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Electronic Repair Questions/Answers & Testimonials- Part 42

By on October 24, 2009

Jestine,

Good Day to you… I just bought your one of your great and very helpfull books last month, “How To Test Electronics Component” and with some Bonus books. Since I don’t have any credit and visa card you may not find my names in your registrations, I just ask my friend Shawn Mhaller (Technical Supervisor), to use his card to be able for me to buy this E-Book. I enjoy reading this very informative books with complete colored illustrations/drawings.

I am planning to buy more books that pertains in repairing LCD and Plasma TV Monitor. Thank you again and more power to you.

Best Regards,

Clodualdo Enaborre
(Electronic Engineer)
Norwegian Cruise Line
Manila, Philppines

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greetings!!! Mr. J. Yong..once again thank you for kind and very helpful for sharing some knowledge….your one of my biggest “IDOL” …..your amazing….your the man… i salute you sir….advance Merry X’mas to you sir and your family circle…

b’ regards,

ricky

 

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Hi Jesting Yong,

I would like to express my gratitude  for sending me the October repair  newsletter  about understanding transistor functions in electronic circuit.I’m really glad because you always send me a valuable information about electronic repair tips.Actually,I have no practical education about  lcd monitor repairing  but due to your monthly newsletter i started to learn more about electronics component and repair .Again , thank you very Mr. Yong for your support and may the God Almighty blessed you  more and more  for your kindness.Hope you can send me more issues next month.
All the best to you!

Respectfully Yours ,
Christian Jayson R. Sabacco
Lucena City
,Philippines

 

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Hi Justine
My DIDIVEIW monitor recently stop working,when power is switched on the power light would blink on and off with a ticking sound.i checked my HOT transistor and many other resistor and components and nothing found to be unsual.i decide to change ic TDA4858 and replace it with ic TDA4856,then power on back monitor.the power led stays on and there is no ticking sound but there is no display.can that be my flyback is damage?

 

Hi Thelston,

Possible flyback problem. Please visit this link;

http://www.electronicrepairguide.com/testing-flyback-transformer.html

jestine
http://www.JestineYong.com

 

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Hi Ducote,

Thanks I got it, looks great,have a question: Working on a Hanns g
HX192D no display but there is the “no signal display” on screen
I have 12vdc & 5vdc coming off of power board but no 3-4vdc for “On”
power it looks like the start circuit is under the power board but canT
tell because the inverter chip is not obvious. There is an MP1038EY it
is a full bridege CCFL controler & two SPK83 8 pin DIP Is this the start
up circuit or would the start up circuit be on the main board?
The main board & power board is connected by a 8 pin stacked connector.

If there is no On signal from the Mainboard then confirmed the mainboard MCU have problem. The On signal need to be present first to the start up circuit. In some newer LCD Monitor the start up circuit already built into the inverter ic.

Jestine
http://www.JestineYong.com

 

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Hi Sir Jestine, Good day to you.! I have a problem with AOC 17″ CRT monitor which I find hard to figure out the problem. The monitor is dead/ no display when it was sent to me for repair, when I tested it I found Horizontal Output Transistor C5521 defective. Checking further for some defective components around Horizontal circuits, I found nothing.  I replaced the defective C5521, but after about 5 minutes of normal operations, the C5521 got busted again. Now I have new C5521 on the monitor, and I observe that it gradually become hot from the start of switch on, so I have to switch off..then on again. May I ask what causes the slow busting of C5521? Thanks to you ang more power.. Eliezer

 

HI Eliezer,

Try this link:

https://www.jestineyong.com/?p=839

Jestine

 

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Hello to Jestine Yong thank you for the information you have sent to me much appreciated brilliant info.

Regards

 

Arron Murphy

 

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I just received a defective Samsung SyncMaster 932B PLUS LCD monitor. This monitor has two lamps. When the power is switched “on”, only one of the two lamps lights up for a few seconds and then go off. Only the lamps (or the remaining lamp) are (is) going off. The power is still “on” because
I still can see a very darkened image. I will call this problem the “power-on-with-no-display” problem.

So, correct me if I’m wrong, but the first test I whish to execute is to see if after the lamp(s) shutdown, there is still power going into the
inverter. To test this, I whish to execute a voltage testing on the 13 volts line (between the SMPS and the inverter – see the attached image 1).
Is this a logical test choice as the first attempt to troubleshoot the problem?

