GEMClub TurboKit Plus Installation

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GEMClub TurboKit Plus Installation

April 25, 2021 | | 2 Comments

Welcome to the GEMClub TurboKit Plus, installation guide.  This guide is currently WORK IN PROGRESS (Updated 16th June 2021 DW)


Back in 1992, GEM (Generalmusic), released the S Series Musicprocessor which proved to be a renowned Synth Worldwide. This was subsequently upgraded in 1994 with the first release of the GEM TurboKit.

This GEMClub TurboKit Plus has been designed to bring life back into both the original GEM S2 and S3 Series. Can also be retrofitted in the S Turbokit Series such as S2 Turbo, S3 Turbo and S2/R.

The TurboKit Software update offers new features and improvements over the original S Series, including:

  • Tone generation: variable oscillator assignment options, two new operating modes (dual oscillator and single oscillator)
  • Polyphony: max. 32 voices
  • Sounds: 500 sounds and 100 ROM performances
  • Sequencer: the sounds can be edited while the sequence is running, LFO can be synchronized with MIDI clock
  • Internal memory: A battery-backed RAM disk can be set up (with additional memory modules)
  • Sample features: Sample Translator integrated into the operating system, import of samples in many formats, Akai multisamples are read (no sound data)
  • MIDI: Compatible with the GM and Roland GS standards

Details of the original GEM TurboKit PCB can be found here

GEMClub TurboKit Plus Installed













The GEMClub TurboKit Plus has all of the above software updates plus the below additional features:

  • Redesigned PCB Layout using surface mount components
  • 2MB (S)RAM Disk is fitted as standard
    • SRAM 2MB = 4 x 4 Mbit (512K x 8bit)
  • Rechargeable Ni-Mh Battery
    • Large 900mA capacity and remotely fitted from PCB, offering much longer SRAM memory Life
  • Ni-Mh Battery charge and management
    • Automatic battery charging and state monitoring
  • Updated Expansion Port for future options (including expansion port mounting hole top of the PCB)
    • By default, the 34 way expansion port is configured the same as the original TurboKit SCSI Port

















In The Box:

  • 1 x GEMClub TurboKit Plus (Fully Tested, OS, SRAM, Battery)
  • 1 x Set of main CPU PCB upgrade components and wires
      • 1 x 3.6V 900mA NiMH Rechargeable Battery
      • 1 x 32MHz HC49S Quartz Crystal PTH (XT2)
      • 2 x 22pF Capacitor PTH (C116 and C119)
      • 1 x 2K2 Resistor (R161)
      • 1 x D72064LM Upgraded Floppy Controller (IC62)
      • 1 x 9 Way Ribbon Cable
      • 1 x 6 Way Cable
      • 1 x Battery Extension Cable
    • Cable Ties (Battery Mounting and 6Way Cable)
    • 1 x Set Wires (Under CPU Board)
    • 1 x Set Foam Pads
    • 1 x Additional set of through hole pins (for alternative installation option)

















This GEMClub TurboKit Plus has been designed to be retro fitted by a electronics engineer, or competent person, into an existing GEM S2 or S3 keyboard.

  • All parts on this upgrade kit are low voltage (maximum of 5V DC), and is so designed to safely take power from the main product DC supply
  • The fitting of the TurboKit does require a level of engineering competency, soldering and cutting of tracks
  • As part of production, this GEMClub TurboKit Plus has been fully tested, prior to packing
  • Neither GEMClub, or the manufacturer DitroniX Ltd, accept any liability, faults or losses, as a result of installing this GEMClub TurboKit Plus
  • Your GEMClub TurboKit Plus warranty may be voided should damage be caused to the upgrade kit itself, due to incorrect installation, or ESD damage

Handling ESD sensitive parts

This GEMClub TurboKit Plus use parts that are known to be sensitive to electrostatic discharge (ESD), or static electricity. This typically relates to components such as the SRAM memory, logic devices, or EPROMs.

  • Whilst every design effort has been included to help protect from ESD, ideally keep the kit in its original protective shipping package (ESD bag), until you are ready to install the kit into the GEM keyboard
  • Make the fewest possible movements with your body to prevent an increase of static electricity from clothing fibres, carpets, and furniture. Prevent the part from touching your clothing. Most clothing is insulative and retains a charge even when you are wearing a wrist strap
  • Should ESD be a concern to the installer, ideally wear an ESD grounded wrist strap against your skin to eliminate static on your body

GEMClub TurboKit Plus Installation

Note: Should you be familiar with the original GEM TurboKit installation, this does differ slightly with fitting the GEMClub TurboKit.  Should you be replacing the original GEM TurboKit with a GEMClub TurboKit, then swapping over will work fine, without any CPU board modifications (other than adding the 6 pin cable).

Important: Ensure the keyboard mains power cable is physically disconnected.

The GEM keyboard mains power supply is not safety shielded and has high voltage parts exposed !!















Top Level Steps:

  • Open Keyboard
  • Remove Keyboard
  • Remove Main CPU PCB
  • Remove Four Components
  • Add Five Components
  • Cut Two Tracks (Bottom)
  • Add Connector Wires (Top)
  • Add Cable Loom (Bottom)
  • Fit GEMClub TurboKit Plus
  • Fit Pads
  • Fit Battery
  • Reassemble

Tools Required:

  • Philips Screw Drivers
  • Nut Spinner or Pliers
  • Fine Side Cutters
  • Soldering Iron (Small Tip) & Solder
  • Solder Sucker (Optional)
  • PLCC Extractor Tool
  • Scalpel
  • Patience – Not Optional 🙂


Detailed Step Guide. Please carefully:

  • Open Keyboard
    • Turn Keyboard upside down on soft material to avoid scratches and remove the 14 screws
    • Beware of interconnecting cables between base and top







  • Remove Keyboard and attached cables
    • Makes it easier to install TurboKit and
    • Ensures CPU board is not damaged when pulled out.





