good day to you Mr. Jestine.thanks a lot for the june repair newsletter.by the way my daughter gave me her old laptop,an LG(IBM) which has some problem and she cannot use that is why she gave it to me to fix what problem it may have.luckily i got an original OS of winxp from one of my friends and i formatted it totally to get rid of the virus in which some of my flash drive that i used was also damaged when i used this laptop before i decided to reformat.
to make the story short,it works well but after few weeks the said laptop becomes intermittent.when i press the middle part of motherboard,screen display will be ok,once i depress screen will be black.i tried also using external monitor to see if the monitor is at fault but also no display on the external monitor so i assume the problem is in the MOBO.
i’m planning to put the mobo inside the oven (275 oC)to do what they call reflowing to fix some solder joints,sort of crack or cold solder.this is my last option but before i proceed please give some advice on this matter if this is recommended or a do or die move.i’ve tried to locate the loose connection every inch of the motherboard with several type of magnifying glass but the components are too small to be seen by the naked eye.
thank you in advance.more power to you and your family.GOD BLESS!
Intermittent no display is usually caused by dry contact in the vga graphic ic. Try reflow those big ICs in the Mobo before place it inside oven.
Hello again.. Hope you can help me with these tv problem am facing with.
25 ” Colored Tv…. before the problems is ..the pictures is with shades moving. i have check some capacitors ,,upon pressing those connection sometimes gone but sometimes coming back…. several opening then i dont really knew what happened next is no sound no video already. I CAN ONLY HEARED THE RELAY CLICKING AND THE LED LIGHT IS ON AND OFF ONLY.
21″ Colored Tv… The problems is before i have turn ON the pictures is. ok ..then after 5 – 10minutes turn off all and cannot on already… I have check the Transistor D1555 from base to emitter is shorted? both positive and negative prove tester analog is going right 0 or shorted. pls note that upon soldering all the cold solder the tv appeared with white lines horizontal without any sounds…meaning the TV has power already but only lines.
I just hope you could give me tips for these.
For both Tvs,
The first section to check is
1) is all the output voltages from the power supply good and stable?
2) If it is good then did the eeprom and the CPU getting 5 volt?
3) If yes, then is the B+ voltage to the flyback normal?
4) If yes then is there a pulse to the base of the HOT?
A TV or monitor should have a good B+ voltage and pulse to the base of HOT in order to produce the high voltage. missing either one will cause no high voltage symptom.
Relay clicking can be cause by the CPU sending a pulse signal (instead of on signal) to the driver transistor that drives the relay. You need to check or replace the cpu.
As for the white horizontal line you need to make sure there is a good supply voltage to the vertical IC. If the supply is good the you need to replace the vertical ic and retest.
Thanks sir, but i dont have a service manual. Secondly ihave another problem with a sanyo crt television the problem is that the picture will not appair even you turn the bratinees and contrast but if you adjust the colour the picture will appair vary drak on the screen with over colour, when you increase the g2 voltage the retrance line will appair. Sir what is the solution to this problem. I have test the g2 voltage it was 329v also their is a light on the neck of picture tube. Thanks for your concern.
This seems to be the problem of a bad picture tube.
Jestine ! I am collecting ebooks… this one is one I want for shore… Thank’s for informing me!
It’s always a nice incoming when I see Jestine Yong in my inbox… Always welcome!
Success and Happyness to you my friend !!!
All the best…
how to check non polar capacitor. how much it important in circuit.Till i have not get esr meter
You can use a digital capacitance meter. It is quite important because non polar caps could cause problem in circuit board.
Picture getting very dark in and out.
What you think?
Try press the osd menu. Is the menu also dark in and out? Check also if there is any bad e-caps in the power supply. Just make sure the output voltages from the power supply are good and stable.
