Dear Jestine

Can I use IR thermometer gun to locate the short circuit (high temperature) of  component on a “turn on” pcb board especially the ICs instead of  touching them ?

Would the shooting of  IR light damage or affect the operation of  component or ICs?

Pls kindly advice

Thanks

HI Yong,

I have not try using the gun before but it will definitely not affect the components.

Jestine

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Hi Daud,

SIR, what is difference between current  sense resistor and startup resistor in switch mode power supply? and also define identification of both resistors. A brief material on above will be highly solicited.

Current sense resistor is to sense the current drawn from the secondary side while start up is to lower the main supply voltage to a lower value (typically 12 to 20 volt) for power ic to use.

Start up could use carbon film and metal film flame proof but for current sense usually is metal film flame proof.

Jestine

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Hi Ehab,

I work with some communication devices like the Motorola cp200 hand held uunits and other types .

Now to test or repair these units you need to reach the i.c. inside .

How to do so when the i.c. is protected by

1. An aluminium shield for E.M.F. to stop interference .

You need to temporarily remove it  but you must ground yourself with wrist strap

2. Below the shield the i.c. is covered with a matter that looks like soldering flux and in order to reach the i.c. you need to remove this matter .

I guess those are silicone and you can Google for “Silicone removal”  to remove those silicone before testing.

Jestine

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Hi Jestine,

Can you identify for me this type of Zener?

Thanks in advance,

Bruno

HI Bruno,

Do you have other working zener diode just like the photo? If yes then you can compare the reading with a good one. But you may need to test on few zener diodes in order to find out the value. This is the nearest code that i can get:

http://www.marsport.org.uk/smd/sod80.htm

Jestine

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Hi Ng,

I used to have one Sony TV that happened exactly the same as my Panasonic TV that had problem now. The Sony one I had not used for almost 10 years, it only 3 years old when it lost the audio on itself, but if I connected to VCR, it had the audio, the technician told me a lot of the same model TV he encountered were having the same problem. He also told me if I wish to have the problem fix, I have to change the board. Therefore, I put it aside in my store room for almost 10 years.

Now I had the Panasonic TV which have the same problem like the Sony TV, but this Panasonic TV even I connected to DVD player it still have no audio. I did not tried the VCR, howver, I will try it when I dig it up from my store room.

So is this the IC problem?

It could be dry joints, bad audio ic or even missing supply voltage to the audio ic. You need to open it up and check.

Jestine

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Hey Jestine

i have a Dell E173FPF 17″ LCD monitor

my problem with it is that after a while being powered on the screen starts to “Tremble and roll upwards”

i have redone the cold joints that i have found however this has not help the situation, any help would be greatly appreciated .

Dominic

Hi Dominic,

Make sure the output voltages are good and stable first. If it is good then susepct a bad mainboard. Using a coolant/freezer is the best way to detect the fault because you have mentioned that the problem only occur after a while.

Jestine

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Hi Jerry,

Please guide me how to use the blue esr meter.
Turn on  the meter, short the probe and press the on button again to make the display to become “00” . Now you can test e-caps on board by referring the value on the chart that I’ve given above. The value that you get should be lowered than the chart value. From the chart a 22uf 250 volt cap have 3 esr ohm.  That means the value that you get when measuring 22uf 250 volt should be lowered than 3 other wise you need to replace it. If you have a marginal cap say 2.8 or 3.1 ohm, as for me i will still replace it because if you did not replace the particular cap will give problem probably in 3 ,6 or 9 months time. It can even give intermittent problem.

Jestine

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Hi Jestine;

I finally ordered your book, LCD monitor repair.

I have to do some studding, but I do like your approach to trouble shooting , and will be reading that section several times.

I have a DCL/LCD 9A, 19″ LCD Display.

The problem is after hitting the power switch, the blue led comes on and the screen displays the windows logo and icons for about 2 seconds then the screen goes black, led power light stays on.

I have tried recycling the power switch on/off for up to maybe 10-12 minutes and then the screen stays on and works great. Where should I be looking, voltage wise for this problem?.

Any help would be appreciated.

I do not have a schematic for this unit, and can not find one on the net.

Regards

Peter

HI Peter,

First make sure the output voltages from the power supply are good and stabil. Next, make sure no dry joints in the high voltage transformer pin. Make sure also no bulged -cap . if there is any just directly replace and retest. Check also the capacitance value of the ballast capacitors and tuning capacitors. If all check to be good then one of the backlight may have problem. A weak baclight could cause display shut down problem.

Jestine

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i have a problem with a circuit board that has two 25v /56uf caps that i cannot get for a gateway GTW-17M103 tele,are there sub that i can use ,or can caps be parrallel or ,series,and what types if any

HI Byron,

Try this link:

http://electronicrepairguide.com/series-and-parallel-capacitors.html

Jestine

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Hello sir,
sir i have problem in repairing power supply of the above television, i found power transistor S2000AF is shorted which course fuse to blow, i replace the power transistor with the same part number and it get shorted again then i replace it with power transistor BU508A and even this one is get shorted, and the power is using the power i/c TDA4601. Sir what you think is the problem that course power transistor to get shorted, can i suspect the power i/c or power transformer primary winding? Thanks you sir, i hope you guide me to the right way inorder to tackle this problem. Have a good rest sir.

