Electronics Repair Questions/Answers and Testimonials- Part 38

I've been reading most of your posted troubleshooting techniques. It is very informative and very helpful specially for those who are new in new technologies. I was able to purchased one of your recommendation of having CapAnalyzer 88A which is very essential to my troubleshooting job. 

May I request if you may, to discuss some troubleshooting of digital pianos. I have Roland E-14 model (1997) which has an initialization problem. I think it has something to do with microprocessor. Unfortunately, the service manual of this model was not complete in terms of troubleshooting in the CPU module. The unit was designed to reset upon turning on.

Thank you for your time reading this request.

 

Hi Lemuel,

Thanks for the email. Since I'm not into music equipment repair thus i do not have a straight answer to this. For checking if the microprocessor is good or bad is 

1) make sure the supply voltage to the ic is good
2) make sure the crystal have a good sinewave.
3)  by comparison if it can be extracted out
4) by replacement and make sure the IC have the same program.

If 1 and 2 checked to be good and you do not have any extra ic for testing then the best way is to replace the mainboard. In the meantime I suggest that you try to find if there is any piano repair forum.

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Jestine

 

Hi Jestine,

pls i didnt understand what you mean i my question 6 which you told me to isolate the problem by removing the mainbord.if i remove the mainboard as a matter of power blinking,how will the monitor power without the mainboard?

 

secondly,how many voltages are found in lcd televisions?

HI Victor,

If a good motherboard is connected to a power supply board, the power supply will continue to produce good and stable voltages. If the motherboard have problem (something shorted) it will cause the power supply to shutdown or fluctuates. This is the reason why I want you to remove the motherboard to see if the power supply is good or not. If the power supply suddenly turn good after the removal of motherboard then we can conclude that the motherboard have something shorted/leaky which you have to check. It could a chip that already turned hot and etc.

Secondary side of LCD TV can be 24 VOLT, 12V, 5VOLT. Some use 18volt for their audio board.

Jestine

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Dear Sir 

I have a Question Sir please define me the easiest way to test CRT TV fly back transformer?

 

Hi Abdul,

By using a high voltage probe you can check if it has good low or no output voltage. if you would like to check on the winding you can use Blue Ring Tester.

Jestine
http://www.JestineYong.com

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Glad To Meet You Again !!!!

With Your Help I Successfully Repaired Many Monitor. Now I Am Facing A
New Problem. In My Customer Monitor I Found The Burnt Resistor Using
My Repair Friend Help I Found The Value.

Now Problem Is IC. It Was Shorted It Was TEA 1530AP . Monitor Did Not
Turned On …

In My Market That Particular IC Not Available Can You Tell Me The
Correct Substitution Of TEA 1530AP can i put another IC ?
Kindly Please Guide Me …. Your Only My Hope Kindly Update Me As Soon
As Possible …I Am Waiting For Your Kind Reply ….Please Tell Me
Correct Substitution I Searched On Internet Cant Found That Please
Kindly Help Me I Am Waiting For Your Reply
— 
Thanks & Regards
B.Ragavendhran

Hi Raga,

Try this website :

http://www.utsource.net/TEA1530.html

Sorry no info about the replacement the best is still use back the original part.

Jestine

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Hello;

I forgot to ask,what  components can be tested in circuit and what can be tested out of circuit,this includes any capacitor.

Thank you.

Hi Paul,

In circuit are fuse, coil, electrolytic capacitors, thermister

Out of circuit are transistor,diode, zener diode, varistor, resistor, non polar cap and etc.

Jestine

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how to identify the Bad IC and test it

Hi Bryan,

You can:

use your hand to touch it-if it is very hot then it has problem

you can use scope to check for output waveform. Have input waveform but no output waveform means the ic is bad

you can check for supply voltage to the ic. Every ic should have a good supply voltage.

