Electronic Repair Questions/Answers and Testimonials- Part 46
The time you spent on composing this Article is valuable one. In this New year 2010 i will spend my valuable time in the right way.
Thanks for your news letter, i really proud to be that i an member of your webpage.
wishing you and your team a very happy and prosperous New Year – 2010.
Hello and Merry Christmas to you and your Family..I want to let you know,Im so enjoying reading your books very informative and helpful for me being a Electronic Technician.Ok more power to you and your Company.
Thank you so much. The January newsletter is so encouraging. Your tips are all true and need to fullfill it. Thanks a lot!
Thanks a lot for the newsletter Dec. issue. Doing such troubleshooting works using flowchart can contribute a lot in minimizing the hours to overcome the problems. It was great & brilliant ideas and will be practicing to adopt it the soonest, again Thank You & more,more POWER to You!
Hi i bought test electronic book i am gonna be the best electronic tester,it rocks
Sent from my Nokia phone
Actually I am working in air conditioning and refrigeration services, basically mechanical. So from there I start interested in electronics stuff. Now days the machine control circuit which mostly dealing with was microprocessor and electronics controlled and to have knowledge in electronics is a advance for me. Before knowing electronic components, mostly the pcb circuit board need to send to others repairer and probably just a simple diode mulfunction that cause machine unable to operate and the charges was so expensive just because the machine value is there. Even just a simple relay board yet expensive but have potential to be troubleshoot and just replace some electronic parts by myself and I can get a huge machine to operate back, thats really great fealing. From your ebook which I already gone through so far, its give clearer point of view, new skill and knowlegde, thanks again.
otherthing l have 1 japan LCD monitor , but customer dun have this lcD power adaptor , how to test or know how many voltage for this lcd . (toshiba 15″ LCD model : IPC5016a).
Sometimes there will be spec written at the back of the LCD monitor, from there you will know what is the voltage and ampere for the adapter. Assuming there is no spec written at the back, i guess you may have to take few power adapter to test it out. Try a 12 V with 3 amp then 14 volt with 3 amp and lastly 18 volt with 3 amp to see adapter that can light up the lcd monitor. If you do not have an adapter then I guess you may need to use a DC variable regulator. Turn the voltage till you could see the display and then look at the voltage setting.
Today i got a philips Tv came wit ‘set dead’ problem..I replaced HOT &
Now i can switch on the tv..But smoke coming out from the deflection
coils(picture width decreased).What will be the problem.?Should i need
to change the deflection coil.?
Yes, you got to replace the yoke coil.
Hi Mr. Jestine;
Thanks for the very valuable advices. Finally I was able to fix the “no power issue” it had occurred due to a Bad CAP in the SMPS side. Now monitor is “ON” and works properly. However the “uncontrollable horizontal width” issue still remains same. I found the modulation diode (31DF6) got shorted (leak). Then it was replaced but the problem was not OK.. Dumper diode is good. I can’t see another problem instead of this. (Picture are very clear. ) Tell me.., still can this be occurred due to an issue of the fly back? Or capacitors? what parts need to be checked ?
I guess you need to check along the circuit components that is connected to the 31df diode. Check the pincushion transistor and its corresponding components.
This monitor came with no raster problem but with HV on. After checking the CRT board I found that the screen voltage is 0 and I replaced a ceramic cap 10nF 1kV which had pulled the screen voltage down. Now the display is normal though not too bright, G2 is about 182V.
Now I am checking the G1 voltage when the brightness adjustment is max and min, but this G1 voltage only changes from -99.6 t0 -99.1V, though the brightness of the display does change quite much. Also the KR cathode voltage is only about 1.8V, while the other two KG and KB are 13.8V, but the red color purity is OK. I also check the 3 output voltages of the CRT driver are the same. This CRT board is the smallest which I ever repair and I have used the comparison method to compare the three color circuits, and find it no problem. See the attached photo.
