Electronic Repair Questions/Answers and Testmonials- Part 63
I had purchased your ebook few days ago and as I am reading it, it reminds me during my school days at my electronic course it is realy more convenient and very much easy to learn compare to our practical period. Its realy great that you have this kind of ebook and for me it realy refrishes my mind on how to test properly an electronic components and i am very much thankfull that i have your ebook its now my new guide on my trouble shooting activities on my job. Thank very much.
I hope you are well. Just want to thank you for the tips in your September 2010 repair newsletter.
By the way, I found your e-book “Testing electronic components” very useful.
I have Samsung Syncmaster 753s CRT Monitor . OSD screen comes on screen Automatically showing Control locked message.
I have tried by pressing Menu button for 30 seconds & also replaced the front panel but no effect. So please tell me where is the problem.
Check and replace the 7805 IC voltage regulator.
FAN7601 – Green Current Mode PWM Controller …
it’s an eight pin 8pin dip IC.. I have attached the circuit diagram… any idea if we can reset the Over Voltage Protection for this? any way to measure this type of IC?
The OVP can be reset when you turn off and then turn on the set again. In your case, i suggest that you directly replace this ic and retest. You may also check the supply voltage first before you replace the ic.
In fact, under the non polar cap 103…was this symbol..which I couldn’t find in my ref book..what does this symbol mean ? does it mean this is a AC capacitor? I replace it with a DC non polar cap of 103 , 1KV…
Do you have any record on this symbol?
This symbol is a Thermister symbol:
Thanks for the updates and your support that encourage me to keep going on this test of my skills. I have passion in electronics and IT but my weakness is I dont trust myself. I need support and backup, im like that. But now i feel like im one step forward coz I have two books now. I am young and strong and I want to setup my own small electronic repair shop haha..
Good to hear that and nice to know you.
Im still working on my CRT TV Sanyo Mod No CP21SE1 and I’ve just found my part on this web Audio Lab shoping Cart just now. I was upset two days ago when I cant find my part and i set to take my tv to the repair shop. NOw im happy again and your right about wasting time to find the parts, not easy for me.
I go thru my TV again and found the Ec 220uf 160v and a diode short. I have no idea how to find a repacement for this diode only 3AMRU written on it. I only have a digital meter but Im worried coz most of the things in the book is better to use analog and etc. Anyway i have some questions please.
Q. Is there anyway that I can get a circuit diagramme for CRT Tv from somewhere?
Yes you can try http://www.eserviceinfo.com
Q. What exactly posistor looks like and what symbol for it? I suspected a square component (two legs) in the power supply circuit is short but im not sure what it is cos only 180m Cm64 written on it.
It has two and 3 legs and usually black box in colorhttp://www.donberg.ie/pics/p/posistor_69-1.jpg
Q. What should be the output voltage for the filter capacitor in the power supply circuit? Im curious cos i only get 12volts when i test it but its a 400v 220uf capacitor.
It should be about 300 to 320 vdc.
Q. Where can i find the internal capacitor ( flyback transformer) on the circuit board?
You can’t find it on circuit board because this is a film type capacitor and usually can only be found in flyback.
Thats all im confusing about this detective work im doing. Im sorry for taking your time but please not to worried if your busy I can wait.
I need your help in this matter. I am working on a Plasma tv 42″ and I there is something wrong in the power supply that is so strange and I can not locate the fault.
when I plug it in, the 220 volts go to the socket then to the bridge rectifier and then it comes out of the bridge rectifier to the main capacitor. there is 300 volts reaching the capacitor but it is not holding the voltage. it reaches 300 volts then it starts to go backwards in value..what could be the problem.
Try remove the power IC and retest. Sometimes a bad Power IC could cause such problem. Make sure you discharge the bif filter cap first before touching on any components.
How are you, I hope you are doing well ,
I’m fine thank you.
