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Electronic Repair Questions/Answers And Testimonials- Part 47

By Jestine Yong on January 20, 2010

Hi Jestine
Thanks for that information.You have a real heart for your fellow repairers
and hobbiest around the world.Thanks for that and i hope you will continue
to serve them in the years to come.
Thank you
Koniel Day

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Hi Joe,

I have two nec computer monitors that the company that I work for were going to throw away as they were out of order.

I managed to repair one as it only had a blown fuse. But the second one has good fuses so it hs another fault.

I am attaching photos of the power supply so that maybe you can help me identify certain components.

They are numbered 1,2 and 3 in the circuit photo and I have included a closeup photo of them also. Can You tell me what they are?

1 is high voltage transformer, 2 is switch mode transformer and 3 is coil

I also need to check the voltage out from the ten pin out to confirm if the power supply is ok or not. But I cannot understand how to check the voltages . Its got N/F (dont know what NF means), gnd (ground ok) 5v and 12 v. but which pins correspont to what? Can you explain to me how to check the voltages?

N/F is on/off signal. Just place your black probe to the ground (body casing) and red probe to the pins according to the label and you should get 12v, 5 v and the on is about 2 to 5 volt and off is zero volt.

Jestine
http://www.JestineYong.com

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HI Saeed,

what do you mean about “a little bit pressure on the diode”

Press the probes harder on the diode.

and
under load”

Breakdown when under load means the component will have problem when the current flowing across the diode.

and “erratic movement” ?

Means the pointer of the analog meter is not stable and will move to the right/left. It is not constant.

Jestine

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HI Cheema,

Thank you for giving me such a vital information, it is great. I have a HP 19″ LCD model no. w19e, it gives the vertical line having width about 1.5″ on center- left side, as it warms it become (Red, blue,green,black) multi color lines, can you tell me how can i solve it.

This problem is LCD panel fault and you need replacement.

Also i have an HP 22″ LCD model no. w2207, it works normaly, but as i change my computer resolution, or i power the LCD off, its display vanishes, and power on light start blinking. It gives display after a break of 10 minutes. I have Windows XP installed on my computer.Please tell me what,s the problem..

Try check for bad filter caps in the Monitor. If all the output voltages from the SMPS are good then suspect a bad Mainboard.

Jestine
http://www.JestineYong.com

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MORE THING NEED TO KNOW THAT HOW TO CHECK SMD IC BY MULTYMETERE. IS THERE ANY TECHNIQUE TO REMOVE SMD IC BY NORMAL SOLDERING IRION OR HOT AIR GUN.

I AM WAITING FOR YOUR FAVIOURABLE RESPONCE.

THANKS

AKSHAY

HI Akshay,

Thanks for your email. About removing SMD components, i only use rework station as it is faster as compare to using soldering gun. Try find from Youtube as it may have the ways to show you how to remove it. To check SMD IC i rarely use multimeter (except for check the supply voltage), i used oscilloscope to test SMD ICs.

Jestine

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

Hi B,

These days I am working on an old Sony 14″ CRT monitor. It has excessive brightness and retrace line problem. I have confirmed that it should not be a bad CRT, as explained in the http://www.repairfaq.org/REPAIR/F_monfaqa.html

Adjusting screen pot, it does have effect ( 588 to 680 V ), video output supply is also OK ( 200 V as stamped on the CRT board ). I have changed several electrolytic capacitor in the vicinity of the VH synchronization IC ( TDA 2579 ), but the problem still remains.

This monitor is totally weird to me, as its G1 is connected to its frame body ( ground ), the flyback only has 1 anode cable, there is no VGA video input, there is G4 written on the CRT board, etc. Do you think that all these weird things are because this monitor is using an aperture grille ( trinitron ) instead of shadow mask type of picture tube?

It can be that the trinitron picture tube is different.

I am totally lost of wits now, hope you could give me any idea of repairing this type of monitor. Attachments are some of the photos of this monitor.

Your problem could be in the Vertical output ic or corresponding components. Try check the supply voltage to this IC and direct replace and retest.