The weird thing is the overall display looks fine only a little bit dim, but the voltage measurements are quite odd. Do you have any experience with this kind of problem and what do you think the problem is?
I forgot to tell you that the flyback doesn’t have a potentio to adjust the screen voltage, there is only focus adjustment can be made. See the attached photo. In this condition, how could we adjust the screen voltage?
This type of CRT have a smaller tube diameter and usually the quality was not that good. The problem could be the tube itself or eeprom data that had run. If the tube is dim, you can try to play around with the resistor value. Trace the resistor value from the CRT board G2 to the circuit before reaching the G2 pin in the flyback transformer. Assuming the G2 resistor value is 1 meg, you can try to put in 1.2 meg, 1.5 meg or even 2.2 meg to see if the situation improve or not. If it still the same, then i guess you may need to replace the tube. Another problem will appear if you replace the tube because we do not have soft jig to tune the tube color. Thus your new tube may have color out problem.
Dear Mr. Jestine
hello from egypt again
I’m Mohamed from Egypt
i hope you still remember me
nowadays, i am working hard to open my small company
i will sell electronic components , repair
electronic pcb and equioment as i have a good experience in that field
also there is a good team with me
i told every one in the field of electronics about you
alot of them want to understand your courses especially in arabic language
please if i want to teach your courses
i mean you will give every student a certificate from you
what do you want me to do?
Thanks and have a great day!
Thanks for the email and the recommendation and yes I remember you. As for the course, i guess you may need to create yourself the course in arabic and give the certificate on your own because our courses do not affiliate to anyone. Similarly my side here where i created the courses on my own and give out the certificate of attendance to participants/students. Have a good day!
Hi Jestine Young,
In my country the electric energy is not constant so yesterday my LCD monitor LG is broken ,I’ve openned and I see the fuse in the power supply board burned,I replace this fuse but when I connect to the power the fuse excplode ,I replace fuse again and explode again.I want to help me about to fix this problem,because I’m remaining without PC help.Please help me find the problem.
With respect Kastriot Marevci.
If the fuse blow again then try to check the bridge rectifier and all the semiconductor components in the power supply section.
I have received your E-Book and find it very simple to understand, Thanks.
You are welcome!
Well I like to ask you one problem Question that is my bomba 29″ TV is now having problem again, this time the red light is on but for a few seconds it’s off and the screen is not lighted.
Check that the sub power supply is still supplying to the CPU even after shutdown. No voltage means you have to check the sub power supply section. It can be bad caps, dry joints and etc.
Another Question is my ceiling remote control fan can I ask how to check with multimeter if the coil is shorted or not.
Coil can’t be check with multimeter. You have to use a coil tester to check it. Multimeter could only check for the continuity but not shorted turns. I have a coil meter that was created to check on the transformer coils. I’m not sure whether it can check on the fan coil or not because i do not have the fan coil.
Thank you very much for the monthly report. I would like to ask you a few questions.
As I been reading the report, I remember about some topics in your blog and reports about the 6.3 volt coming from the board to the crt socket. But I myself cannot pinpoint where is that 6.3 volt cause I have not tried it yet. As what i have seen on the crt socket is the g2 wire, focus, and the ground wire. Could you please give me a picture or explanation about that.
If yours is a CRT Monitor then at the CRT board, there should have R,G,B,H,H-ground,G1,G2 and focus at crt socket pin. Use your meter to test it either one of the pin (assuming you do not know where is the heater pin) and if you got 6.3 Volt dc then that pin is the heater pin. If yours is a CRT TV then you can’t measure the heater voltage because it is a high pulse ac voltage that your meter can’t support.
Another thing, Im repairing a flat iron and cut the one lead of the thermal fuse to confirm the resistance. But it was the power cord is faulty. Even though the fuse is ok, I just replace it with a new one cause resoldering it back, Im afraid that the lead would melt when the iron is extremely hot. Is this true that the led will melt.
