Hi jestine
I am receiving one power supply of computer that customer yourself
says that faulty switch in back of smps alter (150-230) and power
supply burned ,I was opened cover and check and I see clearly two
power transistor burn in smps that their number was tt2148 and I am
replacing their with mje13009 and check again and find two resistor
amount 2.2 ohm and replacing afterward plug in ac cord but smps don’t
turn on and fan don’t spin afterward I was replacing ic tl494 and
lp7510 and plug in again but don’t turn on but voltage in powegood
cord (PGO) is 5.12v,PSO=4.18V,and when pgo cord connected to ground
voltage of 12v wire is 0.8v and 5v wire is 370mv ,pgo=5.12v,whether
you know that where is the problem?can you help me ? I am waiting to
reply!
Have a nice day

HI Hadi,

I suggest that you recheck again the components in the power primary side and make sure you connect the motherboard to a load. Without a proper load the power supply will not work. If this power supply are using a small transformer as a feedback then i suggest that you check the small transistors (mostly C945) at the secondary side. If one of this transistor have problem it will cause the problem as what you have described.

Jestine

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

Hi Jestine, sorry to bother you but this is the DVD player that I am fixing. It is a RCA. Can you tell me what is the component that is marked L 305 in the close up view of the board.

Hi Andre,

L means it is a coil. In the picture L305 is a small coil or bead and can be tested using an ohm meter. It should show very low ohm.

Jestine

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

Hi Jestine I am trying to repair a DVD player that has no power and I came
accross a part that I can’t get and data on. can you help me? the part no.
is D2593

HI Andre,

If it is a transistor then the link is below:

http://pdf1.alldatasheet.com/datasheet-pdf/view/38060/SANKEN/2SD2589.html

Have a good day!

Jestine

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

Dear Mr.Jestine Yong:

I have two defective Model AC4E Nokia Mobile Chargers 5V/890mA for use in 100-240V AC.  The images are attached.  Three SMD emitter bias resistors of Transistor 13001 on the board are burnt in both.   These three resistors are connected as per diagram attached.   Since two resistors in series and one parallel are connected, it is evident that the value is critically arrived at to suit SMD as well as the required wave form.    Any help possible to assume what could it be?   Or any suggestion for trial using a variable resistor (potentiometer)?

Best regards and thanks

Parasuraman S

Hi Para,

Thanks for the photos. It would be tough to find the right value of the smd resistors. Well you can use a variable resistor starting with a 100k ohm and make sure all the components are working fine before you put in the preset and tune.

Jestine

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

Hi David,

I’m reading your smps repair ebook with interest , & thought I would be able to find SMPS problems easily , however think I will need to reads your advise in more detail.

Noted.

I have attached schematic for a smps i’m currently having problems with symptom Stand by volts only , have checked all voltages (test figures no power) comparing defect unit to good unit , Looks like no VCC on defect unit however I have checked VCC line and cannot find any problem ? Any suggestion would be greatly appreciated

Thanks for the diagram. If M10 have problem then the on/off signal will not cause the LED in M7A (optoisolator ic) to conduct.  And if M7A does not conduct M7B will not work. If M7B do not work then the VCCP can’t pass through to produce VCC. If no VCC then the main power supply will not work. However, if there is components problem in the VCCP circuit like shorted transistor Q32 and Q33 or resistors open in this circuit no VCC will be produced. Replace the M10 and retest and if problem still the same then check the VCCP circuit.

Please update me on this repair case.
Have a good day!

Jestine

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

hi jestine
i was checking again the smps i find two transistor with number 2sd667
that have leakage between emitter and collector and replace with
2sd1207 ,the smps works good!
thanks

Hadi

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

I hope from you to help me to find where the problem is.

I have a Samsung LCD

model code: LA32C450E1XZN

S / N: QNLP4BSY324456

The problem in the screen, original image emergence and another image emergence in the little bottom. In the attaché file the picture of problem.

I am really glad to your attention.

Thank you very much.

HI Yassin,

I think this problem could be the mainboard or the T-CON board problem. I recommend  you to check on the T-CON board first. See if there is any burnt IC, loose connection and etc.

Jestine

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

Helo Sir,

I am archana, am going to email you for first time. I don’t have time to introduce my self, so later I will do it.

My problem is am testing ac drives, in that am not getting the zener diode voltage details to purchase, that diode is glass type and in digital multimeter it showing 5.4 M ohms in one side and another side nothing. Please help me to get d voltage of that diode & no details mentioned on it.

Thanking you

Best regards

Archana n

HI Achana,

If there is no code on the zener diode it will be hard to find out the voltage. If the zener diode is good then you can use  a zener diode to determine the voltage:

http://www.electronic-circuits-diagrams.com/testimages/testckt4.shtml

Jestine

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

Hi dear
Plz give me cross refre, mosfet transistor CMT70N03.

Thanx

N dutta

HI Dutta,

It could be from the same family:

http://www.alldatasheet.com/view.jsp?Searchword=70N03

Jestine

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

Hello Jestim
I hope all is well with you and your
I need a hint its, I have a tv crt  that was repaired, and now when I turn on the tv a message appears on the screen flashing “locked” and passed it off and 30 s goes into standby mode.
How can I solve this problem?Ricardo

HI Ricardo,

You may need to look for the service code otherwise  it will be hard to repair such problem. Sorry i do not have the factory service code. You need to visit tv repair forum and ask. Try check also make sure the eeprom ic is getting 5 volt. A lower than normal voltage will also cause symptom.

Jestine

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

Hie Jestine,

It is a crt tv and the problem is that when you switched off the tv
and if you want to switch it on it taken several attempts of switching
on and off the power supply button before it switches on.

Kind regards.

Mwisa

Hi Mwisa,

Try check the filter cap in the primary side. Make sure the supply voltage to the power ic is stable and good. You need an esr meter to check those e-caps. If you do not have one then directly replace and retest it.

Jestine