I have one coil which I suspected, by blue ring meter it shows only one red led. And by measuring by digital ohmmeter it shows 1 OHM
That coil is good because blue ring tester can’t test such a small coil. For any small coil, an ohmmeter to test it is already good enough.
how r u
in last month i buy blue ring tester and smps book
i gained lot of information from the book ,which i was not knowing.
i really thank you very much for writting this book
Jestine,i found two TV problems:
1-A leakage of high voltage through the high voltage anode cap,i tried to stop this sparking upto that i can but coud’t stop it.what is the cause for this how can i solve it.
It could be the B+ voltage too high that increase the high voltage. An increment in high voltage could cause it to spark to the nearest ground. Please make sure the B+ voltage is within spec.
2-About the horizontal and vertical deflection specialy the horizontal part.How the horizontal circuit that holds ceramic capacitors (their capacitance rate is 1.6KV,560J…etc),the inductor coils and the diods.how they fanction,how their rate affects the deflection.please,give me some explanation.THANKS!
All these you have to refer to tv repair book because i do not cover theory.
the adapter out put is ok. and the battery is also charging but when i press power button the battery indicator go off and the laptop wont power up. is that power ic or power switch problem
Than i guess you may need to open up the laptop and check on the voltage regulator IC in it. Sometimes a bad power adapter could measure okay but breakdown when connected to a load which is your laptop.
Hi Jestine Youg
The problem I keep having is this is the fourth lcd monitor Ive replaced in a machine .They would all have the same problem .They would turn on a brief second then turn off .The green on or go light indicates its on, but no pitcher.I can turn them off again then on again and the same thing would happen!!!!Having very
little knowledge about electronic were do I start and what do I look for thanks JC..Ps they all use to work
In this machine but over time 1year of so this starts happening ,also Its a pretty warm environment for a monitor..
First check that all the electrolytic capacitors are good then check for dry joints in the high voltage transformer. If all tested okay then replace the backlight as a fail backlight could cause such symptom.
I was working on a electronic board that is part of a computerized flight simulator. The complaint was that a student damaged the sim by static electricity from his finger to a metal part of the simulator.
I discovered that a programmable IC chip was damaged and the program to rewrite the damaged chip was no longer available. My only option was to send the damage chip in and have it copied to a replacement chip. To my surprise the chip was copied successfully and the sim is up and running.
I did not think is was possible to copy a damaged chip to a new chip and have it work successfully. Let me know your thoughts.
The programmable IC actually not damage, only the data had corrupted so reprogramming it will solve the problem.
Thank you for your interesting tutorials on switchmode power supplies,iam currently having a problem with one,interially its output power is 48 volts,it has a problem and its giving me 28 vols,i suspected capacitors,diodes and i have carried out a tharoughly check i could not get the deffected component,it a power supply for a radio transmmiter a mean well rsp-1000 single out put power supply.
How many voltages this PSU produce? Sometimes a e- cap and increment in current sense resistor could lower down the output. A shorted component in the load also would cause the supply to turn low.
I have a Sharp 32″ TV ,model LC-32SB220U.I changed the mains filtering
cap and the MOVs.After putting back everything ,the set is now
blinking power light only. May you help me on steps to take ,so as to resume it.Again I changed mains caps, MOV in a Mitsubishi set , model :WS-A65. On power-up ,a clicking sound is projuced.I removed power,then
check,but nothing was blown.Is this normal?.
Power light blinking-is the output voltages from the power supply fluctuates or steady? If the output voltages steady then the mainboard may have problem. If the output voltages fluctuate then the power supply may still have problem.
Thank you for yours very quick replay,I have one another question/advise from you when you feel compfortable give me replay/advice as you like.
This problem,i face its challenge for me,I repair one powersupply which part number is cppwdaa manufature by Geopower in USA,no more exits now,I reapir several powersupply during previous years,but i stuck one problem during trouble shoot,(Early 80s Technology)in side there is one control card which is Sold in main card,they consist lot of transistor,resistor,opto isolator,diode,and 2 realys,during trouble shoot,i cannot measure voltages in card,because its not reachable and more i dont have diagrame,this powersupply use in HITACHI PABX, can you advised me what can i do?i am sure you trouble shoot this type of powersupply
I have no repair this type of card before. In order for you to test the voltages i suggest that you solder some additional wires on certain critical points in the card. From there you can judge if the particular section is working or not. If it have abnormal voltage then you may need to remove the card and check on the components in that particular section.
sir what is the problem of monitor which is,white screen,no display image?