Jestine

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Thanks Jestine, I alreadly purchased your new book power supply repair guide yesterday. I just randomly read coz im still busy at work. Im sure this will improve more my knowledge in repairing power circuits.
I’m repairing SONY CTV MODEL: KV XG29M50, the problem when i float the Horizontal out transistor collector i can measure 135Volts & standby lit in the power indicator. when i solder back the collector, the voltage drop to 12 volts, can’t start the tv. I already replaced the Flyback transformer & big jungle ic., the problem still the same. Maybe you have idea, kindly help me also. thanks Jestine.

God Bless you always. Happy new year to you & family.

Jerry

HI Jerry,

Thanks for the support on my ebook. Your problem could be in the power supply section or in the high voltage section or even a shorted yoke coil. Try this link to isolate the problem:

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

Pleass update me the status-thanks!

Jestine

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HI Sunny,

How often do you see power IC going bad??

Quite often.

I got a viewsonice monitor problem was flashing green light, so i took it part and found 4 caps were bad.. I replaced them, still the blinking green light, then after like 3mins of or so and it died completly, no light or anything… all the caps are installed right i double made sure… I am getting power to the filter cap, but no power to the Power ic… also the power fet checked out ok with ohm test. I am wondering if the power ic by itself it shorted. Or you think is something else?

It can be the power IC or corresponding components. Always check corresponding components if you found bad Capacitors.

Jestine

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Why is it like a power supply for an LCD is so difficult to fix it that someone must only buy the complete power supply and replace it. And there is this other LCD i have, only the red light comes on but it does not switch the screen, what can be the problem?

HI Paul,

In fact LCD Monitor power supply is easier to fix than a CRT Monitor/TV power supply because it has less components. The red light means the mainboard have problem.

Jestine

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HI Bailing,

Yesterday, I forgot to thank you for your guidance on me repairing electronics throughout the year 2009. Only by your guidance I could reach my achievements today and still have the power to be in this repair line, though now it’s still in the halfway to becoming a real pro. Let this year be an amazing year for both of us.

Thanks and it is also your hard work that pay off!

A fellow of church brought in a brother fax-275, and the problem is only the figure 9 on the keypad is not functioning. After opening I saw that someone had modified the circuit line path of the figure 9 button, see the black modified path. I am very curious to know what tools did he use to draw this kind of path. Now, his modified black path has broken somewhere and I got to reconnect it.

How do you repair this kind of a problem? I can recall the conductive pen in your blog sometime ago. Can I use this to reconnect it? Have you ever used this kind of pen, is it also black-colored?

Yes you can use this pen and it is silver color. I had used the liquid type and it works too!

It’s a pity that this pen is not available here, could you suggest any other method to repair?

Usually this is the best way to make a circuit. Sorry, i do not know of any way of connecting it. If you buy this pen and use only once then it is not justify the repair cost. May be you can try to ask mobile phone repairer to see if they can connect it for you.

Jestine

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

ok sir..,can u give me some suggestions to rewind the coil,pls..

Can v replace IRF630MF with IRF630 ?

Hi Jim,

Yes you can use the B+ FET as replacement. To rewind the coil, just remove the bad wire and replace with the same diameter of wire and with the same length.

Jestine

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Hi Teck,

Happy New Year to u & your family. How are u?

Fine thank you.

I got a chance to remove the back cover for my 34” CRT, used a stick to hit the pcb located at the neck of the CRT but was unable to confirm whether the fault is from there. Sometimes the yellow will go off & return again without touching anything on the TV set.

Most probably in that area. Try resolder the RGB transistors.

I plan to remove the pcb & re-connect. Is there any high voltage locate at this pcb (the one at the neck of the CRT tube)?

No, but becareful not to touch on the anode cap at the picture tube.

Is wearing rubber glove & rubber shoe safe enough to work on a TV?

Not really. You need an isolation transformer.

Have a good day!

Jestine

http://www.JestineYong.com

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hi jestine

i was just wondering if we don’t have esr meter, if we can detect bad caps with freeze spray. Will freeze spray help to temporarily lower the esr (cold decreases resistance) so that the bad cap can be spotted when the spray makes the equipment work again?

regards

Ravendra

HI Ravendra,

I have tested many caps by using the freeze spray and the ESR value were still the same. Thanks for the video links.

