Roland JX-3P PSU repair

In 2016, less than a year into my electronics career, I repaired my dad's Roland JX-3P that had stopped producing sound. After some exploring and some rabbit trails, I determined that a diode bridge had failed from inrush current overstress. I repaired (and, out of necessity, modded) the power supply and it worked, though it is less robust against AC voltage dips and interruptions now.

[@daleharman839]

I would check the power supply first. Look for ac ripple as the DC values may look fairly reasonable.
Replace any electrolytic capacitors. Usually the biggest electrolytic are not the ones the cause the failure. They will definitely give more noise and need replacement, but the smaller electrolytics are often in more sensitive locations, like switching supplies and protection circuits. Most electrolytic capacitors fail open. Few short but they can be found easier, as they may show damage, or can be found with an ohmmeter. Old, dried out electrolytic capacitors are the number one failure in old electronics in my experience

[@chriswilkinson4044]

Hi Mr. Harman, thanks for watching :) Electrolytic caps have caused me issues a handful of times. The most common thing I've repaired, though, is key switches, since my limited repair experience revolves around keyboard instruments.

[@DamianTangram]

This video is great. I have exactly the same issue with my JX3P.
Just one thing was not 100% clear about.
Did you diagnose your issue as being caused by a failing rectifier or a capacitor?

[@chriswilkinson4044]

It was the rectifier that failed. I replaced the capacitors just because they're the fastest-aging part of most electronics, and it's common to replace them in decades-old equipment so they won't eventually leak and damage other stuff.

[@robinsutcliffe-video_art]

@@chriswilkinson4044 the rectifiers are a poor choice in the original design. It's better to use rectifiers with a higher rating, and use a dedicated heat sink for the rectifiers also, they run very hot. It's very similar in the JX8P PSU, which I have just finished successfully rebuilding (replaced all the components) I am now starting to rebuild the PSU for the JX3P, its practically the same design, only with 3 diodes and 3 fuses extra.