Ordering capacitors

[equant]

I want to order caps for several of my Macs. I've managed to find part lists for several of them, but the physical dimensions are almost never given.  How do people order caps (SMD or THT) without this information?

 

[LaPorta]

Some general info:

-Even if the caps have the same rating, using one that is drastically smaller physically, especially of high voltage, will cause heat dissipation issues and likely premature failure. Too big on the other hand will not fit. That being said, they need not be exactly the same size.

-If it looks like a tight fit, I will use my digital calipers/micrometer to get the length and diameter of the part. Most sites show this information when you look up the part. I usually keep this info in a notebook for further reference.

 

[equant]

Thaks for the reply.  It's looking like I'll just have to open up my macs and do an inventory.  Especially with the SMD caps.  I want to make sure the pin spacing is correct, and that everything fits.  For example, with the powerbook display caps, people list values but no dimensions, and it looks to me like the size would be very important since they have to fit into the holes in the bezel.

One more question...  What about hours?  I see on Mouser a lot of SMD electrolytic caps are rated at 1000 hours.  That seems pretty short.  I must be misunderstanding what that value means.  Can anyone clear that up for me; what does that rating mean?  Obviously they can work for more than 4 days.  Thanks.

 

[LaPorta]

I believe it means rated for that number of continuous hours before failure, although I admit I’m not sure and it must be more involved than that. As far as through hole mount, spacing isn’t crazily important as the leads can easily be bent (I’ve had to make some interesting contortions when replacing the 3.9 mf C1 on the early compact Mac analog boards with rectangular film capacitors). The SMDs, yes, make sure, but I’ve noticed that for a given voltage and capacitance, the size varies far less than the through hole models.

 

[Fizzbinn]

I’ve recapped several Mac motherboards (IIsi, IIci, CC, LC III, Q605) now and it seems for the SMD caps the “white” outline motherboard sizes fall into two sizes (lengths) with the pads actually extending ~1mm further out on each side:

~5mm L : 10uf - 16V 

Tantalum replacements size/case code “B”, 3.5mm L

~7mm L : 47µf - 16V, 100µf - 6.3V

Tantalum replacements size/case code “C”, 6mm L

or

Tantalum replacements size/case code “D”, 7.3mm L

I have 2 IIsi’s so I took pictures to show the difference between using “C” vs. “D”:

IIsi recapped with size “C”, yellow, C5,C9,C10,C11:



IIsi recapped with size “D”, black, C5,C9,C10,C11:



At first I found the smaller capacitors to be intimidating but I think they are actually easier (I like having more of the pad exposed) once I got the right tools, materials (flux paste!) and the technique down. (Not going to post cockeyed cap pictures of my first go at this on my LC III ;-) )

 

[equant]

@Fizzbinn Thanks, those pictures along with the measurements and case codes are helpful to see.  I have a IIsi and LC III waiting.