Confused by capacitors

[Guybrush3pwood]

So my order from mouser came in and I'm somewhat confused. I have to replace 16v 47uf cans and the capacitors I got for that seem correct, but the 6.3v 10uf capacitors I got are...shockingly tiny. I don't get how these could replace a can...I'm not even sure they're long enough to bridge the gap between the pads. Did I go wrong somewhere?



Here's the link to the product.

http://www.mouser.com/Search/m_ProductDetail.aspx?Kemet%2fC0402C106M9PACTU%2f&qs=sGAEpiMZZMukHu%252bjC5l7YT9bxtUWY4CUHZ8MPhV04dw%3d

 

[bigmessowires]

SMD capacitors come in different physical sizes. That's an 0402 size capacitor, which I think is 40 x 20 mils (thousandths of an inch). You can order larger sizes. 1206 is pretty easy to work with.

 

[Guybrush3pwood]

*Sigh* Ok, I didn't know that. What does 10% and 20% and all that mean? Do I need to worry about that?

 

[olePigeon]

I don't think so, not for this application.  You also don't need to worry about polarization as ceramic doesn't have any.  You can also get a higher voltage if those are cheaper.  So long as the volts is the same or higher than the original, you're good to go.

 

[Guybrush3pwood]

Good to know, just ordered a larger size. Thanks guys. Not sure what I'm going to do with these tiny caps.

 

[uniserver]

 

[Guybrush3pwood]

Ok! So I finished my first recap project! My first victim was a 6115CD. A little tricky, but I plugged it in and it seems to be working great! At least it seems to be. My question is, if it failed, how would I know? What should I test for? Thanks!

 

[Guybrush3pwood]

Also, some people in another group are telling me that it was a bad choice to use ceramics capacitors as it creates more electrical noise and can lead to an unstable system. Is that true? That goes against what everyone here suggested.

 

[johnklos]

The % is usually the accuracy of the rating. It's always best to have the same or higher voltage rated capacitors, but ceramics can be more forgiving than electrolytics.

I don't think any additional noise from a ceramic would matter - these are there to smooth and buffer, not to be used for timing, so it shouldn't be an issue. A new ceramic cap is going to be less noisy than an old electrolytic.

 

[Guybrush3pwood]

Thanks! Now how do I go about telling if this worked or not? Just if everything seems to work ok?

 

[Byrd]

I've used those tiny 16V 47uF tantalum resistors in a few repairs, they work fine.  A successful recap usually means it boots reliably, sound is loud and clear, not too many random crashes (although OS 7 does like to crash on it's own accord ...)

 

[Guybrush3pwood]

Hmmm, sound coming out of the built in PC speaker isn't super loud, but it's pretty clear. Not sure how loud it's supposed to be. It's certainly loud enough when I plug it into my monitor. Would they only affect the built in speaker or all audio?

 

[Guybrush3pwood]

Tell me what you think!

http://youtu.be/es9Q-t9J_LE

 

[Macdrone]

sounds normal.  its a small single speaker.  mine are not loud.  

 

[Guybrush3pwood]

Cool! Thanks for lending an ear. Next up, an LC 575, Performa 575 and a Macintosh Classic. Hope it goes as well.

 

[Macdrone]

all pretty simple once you have done one.  Which you have.  Cleaning while caps are pulled is key.  I wash mine bottom shelf in the dishwasher (no soap) after toothbrushing the spots before hand.  The extra hot water running down the board seems to clean spots i just cant get to sometimes where goo slides and hides.

 

[Floofies]

I'm quite surprised by some of the advice in here, especially considering I haven't done that much research myself.

Tantalum capacitors should be at least 2x-3x derated to prevent early failure, if not more due to the violent nature of a failure, which involves thermite. Also, a Tantalum capacitor operating at or very near it's voltage rating will die a lot faster than a non-derated cap. As for line noise due to simply being ceramic (???), unless you're an audio enthusiast that's not something you have to worry about. In fact, the old aluminum drum caps induct more line noise than any small ceramic cap ever can. The tolerance should be within ±10%, which does affect the capacitor's ability to filter pre-existing line noise, and the reliability of it's capacitance. It's a margin of error for the capacitance, so if you have a 47µF cap with ±10% tolerance, the capacitance could vary within +10% and -10% of that rated capacitance.

Oh, and if you happen to do another recap, there's also simple case size lettering... for the aluminum+plastic drums you can use either size D or E (E is the same width/length as a D, just taller).

 

[Guybrush3pwood]

It actually wasn't here, but the vintage computer group on facebook. The conversation went a little something like this:



Kasey Norman also why did you not put down electrolytic SMT caps? 

Like · Reply · 1 · 16 hrs · Edited







Moyke Baud The ceramics were recommended. I was told they would last forever.

I don't know enough about multimeters to use one safely on this. Any other ways to know? 

Like · Reply · 16 hrs









Kasey Norman Ceramics will last longer yes but not forever lol 

Like · Reply · 16 hrs









Moyke Baud Well, ya know. They just have to outlast me.  

Like · Reply · 16 hrs









Éric Bert tantalum is my first choice 

Like · Reply · 16 hrs









Kasey Norman Tantalum is a long life choice but pricier though you would find them in a better fitting package
 
 
Éric Bert i'm not sure that you could put ceramic in replacement of a bipolar electrolytics

 

Like · Reply · 1 · 16 hrs







Kasey Norman you usually can but their is concerns. 

Like · Reply · 16 hrs








Moyke Baud These were the caps recommended at 68k liberation army. I trust their judgement.







Moyke Baud Well I did. wink emoticon Ceramic doesn't have polarity. 

Like · Reply · 16 hrs


Éric Bert oki, you will have surely higher electrical noise in the circuit. This may lead to a unstable computer 

Like · Reply · 2 · 16 hrs







Moyke Baud I think it'll be ok! 

Like · Reply · 1 · 16 hrs









Éric Bert the time will say it 

Like · Reply · 16 hrs








Moyke Baud Indeed!

 

[Guybrush3pwood]

I'm quite surprised by some of the advice in here, especially considering I haven't done that much research myself.

Tantalum capacitors should be at least 2x-3x derated to prevent early failure, if not more due to the violent nature of a failure, which involves thermite. Also, a Tantalum capacitor operating at or very near it's voltage rating will die a lot faster than a non-derated cap. As for line noise due to simply being ceramic (???), unless you're an audio enthusiast that's not something you have to worry about. In fact, the old aluminum drum caps induct more line noise than any small ceramic cap ever can. The tolerance should be within ±10%, which does affect the capacitor's ability to filter pre-existing line noise, and the reliability of it's capacitance. It's a margin of error for the capacitance, so if you have a 47µF cap with ±10% tolerance, the capacitance could vary within +10% and -10% of that rated capacitance.

Oh, and if you happen to do another recap, there's also simple case size lettering... for the aluminum+plastic drums you can use either size D or E (E is the same width/length as a D, just taller).

Oh, and the caps I'm using have a 20% tolerance. That ok?