hi jestine, thanks for the news letter and i need you to help me i got a crt ctv monitor for repair and it had a burnt out vertical ic but there is 0 voltages at the secondary side of the smps transformer and at the primary side at the main filter there is 280 volts dc and i replaced pwm 3842 and fet power ic pp70zp and checked all diodes and replaced all capacitor,i checked starting resitor 470k and hot 5489 all ok but yet my problem is unsolved can you help me in telling me the solution of my problem thank
I suggest that you follow the link below to isolate the problem because seconday side also can cause no output voltage symptom:
i have two qeastion that i want you to helf me to answer. First sir, what will course the str451 power transistor to get shorted the more you replace it.
Bad quality of the ic and still have bad components in the circuit board.
How are you doing. I hope everything is going well.
I have a question. I recently got a Scooter Power Wheel Charger with a output of 24V, 8.0A. When i’m charging the batteries of the scooter with this charger i get some error codes on the display. The original charger of the scooter has a output of 24V, 4.0A.
Is it possible to reduce the ampere from 8A to 4 or 5A with a some minor adjustments in the power supply circuit. Are there also other ways to do this.
Sorry I’m not into electronics design but the below link could give you some ideas:
that means if the charger could produce 30 to 40 vdc from the secondary output then what you need to do is to buy the above ic and connect as above thus you will get 24 volt with 5 amp.
Hope this helps.
thank you sir. one more thing sir…could you please tell me if the circuit design of LED and LCD monitor are the same?..what is the difference?
The LED lcd did not use inverter board like the normal lcd monitor. They are using driver ic to drive the LEDs.
Hi Jestine Its a dual trace 60 megahertz both beams only show the dot. It also have the component test button which show you the forward and reverse charistics of component under test. timebase adjutable between 50 ms-.05us and volts/div 5v-.01mv and all other normal scope control buttons. I hope this info will be more helpful. best regards Dan
60 Mhz could be good enough together with those spec.It depends on what type of equipment you are repairing. Generally getting a 100mhz will be good because you do not need to upgrade it again.
I have transistor “ DK998 and KTD998-O NPN 120V 10A 80mW can tell me if they are near or not , I found they install KD998 instead of KTd998 ?
Sorry i have no info on these transistors. I guess you may need to try and see if it work or not. But before that make sure no other bad components and if the transistor could work then make sure the transistor is not hot otherwise it can’t be used as substitute.
Good day Jestine.. i have checked 470uf50vdc electrolytic cap.from the secondary transformer.i found out that its leaky.i replaced it.but no respond of the voltage. its still dead set and i checked the 5 pins ic regulator but no mark of value of ic.i measured the voltage from pin num.1 of ic.with 250vdc.all the rest of pin have no voltage to measure.what is the remedy?can you help me how to fix it?God bless Jestine.
If all components check to be good which include the secondary diodes then only choice you have is to direct replace the power ic and retest.
Hello sir . Plz help me out , i have one hitachi tv c2524 . The problem is horizontal output transistor . If i put transistor to it , it will be hot and after few minute it will be shorted .plz help me what can i do?
I suggest that you check on this link:
I hope your having a good day!
I’m fine thank you.
I am attempting to repair an LCD TV with a blinking problem. I’ve found out that the SMPS is the problem. There are 2 outputs coming out of CN801: 13V and 5Vdc.
There are 2 capacitors (1000uF/25V) from the secondary output (13V) that are bulging. This is a sign of over voltage as I have learned from your ebook.
When I checked the output voltage from CN801 using my dmm, I found out that one of the reading is fluctuating between 12.5V and 0.90V. The 5V is just steady. Additionally I have also found a 10Vac output when I am measuring the 13vdc output pins.
So there are 2 problems that the unit has experienced, overvoltage and blinking problem. but I think that the overvoltage came first, thus resulting in power blinking. Please correct me if I am wrong with this.
Since I am also a member of Kent Liew’s TV repair site, I managed to get the Schematics needed for the TV PSU. Unfortunately the schematics provided is very small and blurry when I zoom in the size of the diagram. So I am having a hard time reading it. No component description and values are readable.
What do you think may have caused the problem and which problem shall I do first and how? Your inputs are very welcome.
I suggest that you replace the 2 e-caps and retest because sometime one circuit problem (ripples entering circuits) also could cause other circuit to be malfunctioned.
Sir I need to know (1)the common symptoms of faulty retrace timing caps & yoke series cap,2) the ratings?