Jestine

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HI B,

By the time you read this email, I will have purchased your SMPS e-book.

Thanks!

I hope that you will support me more than last year, because in this year I am going to spend more of my time repairing electronics.

No problem!

By the way, the old Sony 14″ CRT monitor’s problem remains, after I replaced the vertical IC ( uPC1378H ). I had also changed some capacitors related to this IC. Moreover I had replaced the H&V Synchronization IC ( TDA2579 ) after knowing replacing the vertical IC didn’t work out, but still the problem remains.

Sometimes the problem could be due to convergence board too located at the top of the neck of picture tube. Try gently hit it to see if there is any changes or not.

In my opinion to be a real master in the monitor field, one has to be able to know exactly what component related to what IC at pin no.X has problem. In other words, one should be able to know what is the function of every pin of an IC. Only in this way, he could be more successful in repairing any item. I really hope that you will guide me to point out to component related to certain pin of an IC has problem, f.e: sandcastle output pin, flyback pulse input pin, etc. What do you think?

Yes, you are right. The best way to test this is to get a good working Monitor/TV and pull out one by one the IC pin and see the symptom for your self. Record it down for future use and make sure also that you have the spare IC. Just incase if you spoil the IC, you can replace it.

jestine

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Dear Jestine,

It is ok to test onboard of the flyback transformer secondary, the transformer in the horizontal circuit, the transformer of the SMPS power supply using the blue ring tester.

Berlin

HI Berlin,

Yes you can test on board. Before that you must do some testing first on these components in order to familiarize with the reading. Assuming you have doubt testing on board then you can solder it out and test it off board.

Jestine

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

HI B,

Which do you think is better a capacitor with lower capacitance value or one with a higher capacitance value if both have normal ESR value?

For example I need a electrolyte cap 100u 35V and in my compartment there are one which is 90u and the other is 110u.
In your experience a bad electrolyte cap found in a board with higher ESR value, how about its capacitance value, higher or lower than the nominal?

I will prefer the higher capacitance. The high ESR cap, usually have a good capacitance value. Due to this, it is always adviceable to use ESR meter to test e-caps.

If a monitor come in with its delfection yoke has been wet with rain water, how should I dry it?

Use hairdryer on mode 1 (lower heat)

Are you selective to receive the monitor unit from customer? For example how if one of your customers bring to you an old monitor with 8 or 9 pin TTL connector?

Normally i would tell them that we no longer repair such old Monitor. I will tell them that we do not have the system to test it and most probably do not have parts too.

If I look carefully the latest VRT data book in the transistor part, some items are just being skipped in the list, f.e.: they list transistors 2SC5504, and then 2SC5506; the 2SC5505 is not there. In your opinion why this item is skipped? For your info, this skipped item can be searched by alldatasheet.com.

It could be the person who did the compiling work could not get that data at that moment. Perhaps the next edition you will surely see the number there.

Have you ever seen 2SDXXXX being used as a HOT transistor, instead of a 2SCXXXX, because in the article of transistor marking codes, it is said that 2SD is a NPN AF transistor?

Yes, but that was very old Monitor. More than 15 years!

Jestine

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Sir, I have received the digital capacitance meter and blue esr meter last jan 5, 2010 in good condition. I have some question about soldering iron, I find it difficult to desolder the electrolytic capacitor from computer motherboard for replacement because of bulge cap, is there any soldering iron especializes for computer motherboard? I have 40watt soldering iron, don’t remember the brand, but the store said it’s made in japan.

God bless!

Hi Marlon,

First, apply solder to the capacitor 2 pins then use your right hand (holding solder gun) and melt the solder, then use your left hand to pull out the cap while the solder tip still touching the cap pins. Get the hakko 981 solder gun to do the job.

Jestine

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

Can you give me a step by step to check a dead crt monitor?

How to eliminate the problem at primary supply,secondary supply,horisontal regulator, or HOT?

