Tubbutec KAC TM62100 Yamaha SK 30 and SK50D Instruction Manual

Tubbutec KAC TM62100 Yamaha SK 30 and SK50D

The Tubbutec KAC is a replacement for the key assigner chip of the Yamaha SK30/SK50D (YM62100) that allows the user to play the SK30/SK50D via MIDI. It also adds filter, resonance, aftertouch, portamento, and sustain control via MIDI, and MIDI Out. The original behavior of the SK30/SK50D is fully maintained.

Differences between SK30 and SK50D

The SK30 and SK50D share almost the same circuit boards, so this manual fits both machines. Some parts are missing on the PCBs of each version, but the relevant parts are the same. The placement of the MIDI jacks might be different.

Considerations before assembly

Before assembly, you need to remove the mainboard from the synthesizer. Carefully unplug all wire assemblies and refer to the picture provided in the manual to plug the connectors back in the right positions later. Be careful not to damage any of the plastic spacers holding the board.

Soldering Instructions

Soldering the Cutoff and Resonance wires

Plug the 2-pin connector with the long wires in the socket labeled CV on the KAC board. Route the wires to the upper right corner of the control panel PCB. Solder the 100K resistor in a place where shown in the picture. Solder the red wire (Resonance control) to the spot shown. Solder the black wire (Cutoff control) to the spot shown. Secure the wires with cable ties to the wire loom.

Soldering the sustain and portamento wires

Plug the 3-pin connector in the socket labeled CTRL on the KAC board. Route the black and yellow wire to the jack board. The yellow wire (sustain) gets soldered directly to the tip of the sustain jack. The black wire (portamento) gets soldered directly to the tip of the portamento jack.

Soldering the aftertouch wire

To solder the aftertouch wire, you need to remove the top pcb of the PCB stack right of the mainboard. Route the red wire from the CTRL socket to the bottom PCB of the PCB stack. Solder the 82K resistor and the 100nF capacitor in place as shown in the picture. Solder the red wire to the spot shown.

Installing the MIDI sockets

• The MIDI jack assemblies are detachable, so it is possible to mount the jacks from the outside.
• In this case, it is advisable to drill a 16mm hole. You can use the sticker included in the kit to label the midi sockets.
• The sticker is transparent to blend with the existing print. That’s all. Have fun!

Tools you will need

• Soldering iron
• Metal drill 3.2mm (or similar)
• Metal drill for a 15mm hole (stepping drill for example)
• Center punch
• Screwdriver

Included in the kit:

• TM62100 KAC Chip
• 40pin IC socket
• Connection cable assemblies
• 100K resistor for cutoff control
• 82K resistor and 100nF capacitor for aftertouch control
• Midi socket drill guide
• 4x M3 bolt, 4xM3 nut for midi sockets
• Sticker for midi socket labeling

Principle of operation

• The Tubbutec KAC replaces the key assigner chip of the Yamaha  SK30/SK50D (YM62100).
• This enables the user to play the SK30/SK50D via MIDI. It also adds filter, resonance, aftertouch, portamento and sustain control via MIDI, and MIDI Out. Further information can be found in the user manual.
• The original behavior is fully maintained.

Differences between SK30 and SK50D

• As the SK30 and SK50D share (almost) the same circuit boards this manual fits both machines. Some parts are missing on the pcbs of each version, but the relevant parts are the same. The placement of the MIDI jacks might be different.

Considerations before assembly

• You need to remove the main board from the synthesizer. It is also required to desolder the original Yamaha key assigner chip (YM62100, labelled YM621 F) from the main board.
• This needs to be done with care not to damage the original chip and/or traces on the board.
• Proper tools are required to do this and some basic skills in desoldering.
• If you feel uncomfortable to perform this task you might consider reaching out for a technician in your area, or you can contact us.
• A list of synth techs can be fund here: https://tubbutec.de/synth-techs/
• Two holes for the MIDI jacks need to be drilled in the back panel of the synthesizer.

Desoldering the YM62100 chip

• First you need to remove the mainboard from the synthesizer.
• To do so carefully unplug all wire assemblies. The picture below can be used for reference to plug the connectors back in the right positions later. Be careful not to damage any of the plastic spacers holding the board.
• Use a desoldering pump to desolder IC1, the YM62100 chip.
• As this is a single-layer board without plated-through holes this is relatively easy to do, but take care not to apply too much heat and pressure to the solder pads, as this can easily damage the pads and/or the chip.
• After you have removed the Yamaha chip put it in antistatic foam included in the kit to protect it.
• Make sure all solder is removed from the solder pads, and that the pads and traces are all intact.
• Next step is soldering the 40pin IC socket in place, make sure the notch of the socket reflects the pin 1 location of the original chip.
• Install the Tubbutec KAC chip.
• Reinstall the mainboard in the synthesizer.
• Reconnect the wire assemblies, take care to plug them into the correct sockets.

Soldering the Cutoff and Resonance wires

• Plug the 2pin connector with the long wires in the socket labelled CV on the KAC board.
• Route the wires to the upper right corner of the control panel pcb.
• Solder the 100K resistor in place where shown in the picture.
• Solder the red wire (Resonance control) to the spot shown.
• Solder the black wire (Cutoff control) to the spot shown.
• Secure the wires with cable ties to the wire loom.

Soldering the sustain and portamento wires

• Plug the 3pin connector in the socket labelled CTRL on the KAC board. Route the black and yellow wire to the jack board.
• The yellow wire (sustain) gets soldered directly to the tip of the sustain jack, see picture.
• The black wire (portamento) gets soldered directly to the tip of the portamento jack, see picture.

Soldering the aftertouch wire

• To solder the aftertouch wire you need to remove the top pcb of the pcb stack right of the mainboard.
• Route the red wire from the CTRL socket to the bottom pcb of the pcb stack. Solder the 82K resistor and the 100nF capacitor in place as shown in the picture.
• Solder the red wire to the spot shown.

Installing the MIDI sockets

• First place the drill aid for the MIDI sockets on the back of the synthesizer.
• We chose the space between the voltage selector and the Yamaha logo.
• There is enough space but it is advisable to take exact measurements where to place the jacks.
• After you placed the drill aid use a center punch to mark and drill the holes, 3,2 – 3,5mm for the mounting holes, 15mm for the jacks.
• Next step is installing the MIDI jacks. The upper jack is MIDI In (2pin wire assembly), the lower MIDI Out (3pin wire assembly).
• As the MIDI jack assemblies are detachable it is also possible to mount the jacks from the outside. In this case it is advisable to drill a 16mm hole.
• You can now use the sticker included in the kit to label the midi sockets. The sticker is transparent in order to blend with the existing print.
• That’s all. Have fun.

References

• Synth techs | tubbutec

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