Sir,in the month and years that have gone by,I was so very much impress with all the newsletter that you’ve been sending to me..it was indeed so informative and very concise base on its picture,literature and other informative representation of your. .. Electronics Repair. Sir,I do hereby sending you my sincerest thanks to you and in behalf to all your staffs involved in helping hand in hands make this come true. Thank you so much..Sir,Jestine Yong!! More Power!!!!! Armando Yu
Sorry for the late reply. You’re right just know I removed the power IC, measuring the VCC pin supply got 23.97V. ( rise back to normal ) and then I checked the removed power IC with the 3842 power IC tester, the led diode still lit. Were those 2 power IC ( one was original, the other was a new one ) all bad? Why were those two power IC when being checked with power IC tester, the led diode still lit ( still showing good result )? I’m very confused now.
What is the next step then? Do I have to replace the power IC again?
Try replace and retest. Check the surrounding components of the power ic to see if there is any .1uf cap and test it with analogue meter set to x 10 k ohm. It should not have low reading. Try direct replace the run DC diode and the filter cap as sometimes the run dc diode could break down. By the way could you take a photo of this power section.
This is a another local brand CRT monitor which I found its C-Coil ( in series with H. DY) checked with blue ring tester was no led lit, its inductance checked by Atlas LCR meter was 4.2 microHenry. What is the usual led indicator of this C-Coil tested with blue ring tester usually showing ? If a coil is shorted, does its inductance value changed? What is the effect of using junk monitor C-Coil which doesn’t have the same inductance value?
That should be a linearity coil and under blue ring tester have no reading. This coil don’t give problem. If you use the wrong type of linearity coil the display either right or left side will squeeze inward (smaller width compare to the other side.) What was the complaint of the monitor?
i have sanyo tv when i plugged in then the fuse and WF051-UF16 switch power transformer/ will heat up and after smoke burned what i do help me about that problem.
If the power transformer heats up then the primary winding could have been shorted and you need a replacement. Before the replacement make sure all the components in the primary are check good.
I have a problem regarding LCD TV claiming under warranty & I am not sure whether I should contact you or Kent Liew. I need professional consultation or witness in a consumer tribunal court regarding a damaged LCD screen claim. Allow me to briefly describle what is the issue about. My relative bought a Panasonic LCD TV Model: TH-L42U30K & in a about 1 month the LCD screen was discovered cracked when the power was switch on. The LCD TV was not subject to any external forces & there is no physical damaged or mark on the screen. To my knowledge LCD panel can crack by itself for quite a number of reasons apart from the external force on the screen. Panasonic claimed that the damaged is caused by external forces on the screen . They will charge labour & LCD screen replacement.
We just finished the first round of the tribunal court in Ipoh on the 18 June 2012 & the outcome is that the judge want us to get somebody expert & supporting documentation in this areas to represent us in the tribunal court to support our claim.
Do you provide this type of service ? If yes, what is the price? The next tribunal court hearing is schedule to be about 3 weeks from now.
Hope to hear from you soon. Thanks for your time.
Sorry I don’t provide this kind of service because I’m no expert in manufacturing LCD panel. Take a look at this link:
|Good Day sir,
Could you please help me how to solve this problem,its about a crt tv Tusunra model NE-1436 that has a word ”FACTORY” in the top portion of the screen,and a red lock in the left buttom corner.i cant find a manual for this unit,.is there any option sir to solve this?thank you in advance,and more power!
If there is no stuck button then problem could be the factory setting and you really need the service manual to enter the service mode. Sorry i do not carry any service manual and you may need to try out eserviceinfo.com
55.8V DC whatever is the resolution. Just know I checked the signal entering into the gate with scope, it is a square wave with plus and minus peak voltage.
In this case try replace the h/v oscillator ic. Check also the holdown/safety capacitor nearby flyback because if the cap value run it could also affect the width.
By the way, do you know the meaning of pink marking 1H, 1V, 1B at the wafeform of the attached schematic diagram?
Sorry i do not know the meaning but the width of 1H, 1V,1B represent time (period). This could be the manufacturer purposely label it differently so that you will know which waveform to refer.