Yes, if it too hot it will melt. I guess you need to try it out.
My last question, could you give me a procedure on how to replace a high voltage cable. If it has only a small cut that cause firing on the screen, is it repairable? Thanks and Im eager to wait for your reply.
Cut another high tension cable to cover the small cut and seal it with silicon. Then use a high quality black tape to fully cover it.
I have the followings problems with a Compaq CRT monitor:
– Initially when I switch on the monitor it will respond by making a strange noise…
– Then, I opened it and found out that the input filter capacitor (400WV x 220UF and 850C) was buldge which I replaced with another one (a 450V x 220UF and 850C capacitor).
It should be 85 C and not 850 CELCIUS.
– When I switched on, the lines transformer was perfectly pumping and there was light in the filament but the screen was blank
Any G2 voltage measured at the CRT board? It should have about 250 to 300VDC. No or low voltage means the G2 line have problem.
– I also discover that the LED indicator was showing the green light but couldn’t change to red as usual.
It should be green and not Red. If Red then the CPU may have problem.
I enjoyed your book. However, I now want to understand how to find the
componant that is failing in my Quantum mono 105 ampliphier. I have two
twin mono power amps and one is overheating. (still working but the
transistors are getting hot) I have swaped inputs and no change. I have
swapped transistors and no change.. So I assume that the problem is feeding
the transistors. So my first question is how do I test the current and or
voltage going to the transistor?
Could bad capacitors cause this problem?
Thanks for your email and yes it could be the surrounding caps that give problem. Although this link https://www.jestineyong.com/?p=403 does not relates to amplifier but it will give you some ideas about why transistors get hot.
hello i have a question does your book show you how to test a LMD18245 motor driver chip??
No it does not show you how to test that chip. Generally for every chip, one should test the input voltage, input/output waveform. Missing either the voltage or the waveform means the IC or related components have problem.
I have bought the Blue ESR Meter and Blue Ring Tester I ordered both in assembled form in Anatek Corporation I have ask my sister to buy it for me since she is leaving in the states. The Blue ESR meter seem to be working fine but I have problem with the Blue Ring Tester it seem to be defective when u switch it on all leds on or lit if the probes are shorted all leds when off so I went to the forum site of anatek corporation hoping that there is solution to the problem in the forum there was an advice to make sure that all components are in their correct places which I did so far so good all components are in the right place next advice they said is to examine the copper side of the circuit board with a magnifier and under a strong light looking for any tiny solder whiskers or possibly defective solder joints again which I did everything seems to be ok. I event try to remove the three transistor and the diode one by one hoping that the problem is in this component but everything was ok so I think the problem is in the two IC. Sir Justine I am asking for your kind advice what should I do next since the tester is now with me here in the philippines, I know that u have already sold plenty of this units did u happen to encounter this kind of problem from your customer.
Again thank you for your time Merry Christmas and a Properous New Year to and your family
Yes the most common problem are the ICs, Try replace the IC and retest. The ICs is easily available from any local electronic shops. A good Blue Ring Tester should have 2 LED ON and blinking.
I did Jestine. I had couple of questions that you can please kindly answer- would be great.
1. What is this F101 fuse near the power connector which does not show continuity and burnt out(I believe). There is black mark under it. Round red cylindrical shape.(marked as 1)
If it burnt then you have to replace it.
What are the other components I pointed with numbers 2, 3, 4.
3 is bridge rectifier and 2 and 4 are capacitors
2. Did you see the capacitors which shows pretty busted? Should I replace others not busted?
Sorry i could not see as the photo is quite small.
3. How do I trace the current path? I mean- from power source thru the fuse and then it goes where.
Use voltmeter to trace it as it is more easy then current tracing.
The next connector component is blue cap(?) labeled as TH101 near the yellow component. Please explain. Thank you very very much.
That is a thermistor to protect surge and it should have low resistance reading.
