This Roland TB303 analog synthesizer was given to me for repair with intermittent problems. „It switches on and everything looks to be fine but when you start the sequencer sometimes you can´t hear any sequence/audio.
Intermittent problems are simetimes hard to find. I started wiggeling all connector and connections and while doing that the TB303 sometimes came to life. My guess was to look for a cold solder. I grabbed the schematic and checked for some point where the audio got lost.
Since I knew that, when the fault was there, it was on the mixer as well as on the headphones I could skip this section. Next was to examine the VCA. I poked around that area and suddenly spotted a cold solderjoint.
For me it´s clear that this seems to be the problem I show you a way to verify. You simply grab a metal surface such as a srewdriver or a probe, thats what I did here:
I fixed that by sucking off the old solder and then use new tin and some flux to reflow that solder joint. I verify myself thru magnifying glasses so I could see that my first attempt wasn´t quite satisfying. A second try gives the result I wanted to see. I repeated this with all suspect solderjoints around that area.
Now its playing well, my custumer is happy. He´s such a nice person that he brought some (!) sake to celebrate that fix! Here are my public pics, like always. Maybe it helps someone. Enjoy.