I am finishing up building a v1.6 A2VGA card.
Before I call it done I am looking for some advice.
First: There are two poly fuses on the board, mf-500ma Polyfuses to be exact.
Are these needed? Could they just be jumprered? What risks would this introduce?
Second: There is a schottky diode on the scematic and board. No specific values were listed on the schematic. It was suggested in this thread that a BAT85 Schottky would work. I don't have any of those so I am looking for potential alternates but I am not an EE and I am not well versed in selecting diode values, let alone alternative componenets.
From previous project builds I have some
- 1N4148s
- some Zeners (8.2v, 1N4733 5.1v, 6.8v)
- 1N5817 Schottky
- 1N4004
- 1N4001
Thanks
Mark
Could you post a link to the GitHub?
https://github.com/rallepalaveev/analog
I am building v1.6
https://www.applefritter.com/content/getting-your-apple-ii-vga-card-and-running-ralle-palaveev-version
Think this will answer some of my questions. Not the alternative diode queston though.
You can get rid of the fuses and D1 and simply replace them with 0-ohm jumpers, but you need to be careful not to power the Pico while the card is plugged to the Apple II. Without D1 of you plug the Pico to your laptop and JP1 is closed, you will essentially be powering the entire +5V rail of the Apple II from the USB port of your laptop!
Passing +5V on pin 9 of the VGA port was originally a mod I did on Vince Briel's VGA card. It allowed a VGA->HDMI converter to be powered through the VGA port and not to require an external USB cable: https://www.applefritter.com/comment/104763#comment-104763
If getting rid of Fu1, you need to make sure any VGA monitor or adapter you plug into the port doesn't have its Pin 9 connected to ground. Passing +5V on pin 9 was actually part of the original VGA standard, but no manufacturer actually did it.
Reference: https://github.com/rallepalaveev/analog/blob/main/A2VGA.v1.6-hardware/A2VGA.v1.6.sch.pdf
I had also run these questions through Grok in the mean time.
Basically said similar. I jumpered both fuses with a piece of scrap from cut passive component leads and used a 1N4148 diode as an alternate.
I will check the mornitor Pin 9 before I connect it.
One final question. For standard VGA use (just using it for video, no mouse use, etc) I would not jumper JP1 or Jp2, correct?
Thanks for the help! :-)
That is correct, for VGA you can leave JP1 and JP2 open.