The MAX233 I've used all came in a "skinny DIP" package,
i.e. its like the MAX232 only 4 pins longer [2 on each side].

re: Serial Ground, the Empeg Serial port ground wire is connected to the "Ground" wire in the sled harness so its perfectly ok to leave it connected all the time in your design.

One thing to note that sleds earlier than about serial# 1000 had a problem with the ground wire not being connected in the sled harness.
[my sleds have/had this problem].

So if you use the +12 and ground wires in the serial cable missing this ground wire then your VFD board won't work until you connect your PCB's ground to your cars "ground".


One other point about using the +12 volts on the DTR wire, it is turned off when the Empeg is, so you don't have to worry about it being powered up when your Empeg is off.

Just remember that the +12 volts on the serial line and the remote Amp control line share the same source, so can only sustain 1 amp between them.
For most "correctly done" installations this is never going to be a problem but it is something to watch for.