Hiya kur4o,
The max 233 is basically a 232 but has internal caps. To me the key is the 7407 and although it is called an inverter, it basically "cleans" the signal. As mentioned, the design I did back in the 90's works flawlessly on 160 to 255k, even with clock jitter. I just want to make something more current using USB. I'm not quite sure what it will take and based on what you said, my memory is coming back to my thoughts back then. Wish me luck