Yes you are absolutely correct! Make sure also the supply DC voltage is entering the VCC pin of the inverter IC even after shutdown. Without this voltage, it suggest that the problem could be in the mainboard or a broken pico fuse.

If it’s a logical test to do, problem is, this will be my first voltage testing on a live circuit board. So, I have a few questions.

1) Do I need an isolation transformer to execute this voltage test?

Generally you need to protect youself just in case if any short circuit. I highly recommends one. However if you have the confident you may go ahead to test it.


2) a. Is my probes location are correct (see the attached image 2)?
b. As you can see (from the attached image 2), I’m not sure what is the best ground position: 1, 2, or 3?

Position 2 and 3 are correct but not in position 1 (because position 1 is positive voltage)

c. Can I use another ground location like a simple metal plate or maybe my anti-static table mat’s ground clip?

The best is to use back the equipment chassis ground.

3) Since I’m testing a line that is on the SMPS secondary side and before the inverter, is the current is still in DC voltage at that point?

Yes it is still in DC voltage

Aside the technical questions, I want to take a few moments to tell you that I just finished reading your book “Testing Electronic Components”
(including all the reports that came with it) and, thanks to you, now I can not only identify most of the components on an IC board but I’m also
able to understand and read more accuratly a schematic diagram. Thanks for sharing your valuable knowledge and skills.

You are welcome and thanks for the support!

I’m a self-employed IT technician, mostly doing residential help desk calls and before reading your book, I would never have taken the chance to
repair a broken CCFL from a laptop or a faulty power supply from an LCD monitor. But now, even if I’m still a very green rookie in this field, I
have at least the knowledge and the confidence to try it.

Yes have made the right choice and if you have any questions please do email me. By the way, more practice will make you good in electronic repair. You may start to build some electronic project kits and this will surely helps you even better in understanding electronics.

Right now, I have just bought your book “LCD Monitor Repair” and all the included reports. I also ordered (from amazon.ca) one of the books you
suggest in “The Art of Success in Electronics Servicing” which is “Basic Electronics” by Bernard Grob.

I like his book and even until now if i need to get some answers about electronics i would still refer to his book.

When I would have finished reading those two books, I whish to be less annoying to you with my tons of questions and be more independent with my repairs.

No please don’t say annoying because my job to help my buyers to become good in electronic repair.

Thanks for your knowledge and for having taken the time to read.

You are welcome!

Jestine
http://www.JestineYong.com

 

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Sir,

I recently bought a Blue ESR meter from you. I finished assembling the unit but I have quite a few questions regarding calibration. During the calibration process where you adjust VR2 to “82” mine reads “82” then changes to “83” is this because of the trim pot. What do you suggest I do to fix it. I am a little bit doubting the readings I am getting with my assembled meter. I hope you can help me thank you and good day.

Raimond

 

Hi Raimond,

Yes, sometimes it will show 83 instead of 82 but that value is acceptable. Try slowly adjust the pot till you get 82 again. For your information a too long probes could affect the reading. Try making the probes in the range of about 30cm and then seeing the result again.

If you have doubt about using that meter, i suggest you get few bad e-caps and a good one to compare the reading. I still could recall the first time i used this meter and have doubt about it too. Now, without this meter, i would not to do repair work because there will be lots of guessing games when checking the e-caps.

If you have other question please do email me again.

Jestine
http://www.JestineYong.com

 

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HI CHRIS,

Message: Hello, I would like to thank you for providing such valuable information to everyone.

You are welcome!

I hope you don’t mind me asking you a question this way…

No problem

I have a SOYO DYLM24D6 LCD monitor which has recently lost all power. I tried to contact SOYO, however they are now bankrupt. I opened the LCD up and the zd1 (I assume this is a zener diode) looks burned. Can you tell me if there is any way to find out the value of a fried zener without a schematic?

Have to get the schematic unless you have the same board for comparison.

The zener diode has no visible part number on it. I have not been able to find a schematic or any info on the power board online. The power board model number is “CGCPOM24EI4” manufactured by Great Wall. Do you know if this is a common power supply used in many other models?

Sorry never come across such model in my workplace.

It appears that the power supply gives out +5v, +12v and +24v. I would consider using a different (possibly external) power supply (brick) if I could find one that gives the correct voltages and amperage, however I don’t see any external power supplies (brick) that give all three voltages +5,+12,+24 – most seem to only output 12v. Thank you for your time and consideration!