Hi Jjustine, maybe you can point me in the right direction. I’ve got two
Fujitsu Siemens LCD monitors, Scenicview P20-2.
Both with power inverter problems. I replaced capacitors in both screens and
both are working again.
But one of them ended up after 1 day with normal power led, functional
backlight when connected to a computer but without anything on the screen.
When I press the menu button nothing appears on the screen. If I disconnect
the PC then the backlight go off, PC connected the backlights are on.
I’ve checked the fuse on the processor board but that seems to be in order,
it shows 5 volts on both sides.
Also checked the flatcable going to the LCD screen. No problems there
Sometimes after switching the screen on and connected to a PC there are 2 or
three vertical colored lines, switching off and on again make them
thanks in advance,
Thanks for your email. Since you have two identical boards, i guess you have to swap the lcd panel and the mainboard to see the problem. Well, it could be loose connection or even bad contacts in the lcd panel tcp package. the power supply should be no problem since youalready got 5 vdc.
Thanx, i infact looking 4 solution 4 my crt monitor lg (CB563G-NA) it
is in dead rt now, power failure state, ( continues blinking of LED )
let me tell you that i am not profesional technician in fact i am
Physician in medicine, electronic is my hobby, could you help me in
this problem, i need very much detail how to trace the prob.
I removed +B fet but nothing happened, i in primery section i did not
find any ceramic capicitor are faulty but still doubtful should it be
replaced, flyback transformer can u say would be faulty pl. help me.
Try this method:
to separate the board. If the light ok then suspect bad components in the flyback area. If the light bulb did not light then suspect the power supply area.
Dear Mr Jestine,
I have this 15″ crt into my repair shop.First the problem I thought is only the cable data,I replace using other monitor cable and I make a connection. But the problem is my new replacement cable doesn’t have many cables inside it.I mean the original one have about 10 cables, but the new one only have 5 cables, so the other 5 cables I let not connected with any cable.
After I change the cable the monitor can show with good but after about 3 second it blank,and If I turn it off again and turn it on again it shows again.
Can you help me?
Thanks in advance.
A monitor need at least 8 signals RED, red ground,Green, green ground, BLUE, blue ground, Horizontal and vertical signals. However in some newer Monitors, there are additional two signals that you cannot miss. It is the SCL and SDA signal. Missing either one of the signal could cause the Monitor to shutdown. Please refer to this link:
I will just make it little more clear.. I have Envision 22″ with no power problem. I checked the voltage at filter cap and i am getting 164v, so that seems ok…
Yes it is ok.
I checked the voltage at the diode after the transformer and one i get 16.64v dc(seems fine) and on other i am getting 254v dc , with seem way to high… because after reading your ebook i understand that i am suppose to about 5.5v dc or so not 254vdc…
May i know what is the electrolytic capacitor value (filter capacitor) that is connected along the 254vdc line? This line seems to be high.
My question is would that be bad transformer or the bad power fet? or neither?..
I need to know the filter cap value first before i can give suggestion.
Also do all lcd power supply have PWM? because i cant seem to find it on this power supply at all.
Yes, all must have. Some PWM integrated together with power FET in a single IC. Some PWM IC is located behind the power board thus you can’t see it from top.
Dear Jestine Sir,
a CRT monitor RM model no RM550 came to me for repair in dead conditon. the fault was main capacitor and fuse was required to be replaced. after replacing the faulty parts the monitor was ok but a sound like “whistle” came from chopper tramformer and B+ voltage level was above 250 volts instead of 50 volts.
Sir kindly help in this regad that what are the possible causes of this fault.
your co-operation will be solicited, please.
Try replace the Power IC and retest, if it still have problem then i guess you need to check all components in the primary side.
First I want to thank you for the great efforts you made on the web to support electronic repair business.
You are welcome!