Jestine
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Hi Mr. Yong

I dearly thank you for the down link now I again have all your books and am enjoying reading them, I am learning so much, I have had a hobby in electronics for 32 years and now I can say I can finely repair more things than ever before in my life.

thanks again for the download link

John

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Hello Jestine,

sorry to trouble i need some confirmation on some diodes i am checking,on a smps,

SR510 711

FR157G 0728

0732  MBRF20100CT

0728 MBRF1545CT

i believe these to be schottky diodes as per symbols on diodes an internet search,

i am checking them with an analouge meter as per your ebook,i am getting a forward bias reading,

but i am not getting a reverse bias reading(nothing)on all diodes 6 in total,

i am a little confused as i noticed on reading John Prehers tv ebook,he says not all scothkky diodes give a reading both ways,if thats the case how do i confirm they are good or bad,

the analouge meter i am using is a UZ82D from Maplins elecronic store,

 

kind regards

 Paul

Hi Paul,

John is right as not all Schottky diode will have two readings. If you get one reading then the diode is good but it has to be tested using X10 K ohm range. The UZ82D analog meter range is only x10 which is not good enough to know if the diode is good or bad. I suggest that you get one Sunwa 360tre model that hav ethe x 10 K ohm range. You can use it to test on zener diodes bipolar transistors and FETs too.

Jestine

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

Hello Jestine, 

Hope all is well. 

I want to share a experience I had with a LG 19 inch LCD monitor.

The monitor would turn on normally but after 10 minutes half the screen would turn dark.

I suspected the LCD controller board and used some freeze spray to troubleshoot. Sure enough after spraying a IC chip on the controller board the screen went back to normal. After a few minutes half the screen once again became dark. I sprayed the IC once again and the screen went back to normal but this time stayed that way and did not return to a half dark screen. I left it on for 6 hours and the problem did not return. To play it safe I resoldered all the connections on the IC. After 24 hours it still is working correctly.

Have you ever had a IC chip that repair itself after being frozen several times?

Vic

Hi Vic,

Yes I came across such problem but it can't repair itself. After resolder the equipment worked perfectly good.

Jestine

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

Your Name: Nirmal 
Message: I just came across this site while searching smps. I was curious to know whether I can replace 1kv R ceramic disc capacitor with 2 Kv cap in my smps? Will this cause any issues?

Hi Nirmal,

Yes sure you can replace it with 2 kv.but make sure the cap value is the same.

Jestine

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

Hi jestine, how was day.
Sir i have a sharp crt television 14inch that have the problem of horizontal line, i have replace the vartical i/c with good one and the valtage supply to the i/c was 24v i also replace all the capasitors at the vartical side and yoke coil but still there is horizontal line. Please i need your helf. Thanks.

What about the jungle ic that supply vertical signal to the vertical output ic? In this situation you may need to use a scope to find where is the missing signal. It can be caused by bad resistor.

Jestine

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Hi Tyrone,

I have not use any replacement for the above diode but you can try use UF5408 as replacement to test it out. Please do not use 1N5408.

Jestine
http://www.JestineYong.com

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

Hi Yong
I know for sure that I am not qualified in the field of electronic
components test and repair and I would ever find the solution to all
the problems but as I receive your ebook , I read it for several
times, feeling very impressive and knowing that your book is very
significant to me.

Before, I know nothing about repairing electronic component but now I
gain so much from your EBOOK

Thank You Mr Yong

I hope I would do better in this field (Electronic repair)

Yours sincerely

ARETI E
REPUBLIC OF KIRIBATI

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

I would like to ask if it is safe to troubleshoot [making voltage reading] on powered on monitor while the anode cap is not connected from the CRT and away from the circuitry? I have to remove the circuit board from the casing to have a better view of components for measuring voltages.

The unit I am working on has a problem with retrace lines while the screen is too bright.

Thank you for your guidance.

Hi Lemuel,

In some Monitor you ca do that but to some it will burn out the Horizontal output transistor (HOT) because you are not connecting to a load.

Jestine

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

Dear Mr. Jestine,

 We have a speed controller ( FSP200-3), the following parts are damaged in the controller , for fixing the controllers we need their datasheet or equivalent code, would you please help me and tell me their Datasheet or equivalent code.

1-SMD transistor with  B3 code

2-SMD transistor with KDE code

3-SMD diode with 1H code

4-SMD Zener Diode with 101 code 

BR

Jokar

Hi Jokar,

Sorry I don't keep any datasheet info. You can try 
http://www.marsport.org.uk/smd/mainframe.htm

Jestine

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

Hi Naor,
 

In your book you mentioned some component that need to take of from circuite,what about other components?

Can it be checked onboard?

You can check fuse, thermistor, small coil, electrolytic capacitors on board. Other components that need to check off board are:

diode, zener diode, bridge, transistor, non polar cap and varistor

How do i Identify some components on the board? Some do not have a visible letters on the part or could not find them in your book,im sure they exicte but not the same in photos.It will be helpfull if there was some photos with all kind of types components??

By looking at the board marking or read the part number and refer to datasheet website.

 Jestine

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