6551 board schematic - capacitors not on schematic?

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Lee Adamson's picture
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6551 board schematic - capacitors not on schematic?

Hey folks.  :D  I am getting ready to (try to) assemble a 6551 board to interface to the Rpi, since I have no super serial card and the A2pi board is out of stock.

 

So, on the schematic for the A2pi here: http://schmenk.is-a-geek.com/wordpress/?p=88

 

... I see no capacitors.  However, looking further down at the photos of the device on perfboard, I see two capacitors soldered on there.  I also see them on the commercial board here: https://www.ultimateapple2.com/catalogzen155a/index.php?main_page=product_info&cPath=1_31&products_id=126 and here (although there is only one on this board): https://www.callapple.org/hardware/ultimate-apple-ii-announces-last-apple2pi-run-for-2017/

 

I assume these are just decoupling capacitors for the ICs?  But they are not very close to the ICs on the prototype......  If so, what values would be appropriate here?  100 nF?

 

Sorry for the dumb questions.  I know a bit (enough to get in trouble, haha) about digital logic in theory, but I'm fairly ignorant when it comes to implementation.

 

Thanks!

macnoyd's picture
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Use a 0.1uf decoupling

Use a 0.1uf decoupling capacitor across each IC.  (there are 2)

Lee Adamson's picture
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Thanks!  :D

Thanks!  :D

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