Are there any burn marks on other components and PCB tracks?

Yes sure I will help.


Jitender

Wats the icnumber??? Vcall me at 8093864974

First step is to identify the part.
It is not an IC.
The component in pic  is a N channel MOSFET transistor in SO-8 packing.

pins 5,6,7,8= D        Left hand side ,Connected to +ve
pin 4= G                 upper right hand
pins 1,2,3= S          lower right hand

If it has a crack then for sure damaged.
Most probably a part of the DC-DC converter stage of the charger.

Jitender

Sorry for Late Response

Swapnil : There is a crack in that chip.
Jitender : Thanks
Shauviks : IC No. is 6680 (Delta Symbol) 1L3H
Jitender : What should I do now ?? Can I get this Mosfet in local electronics shop ?? any substitute of it ?

Any one like to give his suggestion or solution ??

Shauviks : Definetly I'll call you tomorrow

the solution is simple. 1st try to find this mosfet, if available change it, if not then look for substitute . I have not had time to look at the specifications of this device , hence can not comment on a substitute. But I am sure a sub will be available as where it is placed in the circuit matching the specs should not be critical.

jitender

Firstly, dont Panic, It must be repairable if it is not the microcontroller or the display.
Trace the Power circuit first. It may be a back preventive diode like thing that may blow the fuse (Zero resistances) or may become short.

Check
http://html.alldatasheet.com/html-pdf/51505/FAIRCHILD/FDS6680/406/1/FDS6680.html
Try IRFz44 (More Powerfull) though RDS is higher, but no problem if starts.

First make sure about the microcontriller circuit and check the digital positive rail and negative rail.
Then the sensing resistances (for cell voltage and currents) if any

And checking the uC voltage range of operation, have to check the controller ckt is OK or not (with separate 5V supply).

And, of course, first open up the large electrolytic capacitoirs and test if become Short.
Then the power high speed diodes in the Power incoming circuit so that track wont burn ups.

Please keep in mind that nothing is impossible. But have to check economical or not !

Good Luck.

Hello Kalyan Ji,

I dont have any electronics background, so I only undertand is I can test it by changing FDS6680

Rest is alien language for me.......can you help me buy telling me in brief (with images if possible)

Thanks

Electronics needs patience, nothing else. (book reading also have the same key )
If you get the same,FDS6680, you can replace, but have to check before replace that it will not blow again for short circuit in another place.

In most circuit, large electrolytic capacitors (cylinders) connected with positive and negative supply to smooth voltage fluctuation and they are sensitive in voltage reversal (We call it polar device i. e. we have to connect in correct polarity to get best, and can ruin in reverse polarity.). So, they are to be checked before replacing the MOS. And, they have to open up (or de-solder from PCB) to check their health. Most time, they shorts internally and blows the diodes (here inside MOS) . So, you need to check and if require, replace the capacitors too.

And, look at the PIN Configuration of IRFz44 (3Pin MOS) and FDS6800. The only difference is that FDS6800 have source and drain with multiple pins. In case of scarcity of FDS6800, you can short those pins(ources together, drain together and gates together, not all together) and may connect similar MOS. the differance in resistance will generate more heat, but it have a larger capacity and above all good heatsink.

Thanks

Quote from: jitender on April 03, 2012, 08:33:38 AM
First step is to identify the part.
It is not an IC.
The component in pic  is a N channel MOSFET transistor in SO-8 packing.

pins 5,6,7,8= D        Left hand side ,Connected to +ve
pin 4= G                 upper right hand
pins 1,2,3= S          lower right hand

If it has a crack then for sure damaged.
Most probably a part of the DC-DC converter stage of the charger.

Jitender

Damaged Component identification most imp part---in this case DONE
Second find the part --- in this case DONE 
http://in.rsdelivers.com/product/fairchild-semiconductor/fds6680a/trans-mosfet-n-ch-30v-125a-8-pin-soic/6710605.aspx

Now just order and replace it.But make sore u orient the dot at the corner of the package.

Send a pic of the reverse side, lets have look at it to see what is there.

Jitender

Quote from: jitender on April 03, 2012, 08:33:38 AM

Send a pic of the reverse side, lets have look at it to see what is there.

Hi,

There is nothing on back side, I mean pins are only solder on top and not going in back side.

I also have done some testing may be it is usefull to identify,

I gave 15v power in curcuit, and test on multimeter,
Red Spot : Where I connect +ve wire of Multimeter
Black Spot: Where I connect -ve wire of Multimeter

and mention how much voltage I am getting on those pins

pins 5,6,7,8= D        15v
pin 4= G                 15v
pins 1,2,3= S          2.8v on Each

Jitender Sir,

Uploading pics of back side as you asked in PM

Also pic of crack MOSFET, and Yes DOT is also clearly visible on Mosfet for polarity

and Finally I find another same MOSFET on board, near to Output side

Source to drain voltage shows high voltage drop for high impedance of MOS.
But try to trace voltage regulator like TL431 and with it's feedback resistance, you will get  the required voltage at MOS Drain/source fed to the internal rail.

