Re: [Oap-discuss] Head Control Module and MCM PCB 0.1" pin connectors

[Dafydd W. <dwa...@us...>]

> 3. I have a question about the capacitors in the head control module...
> What does the phrase "All 0.1uf capacitors tantalum bean" on the
> schematic refer to?   Is this a surface mount capacitor?

No.

> 4. Does the choice to use 0805 and 1206 footprints for surface mount
> capacitors in the MCM PCB cause any problems?  I wasn't sure what
> PCB footprint component to use for cylindrical capacitors.

There's absolutely no reason to use surface mount capacitors on any of the
modules (it just makes the boards un-necessarily difficult to assemble).

I hadn't realized that you had used SM footprints for the caps on the MCM
PCB (I must admit, I thought the square pads looked a little odd, but I
hadn't noticed that there was no hold in the pads).

I would just stick to plain old barrel-shaped electrolytic caps for the
most part (except for the 0.1uF bypass caps, which ought to be Tantalum
bead).

Your best bet, if you're not sure of the footprint, is to just visit your
local Radio Shack or Fry's, and pick up some of the components, or just
mail-order some from DigiKey.

Here's random web site I just googled that has some pics of elecolytic caps:

 http://hometown.aol.co.uk/oldradioparts/capacitor2.htm

They come in two kinds: With one lead coming out of each end (which are
generally mounted "lying down"), or with both leads coming out of one end.
I prefer the latter, because it allows the cap to stand up, taking up less
space on the board.

Here's a web site with some photos of tants:

 http://www.greenweld.co.uk/acatalog/Shop_Tantalum_78.html

Beware that tants ARE polarized, so you should mark the + pad on the PCB's
silk screen layer.

And finally, here's a site with general info about several different kinds
of caps:

 http://www.kpsec.freeuk.com/components/capac.htm