Hey there Andrew - okay, here’s an update, as requested. There’s quite a bit of info I’m sharing here, because I couldn’t find it ANYWHERE on the internet. It took LOTS of research to figure it out.
I ended up diagnosing the problem as a faulty connection between the ribbon and PCB gold leads, if that description makes any sense. By squeezing the gold leads with my fingers, I was able to get the lines to go away. Now for an embarrassing admission: I attempted to just barely heat up the leads to solidify their connection to the PCB, and I almost instantly melted the ribbon cable. I had the PCB taped off with painter’s tape, but I didn’t realize that the plastic ribbon is also connected to the gold leads (duh!). I did all of this with the unit powered on, and instantly blew the fuse in the power supply. I’m sharing this so all of the other newbies can learn from me and avoid this idiotic mistake. Here’s the replacement fuse for the power supply that I bought, and it’s working well:
Pack of 5-2.5A Glass Fuse (GMA), 250v, 5mm x 20mm (3/16" X 3/4") Fast Blow (Fast Acting) Amazon.com
I still have an interest in building an updated LED display, and I was able to find out from an obscure Russian forum (thanks to Google Translate) that the display is driven by 2 Epson SED1565 drivers/controllers, those 2 little rectangular chips on the ribbon. Just a random piece of info for you.
But, until that awesome day of discovery, I caved and just bought a beautiful used display pulled from a Korg Triton LE from eBay (would have gladly purchased from Syntaur if it had been in stock). It works perfectly. I pulled the glass display out of the black plastic casing and gently inserted it into the Karma’s original white plastic casing. The LED lighting on the Korg Triton LE comes from a single bulb that is dispersed by the design of that black casing. The Korg Karma is much better as it has around 40 small amber colored LED’s on a PCB that light up the display quite evenly. Just know that there’s a little more to it than just plugging in a new display if your new display does not come from a Karma.
I also upgraded the floppy drive to the Gotek SFR1M44-U100K, purchased from AliExpress for $15.
US $15.03 41％ Off | SFR1M44-U100K 3.5" 1.44MB 1000 Floppy Disk Drive to USB Emulator Simulation For Musical Keyboard 34pin Floppy Driver Interface
https://a.aliexpress.com/_d7R4Aqm
I had purchased new pots for the joystick, but found that DeOxit d5 spray fixed up the originals perfectly for me. Nonetheless, the pots I bought look exactly like the originals. All of the knobs on the Karma use these.
US $4.99 | 1pcs/lot RK11K1140A9L 500 Electronic Tremolo Wheel Potentiometer 4 Pin 103 Speaker Volume Size Adjustment Knob Switch ALPS
https://a.aliexpress.com/_dSX3bZC
The joystick and knobs were very stiff, and several of the buttons required a bit of pressure to get them to respond. I took the entire keyboard apart and sprayed DeOxit d5 (BIG SHOUT OUT TO SAM MIMS!!!) in all of the knobs, buttons, and the joystick potentiometers to get them working again.
I manually adjusted the aftertouch module gain and offset settings to get that feeling much more responsive when I play the keyboard.
All in all, this keyboard plays like a dream, and far better than it did when I first got it. And… the best part is that I got this synth for free, long story. I am thankful to have a keyboard that is FULL of nostalgia for me!!! Here are some pictures of the final product.
I cannot thank Sam Mims enough! I watched all of his videos restoring synths and they motivated me to try it out. It was a basic part swap out and a failed screen repair, but I still came out ahead, so I’m happy. I learned A LOT through the experience. And I read that Sam played keys for Richard Elliot. I’m a sax player and used to listen to his CD’s all the time in high school. So cool.
If you or anybody else figures out how to make a more modern LED display, please share, as I would love to take the upgrades on this synth further!
