Tom:
First thing you should do is test the two ports, the PC side and the
Apple II side.  Put both computers into terminal mode.  Use a paperclip
and short holes 2 and 3 together and type.  If you get the characters on
the screen, the send and receive work on that computer.  If both
computers show good transmit and recieve, then it is your cable that is
not quite right.  Of course I'd immediately suspect one of the
handshaking lines didn't get crossed.

If the IIe is actually not sending out, replace the 1488 chip at A6.

Assuming you look at the end of the SS card where the cable plugs in,
right side up, there is a black plug, rectangle 10 pins which I will
number as follows.
1 2
3 4
5 6
7 8
9 0

DB25s are normally numbered front and back, gender is irrelevant.  The
Signal labels assume the SSC is in the MODEM mode.
Apple SSC to DB25
1 brown  1  ??
2 red    2  TX
3 orange 3  Rx
4 yellow 4  RTS
5 green  5  CTS
6 blue   6  DSR
7 purple 19 ??
8 grey   7  GND
9 white  20 DTR
0 black  8  CD

Proper Null modem Wire DB25 to 25
Tx     2   - 3   Rx
Rx     3   - 2   Tx
RTS    4   - 5   CTS
CTS    5   - 4   RTS
DSR&CD 6&8 - 20  DTR
GND    7   - 7   GND
DTR    20  - 6&8 DSR&CD

Proper Null modem Db25 to 9
2   - 2   RX
3   - 3   TX
4   - 8   CTS
5   - 7   RTS
6&8 - 4   DTR
7   - 5   GND
20  - 6&1 DSR&CD

Thankx,
Ed
eeastmanNO@SPAMapple2.com