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.

Great work!
I am considering to buy a sc-55 mkii
But I am not sure the jump wire on the board(which are three wires connect chips and board) is normal.
Are those jump wires existed originally or it is some modidy?
Thanks!

My mkII is a first revision. If the bodge wires don't exist, the you probably just have a later one where it isn't needed.

My mkII also has some quirks that don't exist with my SC-55. I only have this one mkII unit, so I don't know if it was caused by the damage to my PCB, if it was fixed with later releases, or if they're all like this.

Re: Does anyone else have any issues with the "MIDI IN 1" socket on their SC-55mkII?

https://sound-au.com/articles/yellow-glue.htm

It never occurred to me to test this crud for electrical conductivity. I would be interested in the results if anyone ever comes across this stuff in their electronics.

There's quite a Yellow Glue rabbithole, once you start looking around and researching.

To name just one example, last year some people started seeing issues (of the fiery variety) with certain UPS models:
https://www.reddit.com/r/homelab/comments/voy … cd_fire_hazard/
https://www.synoforum.com/threads/beware-your … d-burn-up.9149/

Which, when taken apart, was shown to use the Yellow Glue, highly likely the fire cause:
https://www.youtube.com/watch?v=9gqBzLNMFe4&t=647s
https://www.neowin.net/news/beware-your-cyber … -could-burn-up/

A consensus seems to be that, with this glue, the older, the more conductive. Not in a linear manner, obviously, but as a general trend. So it has the fun trio of Instability, Conductivity, Flammability. Add in some Corrosiveness, for extra lols. It is also inconsistent between individual machines, because it seems that the workers who add the Yellow Glue do not always add it in the same locations, from week-to-week or shift-to-shift. So it is truly a lucky dip, to some extent.

As I have seen myself, and discussed in the Check-your-SC55-battery Thread (quite some time ago), even in a Sound Canvas the Yellow Glue can cause a momentary flare-up of fire, likely through some combination of age, heat, and conductivity.