Luís Marques

Arcade MegaWing: Diodes and capacitors on VGA

3 posts in this topic

 

Hello,

In the Arcade MegaWing schematic each VGA color component has two diodes and one capacitor. Could anyone clarify the following?
 
1) what are the values of these diodes and capacitors? the schematic doesn't say, it has only a "BAV199" marking
 
2) In the image <http://papilio.cc/images/Arcade_MegaWing1.jpg> I see empty soldering pads near the VGA connector, so I guess the diodes and capacitors were not actually installed on production boards, were they? I guess they are not essential, since the LogicStart MegaWing doesn't have them.
 
3) Essential or not, what is the purpose of that part of the circuit?
 
Thanks a lot!

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AFAIK the diodes are just for protection [to make sure we don't kill the VGA monitor], and the caps (which should only be a few pF) are part of a low-pass [although HF] filter. Jack should have more details.
You can perfectly live without them, though.

Alvie

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Hello Luis,

When we first developed the board we put them on just in case they were needed but we never ran into any situations where they were. We left them off all VGA variations designed afterwords. I don't even remember the specifics that was so long ago...

Jack.

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