What can cause a capacitor to blow on an IC?

Soldato
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My knowledge of IC's is limited. I have the tools and knowledge to replace individual components though.

Mum has a really old Kenwood food mixer, very strongly made and until yesterday had worked fine.

Apparently it started smoking loads.

So I took it apart and the motor looks fine, had a look at the simple IC and two capacitors look blown, well they are blown. Literally.

One is 0.1 x 10-6 F and one is 0.15 x 10-6 F.

How much would these components cost? How likely is it that other components have been damaged (there are not many of them!)? What is the likely cause of them failing?

Regards,

Chris
 
Associate
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If its old old age will make components fail normaly due to build up of crud but electrical items all have a shelf life
 
Soldato
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being soldered on backwards is always good for blowing up electrolitic caps
that or runing at too high a voltate etc will always cook any IC
 
Soldato
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VeNT said:
being soldered on backwards is always good for blowing up electrolitic caps
that or runing at too high a voltate etc will always cook any IC

Mum said the mixer was running on max when it occured.

I think I will get a pic of the IC to assist in ordering the correct parts.
 
Soldato
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If I'm not mistaken, the caps are used to provide a little additional power to help the motor start from a dead stop. If they've overheaten, the motor itself is probably getting bound up. At 20 years old, that doesn't surprise me.

You could replace them for a couple quid, but you'll have the problem again very soon. Like Phnom_Penh said, best just to get get a new mixer.
 
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dude....

turn the power supply on after your a good metre away, youll be covered in capacitor inards (paper/foil or liquid and metal dending on the cap)


edit: after my electronics exam tomorrow i may celerbrate in a rather relavant way and video it ;) - depends if i can get a decent power supply though, screw using mains, last time i did that......
 
Soldato
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Just had the motor apart and it looks fine. It's doesn't even looked used and moves very freely.

The cake mixer still actually works.

I have been chatting to Adam on MSN and have sorted out most of what I need so going to get the parts (cheap as chips) and replace them. Then see how it goes.

However, 2 of the capacitors we are unsure on.

We think they are 25 pico Farad (x10^-12 ???)

Anyway, if you could take a look at this pic and let me know what you think they are. Cheers!

cap.jpg
 
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Associate
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The 250 is the clue... there's no standard for capacitor labelling so not sure what value it is. Usually they are in uF of pF though. The part behind the capacitors is a crystal oscillator though, resonant frequency of 3.8MHz.
 
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Associate
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0.15uF @ X means that at the resonant frequency, the oscillator will be a capacitive load. Not especially important to you, but necessary to know when you're designing a circuit incorporating it.

Best bet for replacing the crystal (if required) is to take that component to a high street electronics store and see if they can match it.
 
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