You can get a 24 volt DC power supply (with a higher amp)  and then lower it down the value to 5 volt and 12 volt using voltage regulator.

Hope this helps!

Jestine

 

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Hi there or is it shi hao.Anyway,hope God is doing wondaful things in your lives?.You know,i tested a number of ceramic disc and smd caps using an analogue meter turned to 10kohm the meter shows no reading when i tested some of them,some gave a little deflection but does not come back to show discharging..Please help me with some of the charactoristics of this caps(good or bad) when under test with an analogue meter. And hay thanks to you,i now know that bad caps can also blow fuses in power supplies.You deserve a big hug..May you live long..

 

HI Rexford,

Thanks for your email. Some cap which is too small in value may not register any reading from your analogue meter. You need a digital capacitor meter to test it. Yes a bad cap could blow the fuse. Have a good day and thanks!

Jestine

 

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Hello Mr Jestine Yong,
Thanks for your monthly repair newsletter, I now use to go through your website everyday, and thanks for all the good ideas you shared. Jestine I actually want to share one problem hope you can help. Attached is a photo of the problem.

Problem : The RED circle I drawn on it is the place Brightness > exit and save. The thing stuck there and cannot function even I press the buttons on the front Panel that I adjusted.

Thanks.

 

HI Bernard,

You are welcome. That problem could be cause by:

1) a lower supply voltage to eeprom IC

2) Bad data in eeprom ic (need to be reprogrammed)

3) bad MCU.

Hope this helps!

Jestine

 

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HI Bernard,

Thanks for a fast reply, by the way, I am sorry that i can’t know much about the problem anyway Jestine I like to ask a little further on this problem, OK with you?

1) a lower supply voltage to eeprom IC   So what should we check for the lower supply voltage, and which part to check?

Check the supply voltage to EEPROM ic. It can be 1.8 volt, 2.5 volt , 3.3 volt or even 5 volt. It depends on model and you need to test it out.

2) Bad data in eeprom ic (need to be reprogrammed)  So we need to reprogrammed right, so we need a software am I correct?

Yes you need a good data from another working Monitor and a programmer to reprogram it.

Another thing the set is make by BENQ, means to say we must get the BenQ software to reprogrammed it. Is it hard to get it??

You need to get the same exact eeprom IC from a working Benq lcd monitor. It has to be from the same type of board.

  3) bad MCU.  What is MCU stands for?

Microcontroller Unit.

Have a good day!

jestine
http://www.JestineYong.com

 

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Own a Dell XPS M1330. LCD display white vertical 3 inch band. Notebook can o/p to external monitor without any problems. Can repair or replace LCD screen. no:90692540

 

Hi Jeff,

Got to replace LCD panel.

Jestine

 

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Hi Jestine,

 

In my first repair I’ve just get to my neighbor their defective portable 7′ black and white TV “Protech” with model no. PTV5524 for practice in troubleshooting.

The TV problem is what I’ve read from the book and internet forum,  that this is a vertical deflection problem.

I hook up to see the actual screen, there is a black screen from up and down and you can see a small white screen that the picture you can see.

I have test already all the component as I’ve read from your book how to test the component and all are in the range.

I’ve noticed that one of the component is very hot and this is the transistor 2SB834 with heat sink (please see attached picture for your reference).

Is this the cause where the Tv screen squash.

 

Appreciate your kind for the tips in repairing.

 

Regards,

Noel C.

Hi Noel,

Any transistor that run extremely hot then replace it.     Check first the surrounding components especially e-caps and dry joints before you put in the transistor and Turn on again.

Have a good day!

Jestine

 

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HI Spence,

 

 I went to the site that you had on the last email then I went to the sencore link and it said: Sorry but this page isn’t here.

I thought it was my  free report link. Yes you can view the sencore link here:

http://www.scribd.com/doc/2957819/TT204-Identifying-television-SMPS-problems

I would like to learn how to repair my Pioneer DMP-555 DJ Turntable. The fluorescent display went dim and I can’t read what song or track is playing.

Sorry i have not repair such equipment before thus i could not give any expertise advice on this equipment. However, since all equipment use electronic components then you can try to test the components in the set and hope to find out the culprit.

Would your books teach me how to find out which capacitor or item is at fault?

Yes the ebook will teach you how to accurately test out capacitors and many other components.

If you have other question please do email me again.

Jestine
http://www.JestineYong.com

 

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Hi Justin, 

Glad to know your website about electronic repair guide. 

