I'm trying to recover an old keyboard (of about 25 years old). It has all circuitry gone in paradise, but it had a midi output and input line. Moreover, its keyboard mechanics and the transducer work properly. I saw with an oscilloscope that the output from the transducer is something that resembles a midi signal, so I connected this output to a standard 5 din connector following the figure 1; then I connected it to the computer through the midi-to-usb converter in figure 2 (soundsation usmi100), alimenting the keyboard once with the original alimentation (the one built into the keyboard) and once with the alimentation pin of the 5 din connector.
The connector works great with an other piano midi output that I tried, but when I connect it to the my old keyboard, it doesn't work: I can see it from my computer and I can work with it, but it doesn't send data. Moreover, to work correctly it should be flashing (with the piano, it flashes!), however, when connected to the old keyboard, it does nothing.
Why the converter doesn't see the input?