Electronics Repair Questions/Answers and Testimonials- Part 76
Sir Yong gd day, what is the function of this K4101. is this a diode? or Power Transistor. my LCD monitor is AOC. tnx God bless
If it is a three pins device then you need to check on this link:
I’m glad i found your site.
I have a question about measuring capacitors. I have a digital capacitance meter and for some capacitors it shows me a variabile value. For example, i test a 22nF capacitor (discharged) and the dial goes 20.1 20.2 20.3 20.4 20.5 20.6 and it goes like this until it reaches 24nF. If that a good capacitor or a bad one. I’m asking because i have some new ones that behave like that…
It could be the cap meter got problem because usually cap does not behave like that. The value will be stable and would not slowly go up.
The computer i was working on Dell Optiplex GX280 after the burn in process, software installation,etc. works fine and was running for about six hours and then the following day it wont boot anymore and the power button is blinking the code said motherboard or power supply. I test the power supply voltage everything is okay and i came across on this online:
Good testing tips for a power supply. I have only
one item to add. After verifying that the DC levels are the right value, re-check each pin checked before, with the multimeter adjusted for
AC volts, not DC. And of course, the proper range.
What this does: the multimeter is now looking for
AC voltage, and there shouldn’t be any (or very
little). 25- 50 millivolts is ok, but more than this will cause the digital circuits of the computer to work erratically.
The power supply has higher reading on AC. I decided to used my desktop power supply and the computer boot up and also check the AC ripple and it was low (002.2 mv or less). What causes the AC ripple to get high and which part to check? Hope for your proper guidance.
A bad filter cap that have high ESR could cause problem to the line and will usually lower down the output voltage of that line. If all the lines output have ripple or have lower voltage then you need to check the primary side big filter cap. If you have tested the power supply voltage to be good (assuming you have used another good motherboard as a load) then most likely the motherboard is the cause of the problem.
Hi there Jestine,
Okay thanks. The motherboard is fine the power supply is the problem although all the output DC voltage are good its the AC voltage present is high compared to the good power supply and i found a 2200 uf 6.3v is bulging and my problem here is where to buy the parts.I have been tearing down some of my bad power supply,monitor and TV to get familiarized with parts on your books just to fine out the parts are nowhere to be found and if i find it on the web the total charges makes you think twice to purchase a new unit instead.
YOU can install a 2200uf 10 volt capacitor as replacement. Usually i buy my parts from local electronics shop. If you really could not get the parts from your country, the only choice you have is to order it online. Order more variety in order to save the cost of shipping. You can visit this link of list of electronic suppliers:
I have one smps having ic no. SG6105D but i have no details and pin description of the IC. The problem is do not getting output voltage but i am getting violet 5v and green 4.8v, when i short the green black, then there is no output in other pins. I have no idea about this IC please explain how to test this IC and pin voltages.
Try this link:
Look for the supply voltage (vcc) pin, input and output pin. Make sure the voltage is good and stable when measure the ic on board. If the voltage is good then you need an oscilloscope to check for signal at the output pin. No waveform could be the ic have problem or the surrounding components have problem.
I have changed one HOT in 17″ monitor C5802A, after running 15 minutes normally it get shorted again. Please tell me what may be the reason.
Please visit this link:
i got 1 a problem for the inverter 32″ Toshiba LCD( see the attachment )Power ok but no picture…after i opened and checked all the pcb and found inverter board not function well. Fuse 5 Amp was blown and 2 FET FDD 8447L also defected.I already changed the 2 FET and test but one of the FET burn again.I change 2 times that FET but after power on just 3 second after blue screen appeared and cut-off back…..i just want your opinion jestine is it i need to change all the FET ( 4 pcs ) one time or maybe the transformer may be defected…??? If you say maybe the transformer problem how i want to know that the transformer is ok or not.? ….for your information i only have multimeter and ESR meter…tq
Thanks for the photo. It is not necessary to replace all the FETs. First you need to replace with original part number and second thing is that yes there is a possibility the high voltages transformer is shorted. You may need a Blue Ring Tester to check on the winding of the transformer.
I have finally got back to my damaged LCD monitor…I relooked at it, reassembled everything completely AND IT WORKED!!
So a big thank you for your advice and your books.
So my whole problem was 2 blown capacitors…my subsequent problem was that I did not reassemble everything when checking the voltage.
Now if you have the time…another thing I noticed was that one of 2 identical ICs (in the power supply circuit) had 2 legs shorted, so I removed the short. But I cannot identify the IC…it is an 8 pin IC with the markings 4606 BD6G4H (not sure if the 6 is a G or vice versa) – what is that IC and how would I find out what it is?? I have tried the normal internet search.
how are you ? it is long time.
