Korg Polysix Repairs

Tonight ive decided its high time that I start on the pile of synths that I have that are in need of repair. In the past couple of years I have amassed quite a collection of vintage gear, and it is now becoming apparent that I need to keep up with the repairs or I'll never have them all fully working.

While I was in between places to live I bought a broken Polysix, it has the typical battery leak damage to the KLM-367A board. The synth came with a bag of parts that should be sufficient to fix it, or so I was told. After pulling the board out, cleaning up the damaged area and inspecting ive determined ill still need a couple more parts. (IC31 socket, R17 resistor array and some thin wire for trace repair)

Here is its current condition:

Ill try to post progress updates and pictures as I go, for now ive got to track down a couple parts.

Edit (8/6/11) - I worked for the better part of this evening on the PCB and it gave me a pretty difficult time. Clearing the old through holes without damaging what was left of the solder pads was just about impossible. This resulted in the replacement IC31 pins not making good contact with the traces below. I went through and wired up all the traces from IC31 underneath the board because of this but after completing my work I still have faults. Ive decided to purchase a remade blank PCB from this site: https://sites.google.com/site/jedjorgensen/klm367a

Once the new PCB and replacement parts come in I will try repairing this thing again, until then onto the next synth.

Gear that needs repair

Realizing that my aging fleet of analog synths mostly all need work, I figured id put together a list to help keep track. All these repairs seemed minor enough at the time of discovery to let them slide for the time being. Now ive fallen behind on repairs and figure its time to start fixing all of them that I can. First on the workbench will be the Korg PolySix, which ill be making a separate post for.

The List

Roland:

• Jupiter 6: voice 6 VCF, env 2 kbd track slider
• Juno 6: PWM adjustment inop.
• Juno 60: 2 memory position switches
• Juno 106: voice 2 VCF, all coatings removed
• TR-606: battery power inop/door missing
• MC-505: screen loose
• JX-8p: aftertouch (custom rackmount?)
• SH-101: pitch bend/mod wheel loose
• SH-09: pitch/vcf bend/mod sliders

Korg:

• MonoPoly: voice 4 tracking
• PolySix: battery damage
• Poly800: battery dead

Moog:

• Micromoog: recap/calibrate

Yamaha:

• CS15: clean/calibrate

Studio Electronics:

• SE-1: MIDI wonky?

The sequencer lives!

This is a long overdue update on the aforementioned Baby 8 sequencer I was building last year. I finished the project in a matter of a couple days and was content enough with it to leave it as is. I still plan to build another with an internal clock and better skip implementation. This one now is kind of finicky with skips, no CV is output when a step is set to skip but the Gate still fires. This is because I didn't include a part of the circuit that would cut the Gate signal when the step is switched off. I was either tired or didn't want to bunch any more wires into an already somewhat clustered space. Anyway I made a video of the thing in action:

The whole project cost me about $200, it can be built for a lot cheaper but I was bored and in a hurry at the same time. That meant I just bought everything at a local boutique store and paid too much for too little. Oh well. Next time, bigger and better!

Down time - One hobby for another..

I wrecked my motorcycle last weekend (5/8/10) and ended up with minor injuries, but I cant work at the moment so I figured id use my down time to catch up on a few things. One being updating this blog I started a little while back. And another is start on a sequencer project I came across, using a 4017 chip to make a simple 8 step CV sequencer. I found all the parts needed at a local electronics store (Baynesville Electronics) and got to plugging away at the bread board. So far ive got the chip hooked up and cycling through 8 steps of LED's, I just need a project box to put the pots in/on so I can wire up the CV side of the circuit. Tonight I burned myself on the soldering iron while being kind of spaced out on percocet so I decided I would take a break for the night.