Korg Poly-61

This gem from the golden age of Synth is the Korg Poly-61.  Which, according to Wikipedia, was Korg’s first ever “knobless” synthesizer.  And don’t let appearances fool you. Although this beauty looks digital, the Poly-61 is still an analog beast; and makes use of digitally controlled analog oscillators (DCO’s) to produce musical magic.

A little backstory… My wife is a Music Teacher.  And most of my family members are at least semi-musically inclined… Except me… I can’t play jack… But if it’s got wires and screws, well now, that’s right in my wheelhouse.

The Korg came to me via a friend/co-worker that picked up a pair of them off some guy on Craigslist.  It was known up front that 1 of them was in “quasi-working” condition, and the other was totally dead.  Luckily, the  “partially working” unit seemed to work just fine.  Or at least well enough for him to play around with…  The other unit was in fact completely dead.  So he offered to give it to me as a gift for helping him mod/re-wire a bunch of guitars previously.  I happily accepted, and thought it would make an awesome present for my wife and son(since she’s insistent on him learning the piano 1st anyway).

TL;DR….  It was horrible in there…. But it does “technically” work now….  Mostly…. kinda/sorta….

Where to start??? 

1. As I came to find out, a lot of these older Synths suffer corrosion damage from battery leaks; and this thing is no exception.  The primary CPU Board had massive amounts of corrosive damage. Circuit traces completely eaten away; legs of capacitors, resistors, and various IC’s all corroded to the max, or gone completely.  One of the primary ribbon cable connectors, which I originally assumed had been desoldered, was in fact completely eaten away.
2. It was apparent that someone attempted to fix it at some point in the past.  There were some obvious mods done to integrate a more modern CMOS/CR2032/Coin cell battery to replace the original NiCad.  There was also a bunch of crazy homemade jumpers all over the back of the board. (Side note… there are still a bunch of crazy homemade jumpers all over the back of the board, but now they’re mine… lol)
3. Here’s where it gets real bad…  After the repairs/mods were unsuccessful, it was obviously scrapped for parts. Can’t say I blame them, the thing was trashed. It was probably used to fix the other “semi-working” one.  Regardless, it was missing quite a few components, as well as 3 of the primary cable headers that weren’t damaged by corrosion.
4. Uncle Tim to the rescue!!! Luckily, I have an Uncle Tim.  If you don’t have one, I highly recommend picking one up somewhere.  Why you ask??? Well because Uncle Tim happens to be an electronics nerd AND an audio nerd.  And in particular an Old Audio nerd.  Not saying he’s old, just that he likes old audio equipment.
5. After a day spent in the lab with Uncle Tim, with a brief hour or so “break” to help him run some new hydraulic lines on his ancient Ditch Witch(it’s like my Pops always tells me; when it comes to friends and family… always work for “favors”); I had a preliminary parts list.  And he confirmed exactly what i didn’t want to hear… I was going to have to re-trace/jump at least a quarter of this thing, on top of replacing all the missing/corroded components; and even then, there was no guarantee it would work…

Shout out to NTE Cross Ref, Newark/Element14, Mouser, and the multitude of scoured forum and blog posts dedicated to the Poly-61.