I am now experiencing problem on my Compact HP V500 crt monitor.

After turning on the power supply, I heard a “tick tick tick” sound from the monitor (about a few second),

like a relay connect & disconnect sound, after that the monitor goes dead. It is happen every time I turn off and On the computer. I have checked the relay on the power supply and found to be OK. Do you think it is a playback problem or other component in power supply? 

I look forward to your support. 

Rgds,

Barmen

Hi Barmen,

Try check the flyback transformer:

http://www.electronicrepairguide.com/testing-flyback-transformer.html

Hope this helps!

Jestine
http://www.JestineYong.com

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Hi Raimond,

Can you verify this procedures
Capacitor used for testing (6.3V 3300uf Rubycon MBZ ESR 0.012 Ohms Max)

Sorry i do not have this brand of cap. But according to this chart:

http://members.ozemail.com.au/~bobpar/2003esrchart.txt

it is a good cap.

MCU Initialization procedure
1. press power button to turn on meter
2. short probes then press power to zero meter.
3. remove shorted probe then plug probes to capacitor terminals
**** Capacitor reading 0.01 (which means its working to specification)

The value depends on the cap you want to measure. The above link is the best guide for reference.

Other process
1. press power button to turn on meter
2. plug probes to capacitor terminals
**** ESR reading 0.08 (which means it is defective because it more than twice or thrice it specification)

You have to initialize the meter first before you do the measurement otherwise it will not be accurate.

Have a good day!

Jestine
http://www.JestineYong.com

==============================

Hi Tom,

 

Thanks for responding.

No problem

I was hoping that I didn’t have to remove two caps. I hate to remove a good SMD cap to measure the value, I might damage it. Thought there maybe another way to find it’s value and voltage rating. Looking at the manufacturers code, would you know the manufacturer ?

The 47 16 s is 47 microfard with 16 volt. The 1 50G could be 1 microfarad with 50 Volt. Hope I’m not wrong.

 

The problem with this LCD is that the display would have lots of noise on the screen and double images. As it warms up the issue goes away, and it goes away faster if I applied heat to the general area. Once the display is fully warmed, it works normal. I discovered it by applying a cold source to some of the suspected components and I came upon this e-cap the noise reappeared. Warming the e-cap with my fingers it went away. I have attached two pictures to share with everyone this issue and hopefully it will benefit others. I don’t know if this is the only problem, since I have not replaced the cap.

 

From your description it can be the e-cap itself or corresponding components that need to be checked.

Jestine
http://www.JestineYong.com

 

Hi Jestine,

 

My guesses were 1 mfd or 150 mfd @12 volts. I didn’t think it would be 150 mfd since it was so small. I removed the bad e-cap yesterday and measured the capacitance. It measured .89 mfd. Since I know that the monitor improves as it warms up, thinking the capacitance increases as it warms up, I purchased a 1 mfd, 2.2 mfd, and 4.7 mfd @35V.   I tried a 1 mfd cap, didn’t work. I jumpered a 4.7 mfd an it solved the problem.

 

Thanks for your help.

 

Tom

 

 

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If video s there then G1-80v,G2 +50v,heater 5v..

If in the case of no video.. only heater voltage is there..no g1,g2.

-jim

 

HI Jim,

With video the G2 only 50 volt which is abnormal. You need to increase the voltage by turning the flyback g2 vr. Or something along the G2 line have a cap shorted and you need to direct replace it.

Jestine

 

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Hi Bailing,

Dear Jestine,

Firstly, I congratulate you on your website high ranking. Your website rank here is no two.

Thanks and not bad at number two!

A CRT 15″ monitor came in with the problem of no picture ( with vga connector plugged in ). The display is only dim grey color with something like moire pattern & soft horizontal retrace line. I’ve checked and got:

Green led lit on
Anode voltage 24 KV
G1  -73 V
RGB K  65 V
G2  302 V
Heater  6.6 V
Xtal on MCU has sinus wave, but VCC on MCU is only 4.16 V

Is the VCC on MCU normal? What is the least voltage on it, to operate the MCU normally? I also checked the sec. voltage of this line to be 7.6 V.

What do you think is the problem? What is the different symptoms between MCU fault and Eprom fault?

Sometime, CPU could tolerate such voltage. From your description, if the display if good (have wording) but dim then this suggest a weak tube. What is the brand of the CRT tube?