And please open the capacitors and check.
whats about the current during this testing ?

Kalyan Ji,

I am hardly able to understand, what are you saying because as I said i am not form Electronics Background,

I only repair my electronics on component based, not by deep electrnics,

Even I dont have resistance meter ......

can you tell me all these steps in easy language ??

GBISHT,
as you replace component basis, after searching fault, you have pation to electronics and more dedicated than 50% of electronics engineers I have seen. Please buy Albert Paul Malvino's "Electronics Principles" specially 3rd Edition if available and keep as reference (cost hardly 300Rs). Your scattered electronics knowledge will get the base and will make TajMahal, believe me. And dont regular study (at least i cannot) just start any transistor biasing chapter and along with designs, you will addicted to it.

Generally, the damaged MOS was working as switching device and not as linear voltage regulator but as switching voltage regulator.
This switch on-off ratio depend the output voltage without power loss (as switch have no power loss). This is called as switching regulator. Now there is a feedback which controls this ratio depending upon the output voltage. If the output goes high (sensed by Tl431 or similar) it stops the transistor gate trigger so that it wont become on and output become low, and when goes just below the level, it again makes off.
TL431 or similar IC goes on beyond a particular voltage. But higher voltage can be achieved connecting the IC to the fraction of desired output voltage equivalent to IC's voltage. This is done by Resistor devider circuit.
So, if you get the voltage divider resistance voltage and the IC sensor IC model/voltage you will know the DC rail voltage that was supplied by the burnt MOS.
So, give the rail direct DC voltage at that voltage or little bit low and check if the digital circuit (Display etc.) OK or not) Else total labout will go wastage.
If no, then search for more fault. Look only electrolytic capacitors damage rate is the maximum and you have to check them first.
Or if the DC voltage seems the entire circuit is OK, then just replace the MOS and make total working as you have check the rest.

Hope I can explain as simple as I can.
Better take help from any electronics friend who is interested in HOBBY Electronics too. Because circuit analysis and circuit separation is the main thing here.
Thanks

(...........and mention how much voltage I am getting on those pins

pins 5,6,7,8= D        15v
pin 4= G                 15v
pins 1,2,3= S          2.8v on Each
[/quote].................)

When MOSFETS fail they often go short-circuit drain-to-gate.
So you will get same v reading on D and G.

Thanks Kalyan Sir,

As of Now I am really very busy of reading some other books which are more important for me now, but surely I marked that book and read it after finish my existing reading material.

OK So what I understand Is this MOSFET give power to circuit in controlable fasion, and save circuit for high and low voltage......

As you said, (May be I understand wrong), I have to shot the circuit and have to buypass the MOSFET.....

So I did same I connect Pin4 (G) with Pin1,2,2(S) together but it didnt work,
Today I also bough capacitor which is near to MOSFET so I changed it with same value and then tryed same thing.....

and waallaaaaaa ,  This charger is geting alive again.......wow

So I think after replacing this MOSFET (which I have already ordered) that charger will work again 

Attaching Pic for refrence, also made video but it is 180 deg oppt..

Can I use it without this MOSFET I know silly Question ........

I dont advise you to use the charger yet. Better wait for the mosfet to arrive. Do not hurry.

Jitender Sir

Now I m not using it and wating for component.
It will take 7-8 working days

Oh, Nice to see it's working.
So, you are not any way behind than a normal electronics engineer.

Look, Capacitors are most problem giving device. Same thing happens to Computer Motherboards too. And sometimes, running with faulty capacitor damagr FETs also.

And I recomend you to replace the Capacitor with higher voltage level capacitor to be in safe side if space available. You have replaced with 85^OC Capacitor. But use 105^OC Capacitor. (though your capacitor have higher ESR, but life is higher, but it may arise problem later.
You can also make parallel an .1uF disc capacitor parallel to it to lower ESR.

Thanks

Thanks, But I am Computer Engineer......and very far from Electronics Engineer.....hahahaha

But this hobby is pushing me to do these things.......

no Problem, now I have spare capacitor of same value, so ready for it..

also wating for MOSFET, probably it will take atleast 10 Days to reach me.

So lets wait together and see how much sucess we will get in this...

Hi Everyone,

Again an Achivement   , today I received replacement of faulty MOSFET  and without wasting time I went to Mobile shope and replaced faulty one.

And now it is working, not charged battery yet, but I hope it will wrok fine

Pics after replacement of MOSFET.

I like to Thanks Jitender Ji and Kalyan Ji for their Expert Advices, +1 for both

Thanks a Lot

Oh, really feel HAPPY.
It's the winning of our forum RCINDIA - RCing with open mind.
LONG LIVE RCINDIA.