May be for example desolder the main transformer to check the primary, if its okay the resolder the transformer and desolder the HOT or horisontal regulator.May be something like that sir?

I mean how to check each section? like the primary,if primary ok then continue to secondary, if okay then etc..

Because when repairing a dead monitor I don’t have any clue where to start to check,what should I do then.

What is B+?is it correct that B+ is main filter capacitor + voltage?

I’m beginner sir, please help.

Thanks.

HI Julianto,

Can you give me a step by step to check a dead crt monitor?

How to eliminate the problem at primary supply,secondary supply,horisontal regulator, or HOT?

May be for example desolder the main transformer to check the primary, if its okay the resolder the transformer and desolder the HOT or horisontal regulator.May be something like that sir?

I mean how to check each section? like the primary,if primary ok then continue to secondary, if okay then etc..Because when repairing a dead monitor I don’t have any clue where to start to check,what should I do then.

Sorry i do not have any ready articles on this. I suggest that you visit this website:

http://www.repairfaq.org/sam/monfaq.htm

or even get a Computer Monitor troubleshooting book from amazon.com that could help you out. Check this link too:

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

To isolate tv faults.

What is B+?is it correct that B+ is main filter capacitor + voltage?

B+ is the voltage that supply to flyback transformer.

Jestine

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Hi B,

This monitor retrace line problem is there without any input signal, just by turning on the monitor. Do you think I still need to replace the preamp IC, as seen in the attached photo Sony 7D004. I couldn’t find this IC data on the net.

Well, sometimes if we never though of a circuit that can cause the problem, it may turn out to be that circuit have problem. Sorry, i can’t find the IC data too.

By the way, to repair this monitor I have bought some books to get a reference. One book is about repairing the TV, as attached. Now, what makes me confused is this retrace line problem is caused by vertical circuit ( as you said ) or by the horizontal circuit. I think we as a repairman couldn’t be ambiguous about rectifying this problem, right. Or is it TV retrace line problem is different with monitor retrace line problem?

The picture that i saw was horizontal sync out which clearly indicate the fault in horizontal circuit. Tv and monitor retrace line problem is the same. Usually check on the G1 or the Vertical IC circuit.

Another interesting question is, could we just put the picture tube without attaching the high voltage flyback anode?

May i know what purpose? Some Monitor design, if the anode did not connect to the picture tube the HOT will immediately blow upon power On.

For example, in this monitor after doing this, when I reattach the flyback anode and turn the monitor on, there is high voltage noise sound heard from the picture tube. Could this sound be caused by the damp air got into the picture tube, because now here we get rainy season？And this sound is still there until now.

You mean that you have connected everything back to original and the sound is still there? If yes, then check the high voltage KV, because a higher than normal KV could cause such sound.

Jestine

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Hi jestine ,

i have a nordmende crt tv , the tv set on standbay only never turn on , no power ic provided to be checked i used to replace the power ic then the problem is gone , bridge retfier pins are receiving the 235vac,but there is no 150 dc output from the bridge rectfier ,i removed the 4 diodes and checked them and it were good .what else please should i check .

Best Regards
Bassem

Hi Bassem,

I guess you need to directly replace the bridge and retest. If there is any leaky component along the bridge output then it may pull down the voltage.

jestine

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Hi Jestine

Let say a power supply board for an example there is 3 x dc cap 470uf 50V connected in parallel and as we know the total is 1410uf(3x470uf ) ,voltage rating remains the same and when we checked by the blue esr meter which line on graph should we refer to?

And if one of the cap fails in uF or its esr value ,in this case would the blue esr meter able to detect which cap is defective?

Thanks!

Regard

Yong

HI Yong,

ESR meter can’t detect cap connected in parallel. If you see the caps connected in parallel, you have to desolder one pin in order to test it. Try check my article here again about parallel cap:

http://www.electronicrepairguide.com/esrmeter.html

Jestine

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Have a nice day Jestine, I have one question to ask you regarding this IC SE140N

normally voltage at pin 2 is about 19V and output pin 2 normally 142V what if the voltage at pin 1 suddenly increase to about 150-170V and the B+ Voltage shut down and drop to 0 volltage, is it the opto coupler at fault or the ic itself faulty.SE140N is the error amp IC.The B+ Voltage normally 110V increase to nearly 180-200V.