Jestine

 

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thanks jestine .you’re great ,the newsletter is verry good,and help me repair the electronic equipment faster

 

Toar L.

 

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You are great. Explaining with examples giving detail information! You are outstanding thats why I decided to buy all of your guides, they are worth buying, Hoping to hear from you soon. thank you!

Ismail N

Maldives

 

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Hi Ahmed,

hello sir how r u sir i have a LG studio works 500g(Ref:CB553H) 15″ CRT monitor.whats the problem is when ever we switch on the monitor display comes perfectly,after some time the power indicator blinks in orange color for two times and monitor automatically turned off and again it will turned on and display comes again same process repeats until we disconnect main power.if we kept this monitor aside for 2 days and switch it on again it works perfectly for some time and the same turnoff and turn on problem repeated again with the power indicator blinks 2 times in orange color sir please help me to solve this problem this becomes headache to me sir please help me thanking u sir

I guess your Monitor may have dry joints in the power supply area or bad filter capacitors in the power supply area.

Jestine

 

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Dear Mr Jestine Yong,
I have temperature control unit which uses 5 V
SMPS with 8 Pin DIP IC. There is no way I can get this IC no which
is normally printed on the top as it is burnt.. Circuit is similar to
your TOP 223 P SMPS shown in website at following address.

http://www.electronicrepairguide.com/top223p-ic.html

But there is a 10 kpf Capacitor between Pin 1 & 2 of the DIP IC. I
have tried to use
TOP 223P , 8 Pin DIP keeping the pin no 1 open and TOP 224 Y FET
(with 3 Pin) by correctly connecting the Source , Drain and Gate to
Proper Pins.
Now SMPS works but the out put voltage slowly drops from 5v
to 4.4 volts after about 3-4 minuets time. This may be due to heating
up of the TOP 224 Y .

Will you be able to suggest me part no of the original 8 Pin
DIP IC used .

Thanking you

B.R.Kini

 

Hi Ragunath,

From your description and since the original IC already burnt it will be difficult to get the exact IC part number. The reason for it because this manufacturer came out with lots of IC part number that were used in the power supply design. There is no way we could find the part number just base on the design except to get the schematic diagram.

Jestine.

 

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Dear Yung,
Thanks for the rely,Wile I was going through your May report which is about trouble shooting and repairing Motherboards, I discovered that the motherboard of this LCD am working on is the one in that report which you have labled as SUMSUNG LCD MONITOR MOTHERBOARD. it has the same ADC/SCALAR IC as that in your rpeport.Now whic is the inverter IC you are thalking of?
I have tested most of the fuses labled with 0 on top and they are so far ok.Indicate to me the inverter IC using that board in the May report then I can carry out what you told.Thanks
John

 

Hi John,
The inverter board is joined together with the power board. If you could see 2 to 4 small transformers then that’s the inverter board. behind the inverter board have an IC and i guess it could be that IC. For your information Samsung have many similar Mainboard but different power/inverter board.

Jestine

 

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Hi Jestine

I have a problem here with 2 ATX Power supplies.

Both came in for repair dead (with inflated capacitors), and I replaced all
the Electrolytic capacitors with Panasonic EB and United Chemicon KZE types.

Now they start up, and run fine, but with only a small resistive load (like
a PSU tester).

The PG is good at 1.89VDC, and all +3.3V, +5V, +12V. -12V are all OK.

But when I connect to a motherboard for proper testing, the PSU starts up (I
checked voltages fluctuate, eg. 12V is 11.7-11.9V) and then it shuts down,
and tries to start up again – the cycle continues.

So, somewhere there is a problem with a normal load.

I replaced also the Cosmo K1010 optocoupler, no improvement.

All the TO-220 diodes and MosFets are OK.

Where else should I look to find the problem?

See the attached picture.

Regards
M Yachad

 

HI Yachad,
Sometimes a bad capacitor in the primary side could cause such problem. Guess you may need to test the capacitance value of the non polar cap in the primary side area. If possible solder out one leg of the secondary output diode and test it with an analog meter set to X 10 k ohm. A slight leakage could cause problem. The secondary side PWM IC may also cause similar symptom too.

Jestine
http://www.JestineYong.com

 

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HI Chris,

Thank you very much for the reply and the advice.

You are welcome!

Sorry I’m am just getting back to you,


No problem!

Sir. I am not able to obtain a schematic for the
power board since the manufacturer is bankrupt. They have no contact
info or website anymore. I searched for the schematic and I cannot find
it on any sites that you have posted in your blog.

