GrapplerMinus has been released
We haven't posted it on this blog, but we have released a card called Grappler Minus. Please read Call-A.P.P.L.E. Mag for the approximate contents. There was no problem when using our SPIISD. Worked pretty well in the Aplle IIe and II plus. but Wing Yeung pointed out a timing issue with him Mfa2 Workshop's wDrive.
https://ct6502.org/product/wdrive/
Resolved timing issue when using WDrive
Our simplification of the Grappler Minus was simply removing unnecessary ICs and capacitors, but it was basically based on Brad Bell's schematics. There are several points that were the key to unnecessary ICs, and the next PCB will include updates for them, but this time we suggest more simpler fix.
I don't own wDrive, so these are supervised by Wing. He kindly gave me fixes and advice regarding my device.
Only one part of the bridge needs to be modified
1，This time there is only one modification. We want to pull up (hi) pin 10 of 74LS279 located in U2, so connect pin 12 and pin 14 of 74LS02 located in U3, which is also connected.
Pin14 is +5V, so be careful not to touch it with other pins. Please make any modifies at your own risk.
2，Normally, I think the above method is sufficient, but Wing points out that his Clone IIplus was insufficient and recommends the following additional modifications. *not always necessary
Remove the 100pf capacitor of C6 and connect it to pin 1 of 74LS00 of U1 and GND.
Add a new capacitor 100pf to pin1 and GND, LS00 of U1 without removing C6.
This is a cap that existed in the genuine GrapplerPlus, but it was placed near an unnecessary IC, so I removed it due to design reasons. It seems more stable if it exists. C6 seems to be fine with or without the capacitor added by Brad Bell.
Future actions
Newer revisions of the PCB will include a modification similar to this, but one that makes more sense. It will be updated to Github soon, stay tuned!
Big thank you to Wing Yeung!