This is a newer (newest?) revision of the Grappler+ parallel printer card for the Apple II.

Schematic

KiCad Project & all artifacts

The card I have has an official “Orange Micro” sticker on the EPROM and what looks like “3.3” hand-written on it however the EPROM contents contain the version string “3.2”.

This revision fixes a couple issues with the previous revision:

• IRQ support is completely removed to resolve reported issues with some buggy IRQ handling
• Minor timing changes to reportedly fix compatibility with the Apple IIgs

Front Image

Back Image

Updating revision A

The changes from revision A are so minor that it’s possible to rework a revision A model pretty easily; you can compare the schematics (revA -> revC) to see the differences. I don’t have the means to test this but roughly you would:

1. Remove Q1 and R2 completely
2. Replace U10 with a 74LS374
3. Cut the traces leading into U3 pins 11, 12, & 13 so NOR gate U3D can be repurposed
4. Cut the trace leading into U10 pin 11
5. Connect U3 pin 11 to the Apple Bus connector pin 37 (the Q3 signal)
6. Connect U3 pin 12 to U4 pin 8 (the /DOUT_SEL signal)
7. Connect U3 pin 13 to U10 pin 11
8. Install a 100pF capacitor, C8, between +5v and U9 pin 20
9. Update the EPROM with the newer firmware