In fact this is the most difficult partNo information.

Does the manufacturer usually sell schematics for such devices (power
supply boards)?

Usually don’t and those schematics that you could be uploaded by their staff/ex staff.

Great Wall actually made the power board, not Soyo – I
will attempt to get a schematic from them. Even if I can get the value
of the Zener, it’s quite possible some other component made the Zener
burn. Would bad capacitors cause a Zener to burn?

Yes any components that correspond to the zener diode can be a suspect.

I gave them a visual inspection… None were buldging, but I don’t have the special
meter to test them.

If you are serious in electronic repair i suggest that you get those meters to test out bad components.

I have searched on various sites like eBay, Google, and several
electronic part warehouses for the power supply board, but the only
place I have found it is on the Chinese marketplace website
taobao.com. It is a newer version of the board but I think it will
work. I hope I am able to purchase it from the USA.

I heard from a repair friend of mine that taobao.com deals with lots of electronic related products but one has to be careful. You may have sent them money but they will not send you the item

In the event that
I cannot get this board I will consider using an external power supply
to provide the necessary voltages, but for one I don’t know the pinout
for the connector and how the power switch and controls interface with
the power board. The connector pins are not labeled on the PCB. I also
can only guess what current the old (dead) power supply was putting
out. It seems like a difficult job to use a different power supply.
I am very interested in repairing this LCD because it has a beautiful
24″ MVA type panel, and it is expensive to purchase a display of this
size/type.

Guess you may have to try it out. Never try never know.

Have a good day!

Jestine
http://www.JestineYong.com

 

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Hi,  Mr.Yong good morning to you and in your family, can i ask some question regarding my Jvc tv 21″ model no:AV- 21LX ,  the problem is theres a retrace line appearing in the screen even though i adjust the screen control at the flyback to minimum its still appearing.And if you adjust  slowly to higher level it works, it become brighter and at the same time the retrace line as well. Please help me to solve my tv problem.

 

Thanks a lot, God bless always and more power to you,

Dong O. Faller

 

Hi Dong,

Try replace the vertical output ic and retest. If this TV have a G1 pin at CRT board then try to trace from this pin to look for any bad components along the line.

Jestine
http://www.JestineYong.com

 

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Hi Stephane,

 

First, many thanks for being my “personal instructor”. Without you, I would not have the necessary knowledge and confidence to execute all those repairs. I just love to learn new skills and as soon as my ongoing repairs will be done, I will follow your advice and get an electronic project kits. Is there any one better than others?

 

You are welcome. You may visit repair forum as it will help you a lot.

 

Right now, theory (and schematic diagrams) is one thing and practice is another. Even if I have been able to quite easily locate the 13 volts line that supply the inverter on the schematic diagram, now on the IC board, it’s not as easy.

 

Yes one has to practice more.

 

Fortunately, I already start reading your book “LCD Monitor Repair” and in the chapter “Understanding the Start Circuit” (page 44 to 48) you focus the attention on testing the “on/off” pin of the start circuit as the first test to do.

 

Yes that signal is very important.

 

I also learned that this start circuit is right between the power supply and the inverter. COOL! This is great new information that is directly related to the test I first wished to execute; which is to know if there is enough power that goes into the inverter. Now, with this new information learned, I know that I should test the “on/off” signal first and then the 13 volts line directly from the start circuit’s corresponding pin. Thanks for those precious tips!

 

You are welcome!

 

But, on the IC board of the Samsung 932B+ LCD monitor, on the start circuit’s connector, there is no 13 volts pin, only a 5.1 volts and a 15 volts pin (see “Image_3”). So, is this 15 volts pin (from the IC board) is the same as (or related to) the 13 volts line from the schematic diagram (see “Image_1”)?

 

Yes, because not all LCD Monitor have the same voltage. Some could have 12 volt, 14 volt and etc.

 

If the 15 volts pin (from the IC board) is the same as (or related to) the 13 volts line from the schematic diagram, can I test it using its connector’s pin just the same way you demonstrate how to test the “on/off” signal connector’s pin in your book (“LCD Monitor Repair”, chapter “Understanding the Start Circuit”, page 47)?

 

Yes you can.


 

Finally, if the 15 volts pin (from the IC board) is the same as (or related to) the 13 volts line from the schematic diagram and I can test it the same way as the “on/off” signal connector’s pin, then I would have a few questions before proceeding with this test. Because, like I said in my previous message, this will be my first voltage test on a live circuit board and I’m a bit nervous. I DO NOT want to make any more and unnecessary damage to the IC board.

