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Replacing Burned Component of PCB


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#1 williamws

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Posted 15 August 2014 - 12:10 AM

Hello I have a faulty component on my PCB located in the VGA output, the led of the HDD blinks I tested with a external video card and it works very well, I just want to fix the VGA circuit, and I don't know how to recognize this components, the questions are How can I find similar components? and In what kind of electronic devices is founded? I will really appreciate any help, please check the attached files, thanks.

Attached File  Untitled.jpg   93.74KB   2 downloads



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#2 Joe C

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Posted 15 August 2014 - 05:32 AM

Generally those are not serviceable, they are installed robotic at the factory



#3 Chris Cosgrove

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Posted 16 August 2014 - 07:53 PM

First of all - welcome to BC !

 

Unless you can consider yourself in the 'Expert' class with a soldering iron, Joe C is right - it's not fixable.

 

However, most electronic components carry identification marks on them, colour bands or numbers to indicate value and type markings for other components. If these components are not too badly burnt these should be readable. Surface mount components are available at 'retail', even if for items like resistors this may mean 50 at a time.

 

You say it works fine with an add-on video card. Your best - and cheapest - route is to go that way. Basic video cards are not expensive and at least as good as the on board video, certainly cheaper than a new mobo.

 

Chris Cosgrove



#4 williamws

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Posted 18 August 2014 - 02:24 AM

Thank you for welcoming me!!!

 

Well I am not the best with the soldering iron but I really do a great job with it, that's because I think I'm able to fix it. the only problem is that I don't understand very well how to recognize the name of each component, "Resistor" "fuse" "capacitor" etc etc, so I searched for every code printed on the pcb in google but nothing, any suggest? please check this new pic

 

https://www.facebook.com/photo.php?fbid=10203957545131747&set=a.10201073290067173.1073741836.1615989191&type=1&theater

thank you



#5 Platypus

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Posted 18 August 2014 - 03:03 AM

With damaged Surface Mount Components (SMC), if recognizable values are not stamped on them, the only way to know the proper values is by referring to the manufacturer's schematic diagram. Location codes such as C536 identify only the type of component and which one it is on the schematic. The other consideration is that damage to minor passive components is caused by something else, and if they alone are replaced it is quite likely the same thing will immediately happen again, or the damage will have in fact gone further and replacing them will reveal something like a video chip fault.

 

As others have said, if it works with a video card fitted, that's really the best way around it. It will normally provide better performance than onboard video, and frees up system memory which is also a help to operation.


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#6 kost9

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Posted 11 September 2014 - 05:32 AM

With damaged Surface Mount Components (SMC), if recognizable values are not stamped on them, the only way to know the proper values is by referring to the manufacturer's schematic diagram. Location codes such as C536 identify only the type of component and which one it is on the schematic. The other consideration is that damage to minor passive components is caused by something else, and if they alone are replaced it is quite likely the same thing will immediately happen again, or the damage will have in fact gone further and replacing them will reveal something like a video chip fault.

 

As others have said, if it works with a video card fitted, that's really the best way around it. It will normally provide better performance than onboard video, and frees up system memory which is also a help to operation.

Dear Platypus,

I am new to this forum and based on what you have written, I think that you might be able to help me out with my problem.

I have a device with internal circuitry, at least one component of which(visually) I have burned by accidentally supplying too much voltage and current.

It is a SMC, that says "1R5" on it (I know that from checking the inside circuitry of an identical working device).  Here's an image of it (http://imgur.com/SrmNTc2). I wanted to replace that component manually, but I dont know what this component is (maybe resistor). I definitely need someone's help on this matter.



#7 Platypus

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Posted 11 September 2014 - 07:29 AM

Hello kost9, 1R5 identifies a resistor of 1.5 Ohm resistance. Your image link doesn't work for me, but it could certainly be replaced with one of the same physical size (and resistance of course), so that it will have the same power dissipation rating. If you can solder and have suitable desoldering/soldering equipment, you could buy a chip resistor from an electronic part supplier and make the change yourself, or a helpful repair shop may not charge too much to do it for you. If no SMT components are available locally and there is space on that spot on the board, with some fiddling a normal resistor with wire leads can be adapted to solder onto the SMT pads.


