I ordered a set of optocouplers the other day and was excited when they finally came in. Unfortunately, I've having a bit of trouble getting them to work. Simple on/off tasks work fine but when I attempt to use it to send MIDI data to an Arduino Uno I get no response. I suspect that the problem lies in the type of optocoupler I'm using. While the majority of projects on the internet seem to use the 6N138 I figured I could swap it out with the similar 6N38. Currently, I think the problem is switching time. The 6N138 is a diode optocoupler while my 4N38 is a transistor optocoupler. But without an oscilloscope I have no easy way to be sure. To complicate things, I can't find much in the way of any circuit using the 4N38 despite it's similarity to other chips. Is it possible to transmit MIDI data with this chip? Should I just buy a different one?
NOTE: VCC is 5V.
EDIT: Corrected part number. EDIT: Specificity. EDIT: Added schematic.