t looked like a capacitor charging curve. So I replaced the 5V rail psu filter cap and voila: The Roland TR-909 was operating normal again. While I was in here I decided to re-cap the whole PSU, since the next issue wasn't far away. I removed that ugly, corrosive glue and cleaned the pcb. Since the mains voltage (in germany) is a bit higher since the initial release of the TR-909, I decided to move the jumper wire from 220V to 240V.