Thanks

Andi Sapli

HI Andi,

If other output voltages from the SMPS are good then it can be both or either one of them have problem. Try direct replace and retest to see the result. By the way, i have a good news for you. you can now proceed to this download page and download again the SMPS in pdf and print it out for easy reference.

Jestine

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Dear Sir ,

I just brought the ESR Meter, can you teach me how am i going to test it on a capacitor , example 47uF 200V what will the reading show . Thank you

HI Lily,

Turn on the meter, short the probes and press the on/off button again to reset the LED to “00”. Base on the chart that i have given you in the meter box. A 47 uf 200 v have a reading of about 1.5 ESR ohm. If you measure the cap and you get lower than 1.5 ESR ohm then the cap is good. If you get about 1.5 to1.7 then the cap is marginal. If you get higher then 1.5 like 3.9 or even 20 ohms then the cap have problem. Use the meter to perform more test and you will know if a cap is good or bad. Just in case if you did not get the ESR METER chart then please click the link below:

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

Jestine

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hi jestine

i have two hp atx power supply the problem is that when u insert power cord it start by itself without shorting green & black wire (it doesn’t work in the board)

thanks

HI Hilary,

It could be the transistor inside the power supply that controls the on/off had shorted. Guess you need to open the casing and check the transistor.

Jestine

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

please can you assist me in getting Transistor for my projector PARTS NO AVS12CB or its equivalent.

I’ve try so hard to get in our local market and in south Africa but to no avail if you can do it for me I will be so much grateful.

with lot of thanks,

Hi Eugene,

Try this link:

http://parts.digikey.com/1/parts/991187-ic-switch-automatic-volt-to220ab-avs12cb.html

Jestine
http://www.JestineYong.com

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

Dear Mr.Jestine,

How to check no display but the power led is on in the crt monitor? tq

Hi Julianto,

Is there high voltage or not? If no then check the B+ voltage to the flyback and make sure the HOT have base signal.

If yes, then check the heater voltage and G2 voltage. Make sure G1 voltage have negative voltage of about -20 to -70 vdc.

Jestine

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

hi mr yong.

As you know, one of defective mode of electrolytic capacitors is that,capacitance of them be decreased.

are ceramic capacitors like this? (i mean that capacitance of them to be decreased as well)

thanks a lot.

Hi Saeed,

The ceramic problem is either capacitance decrease or shorted.

Jestine

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

I have a question for you. I hear many people talking about soldering flux. I know it has to do with soldering but what exactly does it do when it comes to soldering..thanks

HI Waleed,

The function of flux in soldering is to clean the surfaces to be soldered. It is usually included as a core inside the solder wire and flows onto the surfaces to be soldered as the solder is melted. A side benefit is they improve the appearance of the soldered joint.

Jestine

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4 Comments

Sarvasri

January 22, 2010 at 7:38 pm

I have an Optiquest 24" monitor that when it comes on shows only two groups of fine vertical lines (3 inch wide bands). I don't have fancy diagnostic equipment. Just a nice multi-meter. Can I fix this monitor? It has two boards, a connectivity board and a power board. There is also a small board connected directly on the back of the display covered by a metal shield.

I don't know how to find which board is bad or what part is bad on the boards. How can I fix this monitor?
I can send you a small photo of the problem, but I don't know how in this comment box.

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admin

January 23, 2010 at 8:21 pm

Hi Sarvasri,

The problem is in the LCD PANEL and is beyond repair because there is no part.

Jestine

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Gremloyd

January 23, 2010 at 10:29 pm

Hi Sir i hve a problem regarding to ethernet controller driver rtl8139d i search a lot and more site to the net, i did not find anything!cn you give me a site where i download that driver compatible w/ windows vista tnx...more powe.....

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admin

January 24, 2010 at 9:22 am

Hi Gremloyd,

Sorry, no information on that.

Jestine

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