Screen voltage (g2 ) too high or g1 voltage is too low. You can check the voltage at the CRT board. G1 should have -10 to -80 vdc but not zero volt.
i have one LG crt television set that does not displaying but i use to hear any program that may be going on whenever i put it on.what might likely cause the problem
i will be waiting for reply
It could be missing high voltage or the heater circuit is not functioning. You need to confirm first that the high voltage is present by checking the B+ voltage entering one of the pin of flyback transformer.
greetings. I already did that and every thing checked ok in that section. yesterday I tried a different approach to repair this and it is a very good start.
I think that the tv is going into a shut down for some reason..some kind of protection on that and Mr
When it can’t be turned on quickly check onthe supply voltage to the pfc ic and measure the signals of the optoisolator IC. The most opto ic i saw was 3 but yours have 5! I believe one of the ic or related circuitry have problem preventing the signal from the CPU to trigger the power section through one of the opto ic.
Everything is ok and in good health too-thanks.
I’m also well except I’m struggling a little with a LCD monitor Acer widescreen ModelX193W. I wonder if you can give me some advice.
What happen when you switch it on is that the backlights switches on then off and on again and the off again within 5 seconds the it seems that the on light goes from blue to yellow which I presume is a sleep state. I’ve measured the VCC pin from the main board and get 5V also measure the on/off signal which gives me 3.1 Volts.I’ve checked the backlights and they seem to work fine. I also solder each and every capacitor out to check for any faulty filter caps. balast caps etc. (I’ve repaired almost 15 screens already this year where I worked and 14 of them had blown capacitors and the other one had a pico fuse that was blown.)This Acer got me by the …..hair.Hope you could help. I cant see any information on the inverter IC so I don’t know where the VCC pin is and the pin that would have voltage after the start transistors switched on.
I include a few photo’s to show you what I’m dealing with here. Any suggestions? I must say after I bought your e-book I have a better understanding of LCD’s.
Thanks for the support on my ebook. Acer LCD Monitors have lots of MCU problem. The power LED signal is coming from the MCU in the mainboard. If all the voltages to the mainboard and MCU is steady and you have plugged in the VGA cable then suspect a bad MCU. Just incase if you want to check the inverter supply pin, just place the red probe on any pin and if you get 5 or 12 volt (it depends on the what part number is used) then you know the inverter ic is receiving supply voltage.
Please update me the status of this repair.
Have a good day!
I have problem with internal power supply of ecer LCD model no.
AL1511. I have checked all the componant but found no sign of burnt of
crack. I have check the
again i have check a IC CG6841 and found that i am geting requird
voltage at pin no. 3. i have check the Filter capaciter and measure
the vlotage and gets 380volt. so lastly i had check the SMPS
transformer by multimeter but is seem it is good. i have measure the
out put of SMPS but i have not geting the output voltage of SMPS.
There fore i would be greatful to you if could help me to slove this
problem or the method i have used to check the smps or other componant
is not correct or What? I will be looking forward for you propt reply
with LCD repairing guide in short please
For the power ic, getting the rigth voltage does not mean it will produce output. I suggest that you directly replace the power IC and retest since you said you have checked all the components.
Good morning and hope you are good. I have a query that i think you may
help me. I am working on a mixer and on the amplifier output circuit,two
0.5 ohm 5w resistor will go over heat with the speakers connected and
the mixer shuts down, will come on when the resistors cool down.There is
a thermal cut out fuse before the speaker output terminals. All the
driver, output transistorsand resistors all tested OK. The out put
circuit is a emmiter follower and i have tried to increase the wattage
of the the resistor to10w,but it does the same. The output transistors
used are 2SA1943 and 2SC5200. Any thought/ideas to go about with this, i
dont have a schematic for this mixer. Dont boarder replying if you are busy.