Mr jestine I’m having a problem on certain Sony plasma TV with the
Model No.KZ-32TS1E, when you put it on for some time or for about
half of hour the sound will go off,it will freeze and the remote control also can not operate at the same
time when it freeze and later it will go off and the the red light will be blinking .
but when you remove the mains and plug it will come with picture and go back again
so i really need your help
thank you .
It looks like a tough problem. I suggest that you use a can of freezer (coolant) to spray on the mainboard to see if it have any changes or not. Make sure the power supply have no bulged cap and that all the output voltages are good and stable.
How are you. A friend gave me yesterday a Tektronix oscilloscope 468 (its huge) no manual yet,it turns on and i manage to see the trace on channel 1 & 2 im just curious how to do a simple test on working power supply perhaps or any you can think as simple. Thanks again and have a nice day.
It depends on what type of signal you want to test ie; AC or DC. If you need to test on DC then select DC and turn the volt/div knob till you see a straight line. if you want to check for signal then select AC and place your probe onto the test points and turn the voltdiv and time/div till you could see the waveform. Using scope is big subject and i suggest that you search from amazon.com to look for books on how to use oscilloscope.
The frequency measured by the scope is closely matched with the XTal freq ( 8 Mhz ) as you could see in the photo attached.
If we got the sine wave and the frequency is correct, could we assure that the mcu is working properly?
Thanks for the test result. Even if the crystal is good this does not mean a MCU is 100% good because the MCU programs could run. I came across many Samsung LCD Monitor board that have good crystal waveform but still bad due to the corrupted programs in the MCU.
if you mean the b+, its ok with 114v. i monitor it with digital multimeter and if i change the picture mode to any of the ff.,,pic.user,pic.standard,pic.vivid the screen starts to behave abnormally.intermittent squezzing,expanding for few seconds and when this happen the b+ becomes 94v to 97v so it is not stable.if i choose the picture mode pic.save this does not happen but the default picture setting is not satisfactory to view.you’ve mentioned pincushion transistor,can you pls. tell where it is mounted.and does the screen and focus knob of flyback is similar to a potentiometer?thanks a lot!!!
Yes the focus and the screen vr is similar to potentiometer except that it is in very high ohm (few hundred megaohm). No matter what picture size mode the B+ has to be stable. Have you check the B+ voltage line filter cap? Is all the other output voltages normal? If is is slightly lower then you may need to check on the power supply primary side especially the low ohm resistor and e-caps for bad ESR.
I am working with crt computer monitor ( Proview) and there was a problem with the hight voltage and got it fixed but the problem remained is, I could see the screen lighting up but there is not picture coming on it and there is no stand by light..there is an ic ic on the monitor neck board LM 1237 which have to do with the OSD display..would his ic cause this kind of problems? also I am thinking of the eprom..but I checked, there is five voltage readings on it..may be the ic itself is bad..any ideas..thanks
Yes this ic could cause no picture but have raster symptom. If the eeprom data had corrupted it could also the cpu not to produce any signal to the contrast circuit thus there will be no picture.
Saya nak tanya , adakah kapisitor biasa sama dengan smp kapasitor.
Last training member.
Sebenarnya sama cuma SMD kapacitor lebih kecil. Anda kena pastikan samaada kapacitor jenis non polar ataupun electrolytic.
hai Jestine, sorry dh lama saya tk contact you.
Saya ada 1 LCD Monitor 15” model Samsung SyncMaster 540N.Selepas ON gambar ada dan padam. Saya dh tukar 1 capacitor.kemudian okey. Bila lama pasang ia jadi Balik.
Saya takut masalah MCU. Bila ia dah padam, adakah supply voltage masih kat kaki vcc inverter ic? Kalau tiada voltage maka MCU adalah masalah.
model 17” Hp 1702 ada colour hijau saja ,asalnya VGA cable rosak, dah tukar. mula-mula okey, lepas tu gambar colour jadi hijau. dh tukar tapi masih sama juga.
Make sure cable connection antara mainboard dan LCD panel adalah bagus. Sekiranya ok suspect mainboard ataupun lcd panel ada masalah.
Anyway, i just finished replacing the bulging 2200 mfd 6.3v caps with 2200 mfd 10v (because you point out i could use the 10v) i salvage from my bad Antec power supply on Dell optiplex GX280 power supply.
Yes you could use the cap.