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#8 mjd420nova

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Posted 11 September 2014 - 05:11 PM

I can't count the number of boards that are in my junk heap for these same problems.  Surface Mount Components (SMC) are installed by a machine and soldered by machine in a flood process.  Replacing a single component is very delicate and most often results in a damaged board during the removal of the old device.   If the unit works fine with a video card installed, I go with that as the MOBO needs replacement and can't be repaired.



#9 kost9

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Posted 11 September 2014 - 10:08 PM

Hello kost9, 1R5 identifies a resistor of 1.5 Ohm resistance. Your image link doesn't work for me, but it could certainly be replaced with one of the same physical size (and resistance of course), so that it will have the same power dissipation rating. If you can solder and have suitable desoldering/soldering equipment, you could buy a chip resistor from an electronic part supplier and make the change yourself, or a helpful repair shop may not charge too much to do it for you. If no SMT components are available locally and there is space on that spot on the board, with some fiddling a normal resistor with wire leads can be adapted to solder onto the SMT pads.

Thank you for your reply Platypus!

 

Sorry about the link, these should work now: Burned one http://imgur.com/SrmNTc2  and working one: http://imgur.com/gkZYLwD .  Also, I have a question about the power dissipation rating that you have mentioned, is there a specific rating I have to look for, or do 1.5 ohm resistors come in 1 power rating? (The device itself was consuming 12VDC and about 250mA of current, so 12x.25 = 3Wt power?)

 

Thank you for the reply again!



#10 Platypus

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Posted 11 September 2014 - 11:14 PM

The power dissipation capacity of SMT is set by its physical size (for the same resistor material). I guess from the photo those might perhaps be around 200 mW each, but having the 2 in parallel means they share the current and dissipation equally. Without knowing their specific function, even if they pass more than 250 mA as a startup surge limiter/fusible link, the resulting dissipation will be much less than 400 mW.

 

The combined resistance will also be halved to 0.75 Ohm. So whilst 2 identical SMT resistors could be fitted, a single larger resistor of the lower value could be used. This is not a standard value from the E12 resistance scale, but it's possible either standard value 0.68 or 0.82 would do. But simplest would probably be to solder 2 small (eg 1/4 W) standard resistors across the existing SMT ones.

 

Have you been able to confirm with a meter that the existing ones have gone open circuit? If so there would be no real need to remove them if you can fit standard resistors. On the other hand, if they have got very hot but not failed, that would indicate something else has died first, such as one of the ICs or other devices. Either way, you might still find replacing the resistors could reveal more damage. Hopefully the resistors will have sacrificed themselves and preserved the rest.


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#11 kost9

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Posted 12 September 2014 - 12:50 AM

Thanks for helping me, Platypus.

 

I checked the resistors with my meter and the tone was sounding in continuity mode (across both resistors), I measured resistance and it showed 0.9 ohm for both. So based on your prvious reply, I'm guessing the resistors did not fail (? even though they look like they have been set on fire), meaning some other component did. Also, I forgot to mention there's this terrible smell coming out of the whole device. If that is the case, trying to fix the device myself is probably impossible, since I cant find the component(s) that have really failed.


Edited by hamluis, 12 September 2014 - 01:01 PM.
Removed unnecessary quotebox - Hamluis.


#12 Platypus

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Posted 12 September 2014 - 05:51 AM

Yes, allowing a small resistance for the meter leads, that's what you'd expect to measure if the resistors are still at or close to the correct value. Looks like they got very hot but if the device no longer works, something else has failed. An unpleasant acrid smell often indicates a plastic cased device like an Integrated Circuit, so usually not feasible for you to diagnose and repair.


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#13 kost9

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Posted 13 September 2014 - 02:51 AM

Thank you for your help Platypus!

I appreciate it.



#14 Platypus

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Posted 13 September 2014 - 08:25 AM

You're welcome. :)


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