 

Ok

 

Setup

 

Because I had to remove the IC boards (SMPS/Inverter board and AD board) from their metal encasing to be able to access them, I just want to be sure that everything is safe; to prevent any short circuits (see “Image_4” – top view – and “Image_5” – side view).

 

Is the glass plate is a good enough insulator (to prevent any short circuits due to the fact that the IC boards have all their solder joints touching the glass plate)?

 

Yes

 

Test : Ground pin

 

Since the IC boards are not attached to any metal surface, which ground should I use: the power supply connector’s ground pin, the metal clip attached to the LCD panel and frame, or the start circuit’s ground pins (see “Image_6”)?

 

These grounds are all the same. You can test it with continuity test and it should have reading. You can connect to any of these grounds.

 


 

If the start circuit’s ground pins can be used, can I use any of the three pins or should I use a specific pin (see “Image_6”)?

 

 

As long as the circuit board printed the word Gnd then you can use it. Yes you can use that ground.


 

Test : Live pin

 

If I read the IC board information correctly, the start circuit’s “on/off” pin is the first pin at the far left and the 15 volts pin is the second pin from the right (see “Image_6”)?

 

Yes

 

In your book “LCD Monitor Repair”, in the chapter “Understanding the Start Circuit”, on page 45, and in your reply to my last message, you talk about the importance of also testing the VCC pin. According to the Samsung 932B+ LCD monitor schematic diagram of the inverter, there is a VCC line that connects to a VIN pin of the IC (see “Image_7”). Am I reading the schematic diagram correctly?

 

Yes

 

Is the VCC and VIN are the same thing? I mean, is VIN is just another way to label the VCC?

 

Yes, some board even label it as VDD. Is the same

 

If it is, so, the VCC/VIN pin is the fourth pin from the top (on the schematic diagram of “Image_7”) and the fourth pin from the right (on the IC board of “Image_7”)?

 

Yes that’s right!

 

If the VCC/VIN are the same and since the inverter is fed by the 13 or 15 volts line from the power supply, should I expect a 13 or 15 volts entering the VCC/VIN pin?

 

Yes exactly!

 

To test the VCC/VIN pin, what ground should I use: the one from the IC (see “Image_7”), the power supply connector’s ground pin (see “Image_6”), or the metal clip attached to the LCD panel and frame (see “Image_6”)?

 

Any ground but not the ground in the primary power side. Yes you can use either one of the ground above.

 

Finally, about the 15 volts line. I tried to retrace its path from the transformer (see “Image_8”). Is my path correct or am I totally wrong?

 

You are correct. Take this as an example to trace other voltage line. You learn very fast!

 

Thanks for having taken the time to read and to answer all my rookie questions.

 

No problem!

Have a good day!

Jestine
http://www.JestineYong.com

 

==============================

 

Hi Jestine, Is it Electroytic Cap. This time I heated it with a paper of paper so that other components will not be heated too!!.
This morning I put it on the t.v does not come. When heated it, it works first time.
Why is it that the Cap. needs warming up.
I looked at Maplin shop, they have Cap. 450 volt 47 uF. Is it o.k to have a bigger volts. Hope you can tell me this.
Thanks
john

 

Hi John,

The cap could breakdown when under load and yes you can use a higher voltage than original.

Jestine

 

================================

 

 

I am trying hard to find a shop which caters small quantity of solid capacitors and SMT switch for my repairs. Could you provide a link to an online shop? Something like Futurlec but deals more with SMD components.

 

HI john,

Try the list of electronic suppliers here:

https://www.jestineyong.com/?cat=12

Jestine

 

==============================

 

From Joe,

I have just started reading your book, looks v interesing.

Thanks!

I have always been interested in electronics and although I have a basic analog meter that I use to check fuses and continuity I now need a ood one to start testing components.

Yes you need a good one.

Can you recommend a good digital multimeter which is a good all rounder. I am not considering cheap ones but one that will be good for all the tests that a multimeter can do. I read online that there are ones that automatically test resistors, diodes, transistors ect. Do you recommend them?

Get fluke meters. They are very reliable and have features.

As I have just started reading the book, I do not know the required tests, ranges and specifications etc, for a meter so if you can, please recommend some good meters for me to choose one from.

