Curious, why glue them at all?

To prevent detachment during transit. Those PCBs are without proper metallized vias so solder is only on one side of the PCB not through the PCB, and it just isn't a mechanically sound connection that way. This is why the glue is used on all the bigger components.

Bondi wrote on 2022-01-20, 19:28:

Opened my SC-55K - no sign of that adhesive at all. According the dates on the chips it was made in mid 98, much later than OP's device.

The ST and karaoke K variants don't have the VRM circuitry in the back that necessitate the large filter capacitor. I only saw these inside the ones with an LCD display.

Tiido wrote on 2022-01-20, 19:34:

To prevent detachment during transit. Those PCBs are without proper metallized vias so solder is only on one side of the PCB not through the PCB, and it just isn't a mechanically sound connection that way. This is why the glue is used on all the bigger components.

no, oscillations make them shake loose and break the solder joint. so you glue them down.

https://youtu.be/1Y2L6QLOi-c?t=339

With these particular devices, those oscillations etc. happen during transit not just normal use where it sits pretty on your (near) prefectly stable desk.
Assembly procedures in factory and actual shipping and handling are the primary sources of trouble with these things and the single sided nature of the boards makes them especially vulnerable and that's why they're glued down and just the few large parts with enough mass to stress out the solder joint.

That all sounds like such terrible design..

appiah4 wrote on 2022-01-21, 09:34:

That all sounds like such terrible design..

I doubt roland or whatever other random manufacturer of the 90s you can think of expected that their devices will still be used 30+ years later 🤣
roland never heard their target audience complaining that their SC devices failed, by the time this happened they all moved to the next and better thing for their work
from a mass production point of view anything that lasts 10 years is more than enough , remember these are consumer electronics and not meant for military use or deep space travel 😉

We are actually lucky that such old things still work - it is expected that some sort of maintenance must be done after 3 or 4 decades
at some point maybe the chips will rot inside and that will be the end 🙁

It make me wonder... I have hardly used (let alone maintained) the MT-32 I bought back in 2009. Is that model also prone to this type of corrosion? Or were they simply built better in the (even) earlier days?

Maybe I should just open it up and take a look inside, one of these days.

appiah4 wrote on 2022-01-21, 09:34:

That all sounds like such terrible design..

Don't psus use glue on caps as well?

I opened my SC-55mkII up and the glue is still kind of pliable and doesn’t seem to have caused any corrosion on the board. Still doesn’t look good and I’ll be scraping it away just in case. I opened it up just after unplugging it and the nearby heatsink is still pretty warm. With my current setup I have it plugged in and in standby all of the time and it’s cooking that poor capacitor. I’ll definitely be putting this on a hard wired switch from now on.