  • Remove Main CPU Board
    • Carefully remove the connected cables
    • Undo the four rear nuts (top of PCB)
    • Slide CPU board out from plastic front holder





  • Unsolder the Lithium Cell Battery (dispose of safely)








  • Remove Resistors R199 and R221
    • Using side cutters














  • Floppy Controller
    • Remove IC62 (WD37C65C) – Carefully!!
      • Using a PLCC extractor tool (avoids breaking the socket)
    • Remove through hole plating around R161, XT2, C116 and C119
      • Using solder sucker
    • Fit R161 (2K2), XT2 (32 MHz), C116 and C119 (22pF)
      • Solder and ensure excess wire is trimmed from below the PCB
    • Fit IC62 with D72064LM
      • Note notch position and orientation (Bottom left of picture)
    • Remove link J6
      • Using side cutters



























































  • 6 Way Connector
    • Solder three wires as shown
      • Yellow, top of D2
      • Red, right end of R182
      • Black, right end if R221
    • Blue and Green are optional
      • Improved Ground and +5V for Future Expansion
        • Blue, J3 Ground
        • Green, bottom (Emitter), of TR19 transistor
    • White is unused
      • Spare rechargeable battery connection
      • Cut off, or tape up or heat shrink to prevent shorting



























  • CPU PCB Bottom Side
    • Cut TWO separate tracks, highlighted below
      • If you cut two lines close together, the copper will lift in-between and you can gently scrape it off with the knife, or hot soldering iron with small tip
      • Ensuring they are cleanly broken and not shorted
      • Using scalpel
      • Be careful NOT to cut too deep into the PCB, or you may damage tracks in other layers














  • Connect FOUR Wires
    • Solder wires as shown
      • Grey (220mm)
      • Red (220mm)
      • Orange (160mm)
      • Yellow (160mm)
    • Ensure no bare strands are shorting to other pins
    • Ensure no splashes of solder are shorting to other pins
    • Optional, Glue under heat shrink to keep in place

























  • Add Foam Pad
    • Under EPROM socket to provide support












Installation alternative comment

As a side note, some people that Gig with the S, have commented that they prefer to take out the EPROM sockets on the main CPU board, and replaced with through pins.  So, the TurboKit now comes with additional fitting options. 

Removing the old DIL32 sockets is very easy with a solder sucker, if this your preference too.  Equally the original GEM EPROM DIL32 sockets are not the best of quality and some have tarnished contacts.


  • Fit TurboKit Plus PCB to CPU Board
    • Plug Cables to PCB
      • Battery Extension Cable
      • Fit 9 Way header Cable
    • Carefully locate the 2 x 32 pin header into the existing EPROM sockets
      • Press firmly to ensure all four x 16 pin headers are level with existing sockets
    • Plug 9 Way cable to main CPU board
    • Plug in 6 Way Cable
      • Hold TurboKit board when connecting
    • Fit Pad(s) over header connector
    • Plug Battery to Extension Cable
    • Cable Tie Battery to Convenient location












































Ensure the header connectors are fully pressed down


























    • These provide short circuit protection and PCB support
    • Cut one pad to angle around 9 way connector (as shown)
    • Some later kits have these fitted as standard











  • Remount CPU board to the chassis
    • Gently tighten the four nuts on top of the board
    • Reconnect all cables
    • Refit the keyboard













  • Fit Rechargeable Battery
    • It can be mounted anywhere suitable.














  • Optional double sided pads can be fitted under the PCB
    • These are not normally required but if the keyboard is moved about a lot, then a good option
    • Can easily be stuck on top the the DAC IC
    • Roughly 6mm gap is available
      • Ensure any pad(s) fitted is thick enough so not to tilt the TurboKit PCB and cause the header connectors (to old EPROM sockets), to pull out













Finally check no loose connectors, parts etc.

Lay top back over, apply power and test that the S (Turbo), boots up OK.

Hopefully all is OK and you can now reassemble the case.



Designed and Made in Great Britain by DitroniX Ltd

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About Author

about author

Dave Williams

Original and sole proprietor of GEMWorks Europe, later renamed to GEMClub - Generalmusic Owners Club.

  1. Dave Williams

    TurboKit Plus Testing

    As mentioned, the TurboKit Plus boards are fully tested prior to shipping.

    The boards are plugged into a test S CPU board, in order to confirm the EPROMS, SRAM and Battery charger are all working OK. The S is booted to a floppy disk. The floppy contents are the copied to SRAM and the S is rebooted. The SRAM contents are loaded and tested. The rechargeable battery is checked to ensure this retains the SRAM memory contents and is charging.

  2. Dave Williams

    Installation alternative option

    As a side note, some people that Gig with the S, have commented that they prefer to take out the EPROM sockets on the main CPU board, and replaced with through pins.  So, the TurboKit now comes with additional fitting options. 

    Removing the old DIL32 sockets is very easy with a solder sucker, if this your preference too.  Equally the original GEM EPROM DIL32 sockets are not the best of quality and some have tarnished contacts.

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