Hi Mukthar,

Try this link

http://www.jestineyong.com/?p=403

Jestine

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Hello Jestin sir,

I need data of sk m583 device. the component image is attached. is that device is triac or mosfet?, I founded taht component is shorted in hp laserjet M1319fmfp printer. Please inform replacement component, please help me sir.

Hi Bala,

If the component is located in the heating element circuit then it is a Triac. Sorry i could not find any details on this components.

Jestine

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sir,i have read your book ‘testing electronic components’ deeply.it is an amusing book, thanks.sir i have a videocon tv with sound normal but as per picture is concerned there is only a horizontal line at the upper corner of the screen, what could be the possible fault and what components i have to check out? Please help me

HI Sahil,

Make sure the supply voltage is good and no dry joints in the vertical ic area. If all check to be good then direct replace the vertical ic and retest.

Jestine

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Dear Sir ,

I got one unit of HP LCD Monitor ( 2065 ) send in to my shop for repair , the complaint was no power after i check the board i found out only fuse and the rectifier that faulty . So i replace the faulty component and the LCD back to life but after a few hours the LCD don’t have power again and i recheck the board again still the rectifier and the fuse faulty . What would be the cause of this problem , did i need to replace TOP248YN too or the primary winding got problem . Pls advice , thanks

Hi,

Did you replace with the same fuse and the same type of rectifier? Check also to see if there is any dry joint in the power supply section. I do not suspect the POWER IC TOP248YN and primary winding because if both components have problem the power supply would immediately blow. I will only suspect power transformer if you have check all the components in the power  supply.

Jestine
http://www.JestineYong.com

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Respectable and honorable sir,
Jai Hind (Jai means Victory and Hind means my India)
thanks for your valuable suggestion,whether used one or brand new one,
what about life of the CR tube, digital LED/LCD screen in approximate
hours of use, my CRT TV set has almost gone defective in a life span
of 10 years for use of 3-4 hours a day.
Thanks in anticipation from your fan.
Kulwant

Hi Kulwant,

Thanks for letting me know the meaning. Usually scope usage is very low because we do not use scope everytime in electronics repair. We only use it if there is any tough problem or you would like to check on the signal. I have a crt scope that i bought in 1997 and still functioning today. As for the digital scope, i guess it has the same reliability or even better because it uses low voltage as compare to CRT tube.

Jestine

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I think the problem is on power supply all voltages are low,Justine am
confused you are my lecture can you be patient with me,i want this
field to be my daily bread.what i dont understand a tv using
transistor md1802fx i do have collector voltage and no base voltage
how came l have output voltages?…i have a claint who brought a 74cm
tv with no HOT no schematic what advertise or transistor l can use?

HI Thulani,

The collector voltage is from the B+ power supply. The base needs only 0.6 volt to conduct thus the voltage to the base of HOT is very small. Check from Google about how a transistor switch and you will get a better picture of it. If the set does not have HOT and no schematic then it will be a problem you need to test different part number nad if the HOT RUNS COOL then you can use it. Try transistor with C5047 first.

Jestine

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hi thanks for your help can i ask it is accurate to check these with caps with esr leak seeker also confirms a short

If the capacitor have a heavy short circuit you can trace it using leak seeker. if the board you are troubleshooting have less components then using a normal analog meter set to x1 ohm will do the job.

Jestine

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hello jestine yong,I just want to ask one simple question.from amplifier pcb connector they got marking -15v and the other +15V.Can a measure using multimeter with pos lead to +15v point and the other neg lead to the -15v.Can i got the reading this way or must neg to gnd.needs your helps.thank

Hi Tugino,

Yes your black probe just put on the ground and the red probe use to measure the positive and negative point. Your digital meter will show positive and negative reading.

Jestine

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HI JESTINE

please open the attachment . these components are like resistores but they are not? . over pcb and beside of these things are written BD  and a number i will be thankful of  you if you tell me
what are these thing?.

HI Beh,

Yes i have got the link thanks but at current moment no time to look at it because after the Taiwan trip have lots of email to support. That components is a BEAD (BD) means it is small inductor and you can test it with analog meter set to x 1 ohm and it should show very low ohm.

Jestine

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Hi Boling,
Yes, the monitor doesn’t have high voltage, both G1& G2 are all zero. How should I troubleshoot this kind of problem?
Make sure there is B+ voltage and there is pulse waveform to the base of HOT. Make sure also the internal cap of the flyback is not shorted. Don’t forget to check on the primary winding and horizontal yoke coil for shorted turns.

As for lcd monitor, recently there were lots problem of white screen sent in, but unfortunately I didn’t succeed repairing them. If I am sure that supply voltage to lcd panel is already there, what other factors could cause the lcd panel to display only white screen?

Mainly the problem in the LCD controller board. It is either an open smd fuse to the lcd controller board, bad controller ic, dry joints in the lcd controller board or surrounding components bad in the lcd controller ic.

Jestine