I have not fixed any mixer before but as a rule of thumb if a resistor get hot, along the line there must be components that is leaky or shorted that is drawing too much current. Just check the components along the resistor output line and hope you could locate one.
Thanks for replying
Sorry i do not have info on the latest HV probe. I guess you many need to email them. Usually old model will be replaced by newer model and it is very common in test equipment.
Hei,jestine how r u?here i`m want to share with u my problem about my desktop ok.
The power is good from cpu and deskto also fine,but after a few second when they run
the screen on desktop become black but the writing on the screen stillcan see a little bit so
where is a bad here from cpu or from lcd monitor pls jestine help me.thank`s gd bles you.
I guess is the lcd monitor because if one of the back light have problem it can shutdown causing the display to go dim. You may need to open up the lcd monitor to check for bad e-caps first before replacing the backlight.
thank you for your mail,but repairs seem to be interesting and of a great challenge,its giving me a new nature of fault when i remove the fans iam able to get the output of 48 volts dc and i tried to connect it on the transmitter it was able to drive it but it was charterling,iam suspecting the ic(pwm) becouse all seems well but why could the fans make it fail?, i checked on its circuit all the components are ok,another suspect is the choper transformer its giving a sound as if its trying to switch on i press hard on it the sound goes advise
I suggest that you directly replace all the filter caps in the secondary side because a bad filter cap can produce good output but when there is a load (fan), the voltage will turn low. Try change the cap first and see if the sound will go away or not.
Good day mr justine i want to confirm if i can determine an electronic component
if it is missing not using a diagram is there any other way i can determine a
Only through experience. If you are a seasoned electronic repairer for a particular board and that board have a missing component you will roughly know what value you should put in but there is no guarantee about the machine will work again. The best is till with the help from schematic or from comparison with the same model.
good again mr jestine is it possible to match a sony chasis to a L.G. tube it has the same pins on its crt i mean this lg tube is a double focus crt pls.correct me if im wrong coz i am a beginner and i am really interested to be a succesfull technician
The part number has to be the same or near the same because different spec will cause the HOT to burn or the display will have problem.
This LCD monitor is imported as second goods from japan, and the seller has modified the AC power to 230V, see the series filter cap. After the customer used this monitor for a month, the monitor becomes totally dead.
By the way, how to correctly modify lcd monitor from 110 to 230V AC? Is only replacing the filter cap will do?
If it use power fet then change it to 600 volt spec like K1118 OR K2645.
Now I have found a secondary SMD diode written BC49 has shorted and don’t know what to replace that with. It is loacted between the black tape securing the series filter cap and the SMPS transformer ( see the photo ).
Sorry no info about the diode. Try use Uf5406 as replacement. If there are two similar diodes i guess you may need to replace the other one too.
Do you have any idea what other parts may also have problem?
I’m not sure with this model and i suggest that you check all the components in the primary side.
I also found the voltage of the power IC ( pin 7 VCC ) ICE2A365 is fluctuating between 10 to 12 V. Do you think this IC also went bad?
Hard to say, it can be this ic problem or bad corresponding components.
This is the neatest design I ever see of a lcd monitor, all components except the lcd panel are placed into one board.
Hope you another success with your fifth e-book
I have an old Sony VCR player whose smps is behaving strangely over the years. Problem is at room temperature, when connected to the mains, the smps will not start up (there is no indicator on vcr display). But if I open the vcr cover and directly heat up the metal shield casing (which houses the switching transformer & fet and secondary circuits) on the smps circuit board directly with a hair dryer for about 1 minute and then connect to the mains, the vcr would then power up and behave normally (can play, forward, rewind etc). Problem is, if there is an interruption in the mains power supply for more than a few minutes, I am back to square one again.
Have you come across similar cases or have any idea which component(s) of the smps is causing this problem? Thanks.
It may be the problem of dry joints, or bad e-caps in the power side . I suggest that you take out the power supply and examine but make sure to discharge the big filter cap before doing the repair work.
