This Korg synthesizer came in to the workshop for repair with a jammed mod wheel and missing headphone jack. It appeared that the unit had been bashed during transit. When the mod wheel was moved it only went about 25% of its travel and started scraping. For sure it seemed that the mechanism was being impeded by another object.
The Korg MS2000 is a digital polysynth from Korg who happened to have made some classic syths down the years. This particular model has made it on to plenty of hit records. If you were in to trance in the late 90s, early 00s, you probably heard the sounds of this synth on absolutely tons of records. Being as it is now 2017 it is not too far off from being a vintage synth, so it was with great pleasure that I resurrected this beast and restored it to active service.
The first thing to do was take it apart carefully and ensure no wires were snagged. Sure enough as the casing came apart, the clank of an object hitting the metal case told me something had come loose. It was the headphone port. As this had come out from under the mod wheel, it had unjammed the mechanism and part one of the job was done.
Replacing headphone jack
As you can see in the picture, the protruding section of the headphone port had snapped but the contacts were intact. Before attempting any kind of repair you must ensure that the pinout of the replacement part matches that which you are replacing. I have come across audio connectors before that have opposite pinouts on the hot and neutral. The upshot of this is that if you replace this part then the stereo image will be inverted. This means that any panning effects will come through the opposite side of the stereo field.
The easy way to prevent this from occurring is with a simple continuity test. Essentially, you need need to cut a stereo TRS jack lead in half so you have three wires. You will have a twisted pair of insulated wires inside a screened sheath. This sheath is the ground and the two wires will go to the tip and ring
It is simply a case of identifying which wire attaches to the tip (red in this case) and then you can continuity check the pins. It is simply a case of ensuring the tip is linked to the identical pin when you test the replacement part and the old one.
When desoldering on small fragile boards you don’t want to overheat the pads or else the traces can become damaged and lift off the board. I always tend to use a little flux when desoldering and make sure the iron has been tinned. You want to melt the solder quickly and get it off the board asap. You should always make sure you clean around the pins with desoldering braid afterwards to ensure that the new part will drop in to the same holes. You should also remove any flux from off the board as it can corrode the solder.
I tend to let the flux dry off and crystallise, and then scratch it off with a chisel tip. Then I just use an old toothbrush to get rid of the debris. Then I clean it off with acetone and cotton wool buds, ensuring that there is no cotton debris left on the board as it may cause a short.
After it was all soldered up, I rebuilt and tested it, the synthesizer repair was all good and then I could have some fun playing it. I was going to try and record something for the blog but after hearing one of the patches, I immediately thought of the breakdown in PPK “Resurrection” so thought I may as well let you enjoy that!