The display is still small. I’d say my repair successful rate for CRT monitor is only about 70%, and I think that is caused by my lack of its theory /working principle. Where can I find its working principle knowledge?
Actually I could not find the working principle either. It was all based on the schematic and trial on error. Removed components in working monitors and see the problem. And also have repaired many monitors that have added to my knowledge.
Another is a question about the voltage marking at the pins of a flyback, please see the attached photo ( from another CRT monitor ). Do you think -12V, 87V etc is the direct reading of a voltage measurements at those pins? or we have to trace to some other pins?
Those values is after the ac voltage conversion. That means those voltages are DC voltage. You cannot check that ac voltage with your normal multimeter because it is a high pulse frequencies and you need to check it after it has went passing through a diode.
I got it at last –THANK YOU VERY MUCH!
I am currently trying to repair a PHILIPS DVD HOME THEATRE SYSTEM HTS 3010 component.
I removed the SMPS which had a few burned caps (close to the Power fet and opto isolator IC’s).The DUAL rectifier (Comm Cathode) was also shorted (replaced with 2 single diodes)
My question :Can this SMPS be tested without load for the correct voltages?According to the PCB (top to bottm) :23V – G – -27 and 5V – GND – 12V – GND – BK5 and GND – AC1 – AC2 – GND – -27 – BK5 – ON/OFF
Should these voltages measure correct before I connect with the main board?
I have not repair that model before but usually when repairing smps it is require to test it with the mainboard because some smps will shutdown if the load is not connected.
I used to work in industrial electronic repairs for a company in the UK. Although i really enjoyed electronic repairs, the money was very low. The job was very interesting with a great deal of variety, and there was so much to learn, but the financial rewards were very poor. I now work in a boring job fixing trains down to unit level with virtually no electronics involvement at all. The problem is I am earning twice the money i did when i was working in electronic repairs.
My question is, do you think there is any money to be made from electronic repairs anymore. With the extensive use of SMD devices, it has become more difficult to repair electronic consumer goods and most people just tend to replace these items now. What do you think?
I enjoy reading your articles and will continue to keep an interest in electronics, so keep up the good work please.
Good question. It depends on what type of equipment you are repairing. If you repair those low value equipment the returns will be low and vice versa. The current trend now is repairing LCD TV, PLASMA TV, LCD Monitors and laptops. Not only you need to be good in electronics repair you also need a good marketing skill. Those repair techs that have good repair skills and marketing they tend to make more moneys than those who just wait for items to be sent to their repair shop.
Hope this helps.
Please, i want to confirm something from you.
1. if i see voltage at the legs of the primary power transformer.i hope it means the power ic and power fet is functioning?
No not really. A bad power ic will still have good supply in but no output waveform.
2. if there is voltage at the primary power transformer and no voltage at the secondary output diodes,where is the fault likely to be?
It can be shorted secondary diodes, shorted load (mainboard) or bad components in the primary side.
3. 17 inches dell lcd monitor produce hissing sound at the power supply board and the display go off after 30 seconds and the power led remain on.I discovered that the display goes off as a result of the hissing sound which comes from the power board but when i checked the inverter section,the pico fuse is ok and the four small fets are alright and the lamps are ok too.what do you think is causing this hiss sound and display going off after few seconds?
You need to check where is the hissing sound from. From main power transformer or high voltage transformer? Try gentle tap on the two transformer to see if the sound will go off. Make sure also no dry joints in the leg of high voltage transformers. Have you try to use 4 good backlight to confirm the problem.
Hi: I’m having trouble trying to find information on how to test smd ams1117 regulator.Removed 2 from main board but can’t find any useful information on how to test them with a digital meter or mult meter.(grd,V-in, V -out). Any tips on how you do this?
This one is voltage regulator. You need to pump in the voltage in order to measure the output. The ams1117-2.5 means the output is 2.5 volt and ams1117-1.8 means it is 1.8 volt output. The input voltage should be about 5 volt.