Another Roland TR-909 Analog Drum Machine in for repair. This one is from the producerteam of the group Fragma. I know these guys since years. They told me, that when switching on the 909, it comes to life, functions for half a second playing the crash cymbal and then went dead again. Then the TR-909 waits a few seconds to do that again, and that cycle goes for about 5-10 minutes. After that the Roland TR-909 behaves normal. Measuring the 5V rail quickly showed, that the 5V was low, about 4,3V, but slowly climbing (click to see the Instagram video)
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.
There are lethal voltage exposed in electronic devices. Unless you know what you are doing, don’t try this. If you following along, you doing so at your own risk.
I’m documenting repairs for my reference and yours.
I do synth restorations and repair with a specialty in vintage synthesizers, drum computer and other vintage gear, based in Düsseldorf, GER. Get in touch about your synth situation!