Problems can be one vertical line, small vertical width, display curve inward, shutdown and etc and it depends on model too. The rating is usually few hundred volts. If the safety cap (holddown cap) have problem there will be high voltage shutdown and sometimes instantly kill the HOT.
This monitor when powered from cold condition, always has irregular fancy display for only about 5-10 seconds, and then back to normal ( see the photo ). If the set is already on for 3 minutes or above, then turning off and on again, the fancy display won’t come again
What is exactly the problem?
As usual you need to make sure all the output voltages are good and make sure it has h/v signal at the h/v oscillator ic. Make sure also the cpu crystal is good.
Another question is about the component on the lcd screen board, marked on board as TCX or TP34, has a stripe like diode, but I haven’t checked it off board. Do you know what component it is? ( see the photo ).
It could be TCx or other code. Other codes that marked as TC are diode. TP sounds like Test Point. If you get one reading at x 10 k ohm then it is a diode.
Usually what is the rating of the use F1 on the lcd screen board? In this case the fuse marking on its body is FK and burnt.
Usually is 1 or 2 amp
Hello jestine, this Douglas. I just wanna know if you can help me with the problem that we have. because every time a DVD has lost its power, the problem is always the memory. and we have always a hard time in going to manila to buy an I.C. which has a program in it. do you have a DVD programmer that can program a DVD I.C. EN25T80 and a I.C. of 24C01 to 24C08 series. can we order it from you? or can you help me where to order this kind of programmer? I saw one of this programer in manila. but they don’t tell me where they got it. they are charging 200 pesos for every I.C. EN25T80 with program in it. I hope you can help me acquiring this programmer. thank you and god bless you always.
I’m using Pony prog from Lancos.com . It can program the 24cxx chip and not sure about the other chip. I suggest that you visit the website to check the spec and email the owner.
Hope this helps!
Yes. I have already replaced the capacitors mentioned 3 days ago. I measured the secondary output as 12.85V in contrast to 13V which is expected of. Should I still inspect the other components to find out what brings the voltage down, or should I leave as it is? The TV is not showing any signs of deterioration. As far as I see it, its perfectly working again.
Many equipment output voltages have tolerance thus in your case you should leave as it is.
Another thing, what do you think caused the caps to bulge? And yes. It makes sense that ripples coming from one circuit can mess up the whole unit.
Bad quality caps were use and the voltage line higher than the rated voltages of the cap could cause it to bulge.
I would like to take this opportunity to thank you and congratulate you on writing good ebooks that helps us electronics enthusiasts. I’ve finished the Testing Electronic Components book and just half-way on the SMPS Repair book, but I have already learned a lot of techniques and valuable skills from you.
Thanks for the support!
hi good day sir,,,
sir nice to have your time again sir, im here again obviously ask another question,,=)
ahm sir im now working to a new t.v. problem… to be specific its a sharp t.v. set..
it has a power on problem… i tried to plug it then open the said t.v. set but the only thing happen is that, the only two LED power lights is the only thing that works,, it has two LED’s and the other one lights on and off,,,
i tried to open the tv set then plug it in again.. i notice that there is no light inside the picture tube ending attached to the crt socket…
sir.. will you help how to fix this problem.. i already tried to check the capacitors.
thank you sir for your time,,, god bless..=)
First you need to make sure is there any good output voltages from the SMPS? Next make sure there are B+ supply voltage to the flyback and that the HOT base have an input waveform. If the flyback is energized then you can see the light in the picture tube.
Hello Mr.Jestine kalau TV LCD Samsung backgroud colour merah. gambar pixel colour lain tak berapa hidup merah dominal. agak-agak kalau macam tu apa problem ya.?Perhap Mr.Jestine dapat berikan serba sedikit tips kepada saya.
Kemungkinan masalah t-con board ataupun lcd panel.
good day sir,
please send me table guide for ESR reading. and sir did you find LCD made from china are robust and have components available?
please send me table guide for ESR reading.
and sir did you find LCD made from china are robust and have components available?
Usually not robust and hard to find parts.
i live in london england with 240v ac ….could you tell me the best way of turning a 240v step down too 110 transformer ..into a veriable transformer ( IF POSSIBLE) & able to work on plasma tvs please …..or could you tell me a good veriable isolation transformer i could use in london england please….
thank you ..norman
You can use a ready made step down transformer or a variable transformer to tune it to 110 volt. The brand that i known was China made brand. if you could get a brand that is slightly expensive than the China made brand then buy that one.