I use this power supply together with the motherboards that i just replaced the bad caps courtesy of TheCapking. So far so good did the test from dell diagnostic disc and the results all pass.Without your book and your support i would never accomplished this.The same power supply was given to me 6 months ago was tag bad and all i care to salvage is the copper wire to sell and it wasn’t that much now i salvage all the parts so i could practice checking and testing. Once again thank you so much for your support and creating such a wonderful books.
You are welcome and keep up the good work!
Thank you very much for this month Repair Newsletter.It is good to read how others are progressing.
You always also care about how your readers are doing (their plans and projects), it makes me feel very good and it is very encouraging.
Since the beginning of this year, I have had a neck injury. I have to change my chairs, table and my way of sitting.
I am now also able to read: I am glad! I cannot hide this to you because you have opened for me a world, a world full of accomplishmen, satisfaction and happiness.
To you my sincere gratitude.
Have a nice day!
There is some misunderstanding, actually C5802A is not shorted, neither previous nor new one. When i checked the transistor out of the board it shows ok.
Actually when i start the monitor then it is over load proctected by SMPS. But when i checked continuity between C-E of HOT at that moment, it shows about 100 ohms that’s why i suspect the HOT/MOSFET but when i take out HOT from the board then it shows ok.
No other component is shorted like this, then i suspect Boosting MOSFET and also changed it. But the result is same. EHT showing good by Blue ring tester. When i remove MOSFET (IRF634A) and disconnect EHT, then i get supply volt ok (55v) along with other voltages and not protected. When i connect the MOSFET without connecting EHT then protected again. I have also tested by series lamp 60w with EHT but it is protected again. There is no leakage in EHT between final anode and earth. H-yoke is ok with blue ring tester. Now i suspect EHT, please justify it.
I suspect that the EHT primary winding may have shorted to ground. Try remove the primary winding pin and see if there is still short circuit or not.
There is one question, SMPS is protected when over load or under load or in both condition. From the above situation it appears that it protects in both condition. But when i open the MOSFET and EHT connection, i am getting 55v ok and not protected how?
That means if there is anything shorted in the secondary side (assuming the high voltage section have problem) then the power supply could sense a high current draw and shutdown the oscillator waveform. Without output waveform, power fet will not switch and the power will collapse.
I have checked some (4) diodes which is connected in secondary of EHT, showing about 1500 in digital multimeter diode testing mode. I have never seen like this, i have always found about 500 in this range. What type of diode is this.
What is the part number of the 4 diodes? I need to check the spec first. Usually they are the Ultra fast recovery diode.
I’m mr. salvador blanco from Philippines and your new aspiring lcd student because i bought your LCD monitor repair last month thru internet.
Nice to know you and thanks for the support.
Actually i own a small rental computer business in our province and i’m tired of bringing my monitor and lcd to different technician but only to find out that the damaged was fixed temporarily and later after one month the same trouble arise again.
I write this letter because i am starting to buy those simple tool and test equipment. i bought a new digital tester and planing to buy analog tester this week. what i want to ask you is the variable dc regulated power supply with this specs.
Output voltage: 0 – 15V DC
* Output current: continuous: 1A
* Output current limit: 1A Max
* Ripple and noise: <1mV (RMS)
* Line regulation: 15mV
* Load regulation: 0 to 100% load: 10mV
* Power source: 230V AC/50Hz
* Meters type: analog
* Volt & Amp meter
* Power On LED Indicator
* Adjustable output 0-15V
* Dimensions (W x H x D): 4.0″ x 6.5″x 5.5″
* Weight: 1.5kg
Is this specs okey to use in case i can’t find a 5A 30 volts dc regulated power supply (which you are using) here in our province?
thank you very much for reading my e-mail and more power to you and your company.
The spec is too small because some LCD Monitor is using 18 volt. You need to get at least a 4amp 30 volt dc regulated power supply.
thanks a lot for your respond…well..i got the book by instant acces download link after he made a payment for me….
so far i think book is pretty much helpfull…i like the simple way you present the possible issues and how to diagnose it…i know you have a money back guarantee but i believe how you will never experience such thing as giving money back since book is really helpful..
You are right!
