I recently got a Super Serial Card and installed it on apple II+. I am now trying to network II+ and MacBook with using modem MGR, but I have a problem. The text entered on the mac is displayed on II+. However, the text entered on II+ side has not been sent to macbook. So when I checked the signals on the card and I found that the TXD signal was not detected.
Next I install the same card on another apple II+ and do the same thing, The card worked fine and communication between computers work perfect.
From these, I conclud that there is a problem with the motherboard of II+.
The cards currently installed in the slot are RAM card(#0), 80 column card(#2), Super Serial Card II(#3), DiskII card(#6) and VGA card(#7). These seem to be working properly.
It would be very helpful if you could give me some advice on what to check on the motherboard.