Have a good day!
hi!Jestine,just wanted to thank you ,for doing such a wonderful
job……the sort of information you are giving is surely benefitting
to all technicians….
hi mr jestine.
can you send me a picture which include dry joints?(i want to see what
shape the dry joint is.)
thanks a lot.
Try this link:
i m fine sir and hope for the same to you..
thanks a lot ..very nice article you have been post on the site is much usefull and instruction given by you with pictures makes it more attractive and knowledgeable .your way of depicting the problem with figures is alway appreciatable ….
Good Luck for all joys in you life
bye take care
i just have a question, how to identify a immatation & a original component part?because here in the
Sometimes it is hard to see if you do not have the original part to compare. May be the HOT blow because some other causes that can be found from this link:
Your Name: Alex
Message: Just want to say thank you very much for your site and instructions on repairing Dell E152FPb monitor. I was able to fix my monitor for $3.00(fuse cost). Started looking for the blown capacitors first, then found your site and checked the fuse. That was it.
I am not an electronics repair guy. I work in machine shop, but I like to tinker with everything. Your instructions were enough to help me with my problem.
Again, thank you.
Thanks for this month newsletter, that will help speed my repair work.
You are welcome!
The problem of this CRT monitor is display always white whatever signal pattern being injected and when I press the menu button, the color of the menu can hardly be seen ( washed out ) since being covered by white display ( not too bright actually ). After opening the cover I found no screen pot on the flyback, only double focus pot. What could be the problem of this monitor? I haven’t experienced this kind of a problem. It’s pity that I haven’t taken the photo of the display due to the following cause:
Try measure the G2 and G1 voltage. Sometimes a bad resistor in the circuits could cause such problem.
Unfortunately, someway I had lifted a little ( not totally detached ) the socket of the deflection coil and forgot to firmly pressed it and turn on the monitor, guess what happen? The monitor is on ( white display ) for about half a minute and then went dead. After checking found the HOT 2SC5589 blown ( PC rating 200 Watt, see the photo)! Now the big problem is I cannot find this genuine HOT locally and don’t know how to explain to the customer since the problem is getting worse. This 17″ CRT monitor back cover is written consuming 2 A ( see the photo ). I wonder why this 2002 manufactured monitor uses that big HOT. Do you think I could replace it with C5411? Or you could give me another common substitute?
You can try that and you may also use C5407 to use as substitute.
Is that true if powering on the monitor without the deflection coil attached will kill the HOT?
It depends on model, some will Shutdown and some will kill the HOT.
The september newsletter was really of great help.This can no doubt speed up the repair work,as most of the time the culprits are burnt/leaky components.
But this time i need your help in successfully dis assembling a CRT tv.
My doubt’s are:
*How to remove the Anode Cap,that is connected or comes out of the fly back transformer of the CRT?
*What are the precaution’s (if any),that must be taken in removing the Anode cap?
*How to again put it back?
You may visit this video:
after discharge just take out the anode cap with the help of long nose plier.
I’m repairing a Philips blender HR2898.
This is the motor PCB.
On it, there is a (I think) diode (measuring open), which I have never seen before with a blue band in the middle, and I’m not sure which is the anode end.
I’m not sure if that black mark on the lead at the left is significant.
It comes off the gate of the BT138 Triac – usually the anode is at the gate, as I understand.
Have you seen this type of diode with a blue band in the middle?
Thanks for the photos. It is a diac if I’m not wrong and diac should have open circuit reading even under x 10 k ohm range.
Compare to this circuit below:
Look at D1.
I had bought a Blue ESR meter for capacitance testing.
Can I also use it for testing ceramic/non-polar capacitors.
