Archives for posts with tag: Synth Repair

The guys gave me the go ahead to finish this beast off!

I cut the feeble grey power chord and put a properly grounded IEC socket on the back panel.

I hunted the rest of the dust bunnies and lubricated the faders one more time to make sure they are smooth and travel happily.

I checked out the bottom of the key bed again and tweaked a few key contacts that looked bent or twisted.

I put the felt switch gaskets where they are supposed to be:  someone had put them on the knob pots instead of the switches.

( the pic shows them in the wrong place! )



It’s a rare beast and really is beautiful.  Even with the crazy 90’s fender knobs!


Video Demo from Youtube:

This week i begin working on a Korg 770.  These are beautiful and built like tanks.  Seriously, I’ve never seen so many screws. Nor have i seen a faceplate BELOW the faceplate!  After removing 30000 screws i got closer to the innards.  For this round i wanted to focus on cleaning and lubricating the controls.  The band had mentioned that several keys were not responding well and the portamento controls were not behaving properly.



I suggested a few other improvements to the guys and i will try to complete this this week:

1, the grey power cable on these old Korg boxes is crap. i looked and there’s space to do an IEC socket like i’ve done ::: Korg MS-10 Power Upgrade :::

2, there was a mouse living in there at some point.  i removed a ton of bits from the inside but i would like to go in with a new can of spray air and hunt them all.

3, i did a first run lube of the sliders and pots.  if i go back in i would completely disassemble the whole chassis and get each one from both sides.

4, the knobs are funny but i didn’t put them back on because they are detent-ed inside and i would defer to you guys on how you orient them.  i would try to hunt some old Korg knobs to make it ‘right’

5, the wood sides should be treated or something to protect them,  the wood looks great on the inside.  the outside looks worn.

 ::: IF :::

This Nord Lead 3 has been sitting in a corner for a few years now.  It was abandoned by a tech that was down the hall after the client didn’t want to pay to ship it to a Nord service center for repair.  But that was a few years ago!  Now it’s possible to get Nord parts from third parties like Syntaur!  So for 20$ in parts ( a new data encoder ) and an hour of work this Nord is Back To Life!



Today i started working on a Moog Liberation.  These are very cool.  Kind of a Moog Prodigy, Kind of a Realistic MG-1, Kind of just AWSOME.

This one has aa few very common issues.

1, There’s several sliders that are damaged.

2, The inevitable Moog melty foam inside the control panel.

3, The controller cable is missing.

First off i took the control panel area apart to assess the damage within.  The sliders are easy to damage as they are not attached to the front panel.  They can often be put back together but they will usually not have a smooth glide afterwards as the little plastic tabs or feet that serve as runners on the bottom break off.

The foam can be removed with isopropyl alcohol and just takes patience.  Several treatments are often required to melt it all away.

The controller cable is a standard cannon type connector with 6 pins.  2 are for 15volt power, one is audio, one is CV, one is S trig, and one is ground.

I’m considering painting the body purple…

best color ever!

Part one can be found here:  I’ve been doing some research on this beast and it’s been really hard to track down service info for this model Crumar in particular.  The Crumar Bit 01 is the rack mount version of this box and i have that service manual but it includes no info on how to properly calibrate the oscillators or filter board.  I’m also not sure if the parts naming even matches really because the boards are not identical within each box.

So with some hunting i found that Bob at Tauntek had posted some info on his site about the Bit 99 that was very helpful.  I don’t have a scope here so i am unable to check the digital side but the analog side it starting to make a lot of sense after a few poke and prod sessions with the tweaker!

1, I fixed the velocity sense on the key bed and it’s back to 90% of feeling good.  It’s still a little clunky in spots and i am attributing this to smoker musician damage at the moment.  I cleaned the springs and rails on the key bed with vinegar and it made a great improvement on the keys that were not striking well or without useful velocity info.  I replaced any springs that were distorted or broken with a set from an old deceased mirage key bed.  So all the keys work and behave much better.  It was hard to get the springs soldered into the right position with the right amount of tension on them.  The mirage key bed has little loops that hold them in so there’s no need to solder them.

2, I am still trying to get the scale and tuning of everything right on.  If i get the oscillators tuned nice with each other the pitch bend scales incorrectly between the two voices and sounds bad.  I can get one range ( up or down ) to work but not both together while the oscillators are  scaled properly.  It’s a bit whack a mole at the moment.

3, The mod wheel is working now.  I’m not sure what was up with that before but that gremlin moved out…

4,  All of the filters are matched decently and sound great!  I will do one more round of adjusting once i get a better feel for how it sits best and sounds the most even.  If i under cal the VCA the oscillators sound better but they leak a lot when the key board is idle.  So i tweaked it back until they just barely disappeared.

5, On other quirk is that it seemed like there was some awkward voice stealing or filter triggering problem at first but i realized that it’s only apparent at the upper / lower 1/4″ outputs.  I figured out that the headphone jack actually mutes the other outputs ( much like the juno 106S and the internal speaker muting ) and the jack / switch is dirty and sometimes doesn’t make great contact.  The Crumar Bit 99 sounds really great in stereo mode when the voices are all panning around within chords.

6, I also epoxied the right end of the key bed as it had cracked.  This should help it from getting any worse.


Side note: There is also a soft version of the Crumar Bit series Here:  I haven’t tried it though…

::: IF :::