We involved in the field of computer hardware repair including display monitors since 5 years and we are going to expand our business by opening a new service center for computer monitors only, so we want to know your opinion about the advanced devices for troubleshooting that we need to make the diagnostic operations go faster. you know we use the traditional ways in troubleshooting (visual inspection and multimeter only)which take long time and not completely accurate.
Are blue ring tester & blue esr Meter enough for starting an advanced monitors repair center?
Yes, they are good tester and i have to use them always!.
Get also high voltage probe (for crt monitor), digital capacitance meter, and oscilloscope.
what is your opinion about (HA325 Horizontal Output & Flyback Tester) from Sencore Company
I have not use this tester before thus i can’t give any comment about it. We did not buy this tester was because, by using the other test equipment, we could also solve the horizontal problem.
is there a universal tester for LCD monitors?
No, the equipment used for repairing CRT monitor can be use to repair LCD Monitor.
Sorry for my long message but We Urgently need your opinion as you are a very experienced person in this field.
Have a good day!
i am going to make one of these isolation transformers but i have some questions if you answer me i will be thankful
refer to page 98 smps book your new book the panel of transformer shows one volt meter range up to 500 v
and 1 ampermeter range up to 1 amper
my question is is really require to put voltmeter with this range 500 v ? and amper meter up to 10 amp and what is the usefulness of these two?
No, in fact you don’t need to put the volt and amp meter. I put it just to let the students see the volt and ampere.
and or i can get smaller one ?
Yes you can but it is not necessary.
i could not found such transformer ready to use anywhere in my town?
Mine was a customized transformer. In fact you have to ask those people who make the transformer to make one for you. It is not easy to get this type of transformer even in my place.
I was wondering if you have any trouble shooting manuals specifically on capacitors. I see a lot of swollen caps and would like to learn more ways to check all types of caps mainly in circuit.
If it is swollen then directly replace it and retest the set. If it is not swollen then you may need BLUE ESR meter to check it.
Hope u enjoyed Christmas celebrations..
Why in most of BENQ LCD monitors, the transistor C5707 getting short ? while replacing this transistor, we should also replace the tuning capacitors??
Because is the cap problem that had caused the c5707 to go shorted.
what does the specification .15J100 mean?
.15 uf 100 Volt.
what are the major voltages which should be present at the mainboard connectors(from power board)??
Depends on design. 12v, 5 volt are common voltages.
A black diode like component is the Picofuse in Benq LCD’s?
Advance New Year wishes..
I have a LG 700E.
Its display has dimmed. however when I tap it sometimes it becomes normal.
I tried to open the cover and see any loose contact or so. I unclamped from bottom side but unable to release from the top side of the monitor.
Can you pl guide me.
You have to poke the top part with a flat hard metal so that you can open it. Once opened, check the CRT board fro dry joints.
I have a Phillips 55 inch HDTV and when I turn it on, there is no picture, no sound and I can hear something steadily chirping on the circuit board. Can you tell me what is wrong with it?
There might be something shorted. Guess you need to open the tv and check for bad filter cap or even bad output diodes or transistors.
HI MR.JUSTINE YONG.MAY U LONG LIVE,
I HAVE A PROBLEM WITH MY ACER “AL1917ASM” LCD MONITOR.THAT THE SCREEN GOES BLACK FOR 2 OR 3 SECONDS AND THE MESSAGE “AUTO CONFIG PLEASE WAIT” IS SHOWING ON THE SCREEN.I THINK IT HAPPENS WHEN ANY INDUCTIVE ELECTRICAL APPLIANCE SWITCHES ON OR OFF.
CAN YOU HELP ME TO TELL ME HOW CAN I SOLVE THIS PROBLEM WHILE I AM NOT A PROFESSIONAL ELECTRONICS TECHNICIAN BUT I HAVE SOME EXPERIENCE OF ELECTRONICS REPAIR. THANKS IN ADVANCE.
It seems like your case could be the problem of Mainboard. It may be the corrupted MCU data.