Yes you can use it to test on non polar cap from .1uf and above and you need to draw your on chart for non polar cap.
i have come across a dead television repair, when i open the unit i immediately check its HOT transistor and found out that it was shorted… i replaced it with a new one but when i turned it on it worked but lasted only for 15minutes. i replaced it for 5 times but still it will only last for 10-15minutes and shorted again. i’ve tried to check its sorrounding components but finding another faulty components are imparative. i just wanna ask some tips from you of what would be the probable cause why the transistor keeps on shorting. thank you so much and more power to you.
the unit is Goldstar CN-14D10G
Please visit this link:
I’m very much appreciated your email.It is 100% exact we need as a electronics repair man. By the way , I was in K L last July 11 to 16 of the machine training of BESI APAC at SHA ALAM. K L is a nice place also, hope I can visit soon to your area.
No problem and you are always welcome to my humble office.
Amazing testimony for you, I’ve got a new job in Singapore and next month ( 1st week of October ) I start to work and I will invite you to visit us in the Hotel.All your information regarding the electronics repair I used during the personal interview and I accepted for the new job.
Thanks for the invitation but at current moment I have some projects. My family, friends and I might be going to
One of the question’s, during the interview :
– What is the procedure to repair the printed circuit board?
– How to trouble shoot the power supply circuit and how to understand the power supply circuit?
– How to test the common transistors and diodes using digital meter.
– What is the procedure to make the printed circuit board?
All this question I’ve got the right answer’s because I always read your electronics repair guide letter’s and link to update my knowledge about basic electronics repair.
Wow! i did not know that my information has helped you in landing a job. Congratulation!
Thank you for the continuous us sending electronics letter’s update.
You are welcome!
Next month I’ve plan to buy the blue ring and ESR meter from you.
Long time I wish to have this tool.
No problem just let me know.
All the best!
hi jestine ,
how could you test the fly back internal capacitor is it on circuit or not?, does the blue ring can identify a shorted internal capacitor?, and lastly how could you locate the pin of the internal capacitor in the fly back?
Here is the link that you can refer:
Would you mind enlightening me on the use of opto-couplers,
their uses, types and mode of testings.
You may visit these websites:
My P3 PC PSU is bad.
I have tested it and found out that there is high voltage DC supply
up to the transformer terminals but there is no output at any of the
device connector terminals; not even the fan working. Please help.
I suggest that you check all components in the primary side and also for bad secondary output diodes in the secondary side. If all check to be good then direct replace the power ic and retest.
I am in the computer reselling business and have been for the past 18 years. I have always practiced exchanging faulty boards with new ones and outsourcing monitor, lcd & notebook repairs.. thank you for opening up a new revenue stream for me, I now repair almost everything in house.
You are welcome and the success also depends on how hard working you are.
On testing for shorted components with a “DC Regulated Power Supply” can I use that technique on Notebook mainboards ?
Good morning sir! here is some feedback for the March 2009 (LCD repair).
After reading your article, i am able to repair one of our LCD touch screen display. At first repair work (without reading your article), i do not know where to start until i read through of your March newsletter.
You might be interested to this brand. Here, i am using Huntron Tracker to find the faulty component. It is very2 useful. http://www.huntron.com/products/2800.htm
I hope you are doing well. I have two TVs with problems.
First one is Daewoo. The bottom half of the screen is black but the top half is blue.
Check the vertical area for dry joints and check also the supply voltage to the vertical IC.
Second one is Philips. It came with the Horizontal output transistor shorted. I cheched for the cause of the short but found nothing so i replaced it. When i press the power button, the power LED lights. The G2 voltage delays at 8V for a few seconds then increases abrutly and immedialty falls back to 8V. When it does this i hear the usual sound behing the tube but it dies off quickly as the G2 falls and tube does not glow. The Power LED remains on but the screen is blank.
This could be high voltage shutdown problem that’s why the HOT shorted. Check and make sure the B+ supply voltage is good.
while searching about monitor service in google,i found your site.it has very use full information.
and i have a samsung monitor model 594MG with following problem
1.when switch on the monitor it show full of brightness and retrace lines.
i tested G1 it showed 30 some time 60,
after some time it gets 70 the monitor works well
2.moreever when switch off the monitor in centre of screen one white dot is coming why and what happening
give me solution to solve the problem
The G1 has to be stable with negative voltage and i suggest that you check componens along this line.