Hi all, I have an Apple IIc that seems to have the serial port timing issues described here:
I found this post here on apple fritter (many years old):
Looking at my own board I can see that it does not have the 1.8432MHz crystal installed it also does not have any indications on the board for an optional installation of one.
I am experiencing the serial port timing issues, for me ADTPro works just fine but when trying to use a terminal emulator (any terminal emulator) and regardless of what it's connected to (rs232 wifi adapter, raspberry pi running tcpser, a PC running tcpser, or even just another PC with a terminal emulator running on that) I can only get it to work at 300 baud (or below)
I have tested my serial cable to see if there's any bad connections and it all seems fine so given all of this it seems like the serial port timing flaw is the culprit.
I went ahead and did this mod by cutting the trace going into pin 6 of the "ser2" (6551) chip and soldering the crystal directly onto the legs of the 6551 (pins 6 and 7). using a little masking tape to make sure the crystal doesn't short out anything on the board.
Well the good news is I didn't break anything the bad news is nothing has changed behavior wise. I still can't get a serial connection above 300 baud. ADTPro (using same serial connection) still works fine. I'm having a hard time finding anyone who has tried to do this mod, it seems as long as people can run ADTPro and get Oregon Trail to work they're happy, well I want to do BBSing on this thing so for me I want to pursue it further.
Has anyone actually attempted this fix? Any advice?