I experienced a similar situation.

In 1993-94 I bought the Roland JV30 with on-board sounds (Roland GS & MT32)
It wss a bit heavy and 39" long...took up a lot of real estate on the mixing desk.

About 3 years ago one of the micro switches was not responding and when I played a note it sounded like a purring tiger....regardless of the note I was playing.

My search began:
I didn't care about on-board sounds because I long ago began acquiring sound modules.
Being the Roland MVS-1/Roland MBD-1/Proteus FX/Roland XV580)
I also have the Midisport 4x4 USB midi patch bay....works great.
I don't think of myself as a keyboard player but I can play well enough on my original songs.

So...I decided all I needed was a controller with a much smaller footprint.
I went with this one and it works just fine....it's USB...it's 70$.
Lots of control/flexibility:
https://www.amazon.com/Monoprice-MIDI-Keyboard-Controller-Pitch-bend/dp/B0160ACM5O/ref=sr_1_1?keywords=Stage+Right+by+Monoprice+49-Key+MIDI+Keyboard+Controller&qid=1581283056&sr=8-1

But...it's a fiscal or preferential call.
Personally, I wouldn't waste time trying to fix something that old unless I preferred tinkering with antiquated gear over song writing/recording....which, I don't. smile

Good luck on your quest.