Roland JDXA (2015-)
Fix of crackles and noises on main output.
I bought a Roland JDXA in 2017 to replace older, and unreliable, gear. The specs looked good. Roland called it an "Analog/Digital Crossover Synthesizer". Four analog voices + a 64 voice digital Supernatural synth. The best of two worlds?
The first thing I noted on delivery was the external PSU. On a PRO's synth? Well, this and the fact that the instrument is almost completely made of plastic isn't really convincing. Compare this to the 80's Jupiters and Juno's, built to last and most still works. Well the sound was good and for a while everything was well.
Then, a couple of years later, when out of warranty, the synth started to emit noises and crackles on the main outputs (and headphones output) when "warm". The installation of a fan solved this until the analog part, suddenly, went completely silent. Since I do not have any schematics (Roland refuses to send any) and the circuit boards are stuffed with mostly small SMT devices, a point to point search with an oscilloscope seemed almost impossible.
Old school testing for errors.
When you are confronted with any misbehaving electronics gadgets, you always hope that the problem is easy to fix. A bad solder perhaps? A loose wire? No such luck? After a thorough and tedious search with the "tools" above, the freezing temperatures suddenly made a change.
At last I found the problem.
The picture above shows (with a red circle, click to download higher resolution image) a small SMT circuit (probably an op-amp, IC10?) on the green mainboard. Use a good soldering tool and heat the pins on the IC to resolder them. The fan was then replaced by a heat-sink as it was no longer needed.
As always! Do not do this if your unit works fine. Hire someone with proper knowledge to do this for you if your unit exhibits similar problems and you are not familiar with electronics work.