Korg Electribe ESX-1, continued / updated Nov. 2019

11/3/2019: OK, I have yet another update on this!

Unfortunately, about 2 years after I implemented the fix I describe below (debouncing capacitors for each pot, plus a shield) the issue came back!
I wanted to take a closer look through the circuitry with my oscilloscope but did not yet get a chance to because when I opened it up, the issue went away. So I just did my best guess of what might help and packed it up yet again.

I had a good idea of what might help, because thinking more about the symptoms had led me to a stronger idea of what might actually be the issue.

There are really two symptoms:
1. constant random jittering of pot values, which is what people usually focus on
2. the pots can NOT be turned down to 0,  the minimum value anything can reach at full counterclockwise position is 2 or 3 for me usually. Continue reading “Korg Electribe ESX-1, continued / updated Nov. 2019”

Korg MonoPoly

Korg MonoPoly
Korg MonoPoly

This MonoPoly had the worst kind of problem when it arrived: a very intermittent problem. It had a tendency to fade out randomly, and then randomly fade back in. The first day it was here, we ran it for 12 hours continuously without any such incident. It took us a long time to figure out what was going on because it was hard to get it to replicate the problem. Continue reading “Korg MonoPoly”

Korg Electribe ESX-1

“Really, that guy?”: the Korg Electribe ESX-1

UPDATE 8/28: As it turned out, the work described below did not fix the problem with the Electribe. If you are having a problem with jittery knobs and value jumping of your Electribe’s controls, please refer to my later post on the topic for the actual solution!

Just as they say “the cobbler’s children have no shoes,” so also do they say “the synth tech’s gear has 14 jittery knobs and isn’t even screwed together.” I decided to “treat myself” to a couple hours spent working on one of my own instruments yesterday and as a result I probably now have the best-working Korg Electribe ESX-1 in the universe. Continue reading “Korg Electribe ESX-1”

Korg SV-1 “Stage Vintage Piano” – keyboard action repair tips

Korg SV-1 keyboard
Korg SV-1 keyboard

This is a new-ish keyboard that is not a synth, but is stocked with samples of classic vintage keyboards, like the Clavinet, Wurlitzer, Rhodes, Mellotron, etc., and has fully-weighted keyboard action and a little tube preamp. It has 73 keys and because of the weighted keys and thick body material is quite heavy.

My tasks were to replace the USB MIDI jack (a quick job) and fix a handful of black keys that had dropped– they were sitting lower than the other keys and making a clicking sound when played. Continue reading “Korg SV-1 “Stage Vintage Piano” – keyboard action repair tips”

Korg Poly 61

Korg Poly 61 synthesizer
Korg Poly 61

This synth sounds FAT. It’s architecture is really simple, but it sounds really good. I can’t think of any 80s polysynth that is better at making fat, Moog-ish leads and basses.  Six voices of a patch like that sounds absolutely huge.  It has the 4 way joystick shared by the whole Korg “Poly” series which effectively gives you an extra (analog-controlled) LFO. The oscillators have a lot of low end and can sound really fuzzy, like Big Muff fuzzy.  It has a simple arpeggiator that allows you to tell it to run your arpeggio up and down the whole keyboard.  If you trigger an arpeggio by playing several notes in different octaves, it will alternate steps above each of them as it arpeggiates, allowing you to make some complex, interesting sequences. Continue reading “Korg Poly 61”

Korg Delta

Korg delta string synthesizer
Korg Delta

The Korg Delta (or DL-50) is a string synth/polysynth hybrid from the late 1970s to early 80s, from the time when every synth company was focusing on those.  I’ve got an Arp Omni 2 and Roland RS-09 of the same era here in the workshop right now and the Delta is my favorite of all three, even just based on its string sounds (to be fair, the RS doesn’t have a “synth” section).   Continue reading “Korg Delta”