At 22:23 -0600 8/6/09, Sterling Jacobson wrote:
>Do you have a good place to get the tantalum caps?

The ones I have came from DigiKey <http://digikey.com>, typical part number 
495-1539-1-ND. They have just about everything but there are minimum order 
problems. Mine were purchased from them in reels of 1500 for automated assembly 
on other projects and It's not likely that you would want to do that. Jameco 
and All Electronics are worth a visit to their web sites.

I believe all of the other capacitors, beside C6, are just distributed filters 
on the +12 or +5 volt power distribution system. Their capacitance values are 
not very critical and in general bigger is better. Tantalum caps have better 
high frequency performance than aluminum ones so effective series resistance is 
not anything to worry about.

The aluminum caps that Apple used are all the same capacitance with a 16 volt 
rating. That probably made sense at the time for inventory purposes but the 
caps on the 5 volt line can be rated at 6.3 volts and the physical size and 
cost go down if you do that. The trick is to find caps that fit on the surface 
mount pads with access for a small soldering iron.

Now you ask which caps are 5V and which are 12V.  I'll get around to figuring 
that out right soon now. I'll start with an ohmmeter on a board from which the 
caps have been removed. Right soon now. . .

Remember that electrolytic capacitors are polarity sensitive. They are labeled 
but sometimes one has to read the data sheet to figure out what the bar or the 
sloped corner means when the devices are tiny. If you have only one motherboard 
take a picture of it before you start cutting things off.

Someone was advertising capacitor sets on this or perhaps another list. 
Archives are good.
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