AL712 flat screen monitor by a friend. The only way to get it to work was to push the on/off button about 30 times. Then it stopped working. In desperation I Googled: “Acer AL712 – power button switch won’t work”. Google listed your site and the diagrams you showed were incredibly clear and it cost me about 50 cents(in USD) to fix (R2-20) in
Many many thanks.
Please let me know the equipments/tools that electronician must have. Is it enough just to have a soldering, a tester and some screw drivers to check and repair electronic appliances such as induction cooker, tv, hi-fi, hand phones and so on. Please give me a list of these equipments so that I can get it from the nearby shop.
You need analog/digital meter
Blue esr meter
Blue Ring Tester
Digital capacitance meter and
2. I am also interested to knowing more about the function of transistors, capacitors and diods.
That you have to read from electronics books as it has more indepth explanation.
3. Whre actually can I buy electronic parts?
Try the list in my blog here:
A few months ago I told you I was able to find out with a ohmmeter that I had a faulty EHT (flyback) transformer in a large monitor. It was shorted in the primary.
My question is this: why did the primary in the EHT short?
It could be due to the quality of the flyback and something shorted externally that had burnt out the winding like shorted HOT and etc.
I,(try to) repair motor drives , frequency inverters , servo packs, ect. Could you please help me on where to find more infomation,basic fundementals and circuit diagrams for this type of electronics.I also would like your input if you have any advise on how to repair these types of electronic equipment.
Have you try http://www.eservicinfo.com ?
I want to thank You from all my heart. It’s so nice to receive articles about my loved electronic repair.
Maybe I’ll never thank you enough.
Concerning about the value for burned resistors, I think you take into account the wattage(power dissipated) of the resistor and the value of voltage
between the two contacts of the resistor, but thats are not enough (in my mind) to determine the right value. Will you be so kind to give me help to this theoretical problem ?
I’m not using that method to find out the burned resistor. I’m using another way in my find burnt resistor ebook. Have a good day!