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Back Slot Adapter for Yamaha CX5M and similar computers

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BSA - Back Slot Adapter v1.0
Copyright (c) 2019 RBSC
Last updated: July 26, 2019

WARNING! To avoid damaging your MSX never insert or remove the BSA (back slot adapter) when a computer is powered on!


The device is the simple adapter for the back 50-pin MSX slot. It is designed for Yamaha CX5M and similar computers that have
the back slot formed as the extension of the motherboard. The adapter converts the back slot into the normal 50-pin MSX slot.
So any MSX cartridge can be used with a computer via the BSA.


By default the CX5M computer has the special cover that limits access to the back slot. This cover needs to be removed before
the BSA can be installed. Remove the cover to reveal the back slot compartment. The BSA must be plugged into the back slot
compartment until it is fully inserted and until touches the computer's case. See the corresponding pictures.

After the BSA gets inserted, a cartridge may be plugged into the BSA's cartridge slot. Please make sure that the computer is
powered off before inserting the BSA and/or a cartridge.

When removing a cartridge, please hold the BSA by its case to prevent it from being removed from the computer's case. If the
cartridge can't be easily removed, then first remove the BSA from the computer and then remove the cartridge from BSA's slo..


The model of 3D-printable case is provided with the project. The parts for the case must be printed with 0.2mm layer height
and with their open sides facing upwards. The pin and the 2 feet must be printed vertically and then glued into/onto the case.
Brim is recommended for all models. The supports must be at 20%. The infill must be not lower than 25%. The sturdy PLA is
recommended for the case.

The cover is attached to the case with 4 conical head screws (3.0mm x 20.0mm). Shorter and longer screws must not be used. The
screws could be bought in any decent hardware store.


The BSA cases are usually printed in black plastic. So it's recommend to do the laser engraving of the RBSC's logo and the
device's name. The image for laser engraving is included. The recommended width of the engraving should not exceed 40mm. The
recommended depth of engraving should be 0.15mm.


The board inside the case may wobble a bit. This was designed like that on purpose. Please do not try to fix the board firmly.
Such wobbling makes the insertion and removal of device safer.

The case of the BSA is normally made out of PLA plastic that is rather fragile. So when disassembling and reassembling the
case please do not tighten the screws too much or you risk to damage the threads inside the screw holes. If that happens,
fixing the problem would require inserting a few thin threads of PLA into the hole before using the screw again.


The RBSC provides all the files and information for free, without any liability (see the disclaimer.txt file). The provided
information, software or hardware must not be used for commercial purposes unless permitted by the RBSC. Producing a small
amount of boards for personal projects and selling the rest of the batch is allowed without the permission of RBSC. Printing
of cases is allowed without limitation.

When the boards and 3D models are used to create alternative projects, please always mention the original source and the

Contact information

The members of RBSC group Wierzbowsky, Tnt23, Ptero, Pencioner and DJS3000 can be contacted via the MSX.ORG or ZX-PK.RU forums.
Just send a personal message and state your business.

The RBSC repository can be found here:

The MSX-related 3D models published by RBSC can be found here:

-= ! MSX FOREVER ! =-


Back Slot Adapter for Yamaha CX5M and similar computers






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