Try this link:


http://www.fluke.nl/comx/show_product.aspx?pid=29983&product=HMA&type=3&locale=myen

Have a good day!

Jestine
http://www.JestineYong.com

 

===============================

 

Hi Le,

Thanks for the free report, it quite good.

You are welcome!

I have an hitachi monitor, it required 12V 5A adaptor, but I only have 12V
780mmA, is this an issue to cause the LCD not working ?
When power on with 12V 780mA adaptor, the power light on then change color from green to
yellow, not thing on the screen.

Yes definitely. The power supply will shutdown and sometimes may even burn.You should get at least a 5 amp and above power supply.

I did open the LCD, they are all SMD
components, all the CAP are SMT CAP only few TH CAP but they are OK,
how can I know these SMT CAP were damage as the TH electronic CAP as
your report.

SMD cap rarely have problem and you can test it using digital capacitance meter or with ESR meter.

Have a good day!

Jestine

==========================

 

 

HI Bernard,

Sorry to trouble you,

No problem!

my tv a Toshiba Boombeat 29″ is down and out,. only see the red light, but power button cannot function it’s blackout on the screen it’s more than 10 years old. Normally when it’s down I restart on the botton the picture will be on, but now it’s not functioning. Mr. Jestine can you let me know what’s the problem before I send it to the TV technician at least I know what’s wrong. Ask one technician he said the cost is more than RM100.00. ask him the fault he say must bring and check. So I need your advice.

Well, it can be anything with this problem. It could be dry joint, bad compoenents or even loose connection. One has to open up the tv and troubleshoot it. Since you could see the red light that’s mean the CPU is receiving voltage. But then again, you still have to test out if the voltages are good or bad from the sub power supply. Try check also if there are any output voltages from the Main SMPS. Have a good day!

Jestine
http://www.JestineYong.com

 

============================

 

 

Hi Bailing,

I had replaced the vertical IC TDA8172, at first powering up the display did change and pressing function keys had a effect, but still not normal ( it’s a pity I didn’t take a photo ). After half a minute the display changed back to the original ( a very dim raster and the function keys didn’t work again ). At this time, the monitor was given a signal by external signal genenator.

Then I changed the signal with a normal computer and taking measurements at the video preamp output, and got 1.85 V. Before by the pattern signal generator it only got 56 mV. Then I looked at the display, it already got a desktop picture but still very dim ( very foggy ) and had a soft retrace line. I pressed the function key and saw it has a recall feature, after selecting and pressing the recall, the display came back to normal ( see the attached photo ). At this time, I checked the VCC supply at CPU and this time it was 4.46V ( originally, it was 4.16V ). Now the monitor is back to normal, but to be honest, I don’t know what was the real problem with this monitor.

Some Monitors even in my side also found to have weird symptoms too. First in your case the function keys do not function then it can function and after the recall feature was selected the monitor came back to normal. I guess you may need to burnt in test few more days before sending it back to customer.

This monitor is a bit strange because it doesn’t have a function to adjust the brightness and contrast. Do you ever see a monitor like this?

No i have not seen this type of Monitor before.

So the user will have to adjust the brightness from the screen pot of the flyback?

No they are not allowed to do so. If EEPROM data corrupted i guess it may cause some missing icons perhaps could be the brightness and contrast.

By the way, I found a label at the neck ( see the photo ), but not sure this label is the brand of the yoke or the entire picture tube?

That’s the brand for the Yoke and not the tube.

Could we check a transistor is normal or broken/leaky, by only taking a voltage measurement at the BE junction?

Yes if you monitor closely that the voltage will not fluctuate. The problem is there is always lots of transistors in a circuit thus monitoring each transistor voltage will take lots of time unless you are very sure the particular section is the cause of the problem.

Because I know when it is in the actvive region it will have about 0.6V. Do you what is the BE voltage when the transistor is in the saturation region? In this monitor I found a transistor registered 1.4V at the BE junction, and checking it out of the board with atlas DCA55, it is normal. What does this 1.4V mean?

0.6 volt means the transistor can be turned on but not fully on (turn on hard). Turn on hard means it has very low resistance (can act like a switch). That means each transistors internal resistance is different and applying different voltages will cause the internal resistance to change accordingly.

And this is the first time that I found the primary winding pins of the FBT is not adjacent to each other but I’m not very sure. Do you think this is normal/true?

I don’t get what do you mean. Could you elaborate?

Have a good day!

Jestine

 

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