.you really made some great effort to writte all that down and gather most of useful informations at one place…
That’s lots of hard work that i have out in.
anyway…as your new listed client , i wish to use this oportunity to ask you one thing i have on my desk for last 5 days and i cant figure out the problem…
i have bought cheap some AG Neovo F-417 17″ LCD…funny thing is, LCD turns on EVERY time i turn it on…and it works well for like 10…15…30 minutes…depends…and then sudenly it goes off by itself…then i just click power on button again and it runs back normally and works again for like another 10 minutes…and up to 30 (it has no cycling loop rule of when it will be turned off back again…its random, but between 10 and 30 minutes)….i checked logic board, A/D video board and it works fine…so, all that can be is power supply board i guess…otherwise why it would turn off by itself?
in attachment i send you picture with close up view of board…please…can you give me at least some tip / hint of what to check?
btw, i checked capacitors, they are in great condition…ESR and cap as well…and they are not overheating at all…and there is no any cold solder (cold joints)thanks a lot for any of yout helpful hints…
When you said goes off by itself- the display or the power? If the display goes off then you may need to check on the backlight. If one of the backlight have problem the display will shutdown. If the power went off you need to check if there is still any output voltages or not. If no output then check the primary side. If there are output voltages then the MCU in the mainboard could be the problem because the power LED signal is coming from the MCU.
Yours Yibarek A
Hello, Jestine Yong. How Are You? I have a desktop computer’s power supplmodel #ps-7171-1cf1 s/n 01880696 led no lit, no power I have ac supply voltage in the diode bridge 118volts but in the filter capacitor positive pin only 97 volts dc (red positive pin and black probe negative pin of the same filter(primary hot ground) I took the filter out and measured with a in-circuit DCR ESR analyzer 88A and test ok,I also check diode bridge ok, too. This happen by Electrical company surge power failure for two minutes. If you have any idea about the solution please let me know about it thanks Jestine.
I’m fine thank you. Try check the connection between the filter cap to the bridge to see if there is any component or circuit track have bad connection.
samtron 45bn monitor and the chassis no is bh41-000527a DA14/15L.
problem is IRF630(Q504) is short.i changed new one again it get short.i switched on the monitor power on for 2 secns then it gets off.Q504 is short again.HOT is OK i removed LOT and tested still same result.i tested Q502,Q503 all OK.i changed STV7779.still same result.(Q504 short frequently)
12v ok,instead of 53 v Q504 receives 69 v. explain me detaily why IRF 630 short-circuited.
Try these links:
i need some advice from you regarding my TV CRT brand sony.
problem: No display and no power
1. found cement resistor 3.3 ohm 10 watt open – replace new resistor but have some short circuit fuse blow.
2. suspect fuse blow maybe bridge rectifier short – replace new bridge rectifier but still have short circuit fuse blow.
3. do measure at bridge rectifier line -ve found have continuity between -ve bridge rectifier and cement resistor to ground. when i open the cement resistor from the board no short circuit happen but when i solder back short circuit happen.
i already replace component that i suspect short circuit such as bridge rectifier, capacitor, cement resistor all component is high voltage component but still short circuit and fuse blow happen.
hope you can give technical advice for my problem…
Focus on the semiconductor like power ic and power fet. Sometimes a bad posistor also could cause the fuse to blow.
i have avr with 8 ohms and my speaker is 6 ohms. can i convert my speaker to 8 ohms?
There is nothing you can do to change the impedance of a speaker. It is what it is.
Hello Sir, It has been quite a while we mailed each other. How is work over there? I realy do hope that things are moving fine with you there.
Fine thank you and busy with the repair course.
Sir, sorry to disturb you but I encountered a problem recently that I urgently require your professional assistance. I have this 32″ Goodmans LCD that is giving me power problem. Whenever it is powered on and it worked for some time may be an hour or so it goes off but the standby light will still be on then you put it on again it goes off after an hour or thereabout. I have changed the filter capacitor with the same type I removed from the panel i.e 400V 150uf.
You need to check if all the output voltages are good. Place your meter to one of the output and monitor it and see if the reading will slowly go up according to time. If yes then the power section may have problem. If you have a freezer or coolant and spray it to the power section and see if there is any effect on the output voltages.
Hi Jestine, how are you. i know you must be very busy this year, but i want to ask you picture at the bottom, upper part blank. is it the vertical section problem.
i hope you could reply soon. tq
Yes. make sure check the supply voltage and test all the resistor with digital multimeter. Pay special attention on low ohm resistors.
Thank you very much sir for your solution. I just got your mail now. I have already fixed it. Though I did not do anything serious, I only re soldered all the capacitors and the power transistors and it has been working since yesterday. I really feel honored to know that I have somebody like you out there who can always help us out in terms of difficulty.
By adding the mica it long runs at low resolution but at 1024×768 resolution it runs for about 10 minutes after that it becomes dead i.e. over heated HOT. Then after half an hour gap it can be started again, so where may be the problem.
