This custom board update replaces the original 80C31 microcontroller (in the socket) using an adapter board in the Marshall 6100 / 6101 amplifier.
This simplifies the original design with integrated EEPROM for MIDI data and program memory. 
- Maintains the original output latch (74HC574) and opto-coupler (6N138) for MIDI command isolation

- Installation is simple (remove IC301 thru IC304) and install this adapter board in the IC302 socket.

See video demo: https://www.youtube.com/watch?v=wizx0_r7DVs

This update saves the last channel selected (Clean/Crunch/Lead) and restores it at power-on.

- It operates much like the old firmware allowing the users to save different PC MIDI commands for each channel.
- A double flash of all LEDs gives the user better feedback verifying the MIDI command is saved.
- Future updates are possible using the USB-C port on the microcontroller board.

If you are having trouble with your original MIDI circuit, this may help resolve the issue.

Note: Dangerous and lethal voltages are inside of your amplifier. Always have an experienced person work on it.

Designed and Built in the USA.

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