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. This is a common problem with hammer-action weighted key keyboards and is really annoying. The design of the actual keyboard part in here is something that Korg developed called the RH3 that is often disparaged for being particularly fragile and unreliable.

You have to take out a lot of screws to get to the hammers, and everything is slathered in some kind of nasty lubricant that feels like thick Vaseline and smells like a sweaty armpit. I’ve worked on two other hammer action keyboards that had the same lubricant, and I don’t know what it is but I dread encountering it! Anyway, no thanks to the rest of the internet, I figured out that when you find a dropped key, it will have been caused by one of two possible reasons.

  1. Damaged Fulcrum
 hammer fulcrums of Korg RH3 keyboard assembly from SV-1 stage vintage piano
White: damaged fulcrum
Grey: good fulcrum

The first possibility is that the fulcrum of the hammer is damaged. This is most likely to happen to the little hook piece that hooks onto the keybed frame. At left, notice how the circled area on the white fulcrum is shorter and stubbier than the circled area on the grey fulcrum. Losing about 1mm of length from this piece is all it takes to make a key drop, and the plastic is soft and apparently gets broken or smushed easily. Fortunately, the replacement fulcrums I bought seem sturdier than the originals. I got them here from guitar-parts.com

2. Bent hammer

Korg RH3 key assembly hammer
Korg RH3 key assembly hammer

The degree to which a hammer must be bent to cause this problem is so small that it is pretty much visually imperceivable, but if you have a dropped key whose fulcrum seems fine, suspect this problem.  All you have to do is very gently and very slightly bend the two ends of the fulcrum upwards, as shown at left. Check the side to side alignment while you’re at it.

You may wonder why I give this kind of info out here. Aren’t I worried I’m putting myself out of business? But honestly, if I never have to fix this particular problem again, I’ll be happy. That stinky lubricating goo is really hard to wash off your hands.

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