I suggest that you replace the HOT and check capacitors (non polar) in the s-correction circuit. The s-correction circuit have fet and usually located under the horizontal yoke coil connector. If there is no bad component, try direct replace the h/v oscillator and retest.
hope you are fine.I have a problem to change a data cable of a COMPAC LCD.Its orignal cable conecter to CPU is a DVI concter.I had its DVI to VGA converting adopter but I had lost it and it is not avalible in my country.I want to replace the compleate cable.The other side of the cable is directly conected to an IC [SIL801CT100] on main PCB .I had tried many times to get the PDF of [SIL801CT100] but failed.Please help me to conect the R G B and Vsync, Hsync of a normel VGA cable to IC [SIL801CT100]. Praieng for your good helth.
The best i could get for you is from the link below:
I am working on slots machine monitor model #jd199fa and type J91bm I don`t know the manufacture but there is a sticker on the tube with chunghwa as the manufature but not sure if the board was made by them or not. The color went red on the screen please tell me were to look when having this problem.
The best you can do is to compare the voltages/signals between the red and the blue/green circuit. Any differences are the clue for you to start troubleshooting from the point.
It is my pleasure to tell u that i am developing well in testing electronic components but still not well mastering. Now i feel strong cause i know the right way to test components and i feel like there is some one beside me. Thank u and prepare to here so much from me because the movie is about to biggin.
Now i am about to start with SMPS Troubleshooting and Repearing.
I will be in touch with u by any means.
I have a problem with my Sony Trinitron TV (model KV 2197M5). In between the area as per the attached pdf I have drawn
When I switch on the power, the fuse blows then I have removed bridge rectifier (not to forward the power beyond) and connected the Ac plug again but situation is same.
Then I understood issue is before the rectifier.
When I have removed the part as I have circled in RED, fuse will not blow and I have replaced a new part but fuse blows again. This 3 pin unit is for degaussing coil.Conclusion is no A/c power reached to bridge rectifier when that part (circled in RED) is connected to circuit board.
Appreciate if you can give me an answer to solve this matter.
Thank you very much!
That part is posistor and you need to replace with original part. Check also for the degaussing coil as a shorted coil could cause the fuse to blow. Make sure the insulation tape of the degauss coil did not the picture tube frame.
currently I am
reparing Philips LCD monitor Model ID: 170S6FB/00
Serial number: BZ000542563048
This LCD monitor came with Flickering Display.
I opened it up and on the Inverter board Model: EADP-43AF A I found
bulged 220UF 25V X2, 470UF 25V x3 I replaced them switched on the LCD
monitor and it is still flickering, do you perhaps know what I may
have left out component to replace to fix this flickering LCD monitor?
I was 100% sure that having replaced the bulged capacitors I have
sorted out the flickering but frustrated when the flickering is still
If you have the ESR meter you can check if other ecaps are good or bad. If you do not have the ESR meter try replace all the e-caps in the secondary side. Make sure all the secondary side output voltages are good and stable. Sometimes a weak backlight may cause flickering too.
Dear Mr Yong,
Thanks for my reports which have helped a lot to grow in the repair field.
The issue I want you to advise me is about an inverter/battery charger. It was
brown by power but on checking I fount two brown FET FQP65n06 but these are not
on the market here they have FQP60n06 my question is will it work if i put
Check for dry joints in the crt board.
i have a sony tv model 2192 after turning it on the color of tv is ok but arter one houre the color will be dark or one of the three main color(for example green or yellow) will be more than other colors so could you guide me where is the fault?
How are you and How is your research in electronics going on. I am now really feeling free to open and test both Monitor and SMPS of the computer system and able to test the components through your easy testing techniques. Once agaainThanks a Lot.
Jestine I found a 5 Leg STR in HP s7540 CRT Monitor bearing product code as G5643B. Will you please guide me the Procedure to test it for Short and Open.
Waiting for earlier reply in this regards,
IC can’t be accurately test with meter if it is shorted or open because inside of the ic have just too many components in it. Many times even though the ic was tested good using ohm range ( by comparison method) the ic still can’t be used.
HI JESTINE SIR,
KINDELY CAN YOU TEL ME ABOUT LAPTOP VGA CHIP FIXING EQUPMENT.THERE IS ANY SPECIAL HOT GUN OR LEASER SYSTEM.OR SOME THING ELES.PLEASE HELP ME ABOUT THIS . IF YOU HEAVE TEL ME THE PRICE AND PROCEJUR.I AM IN SAUDI ARABIA.
Usually the repair tech use BGA rework station and you can visit this website to enquire about the price: