Commodore 64 – 250407 – MELIUS Rev 1.1

Commodore 64 – 250407 – MELIUS Rev 1.1

$25.00

Here’s your chance to own a brand new Commodore 64 – MELIUS Rev 1.1 main board. The revision is 250407, Artwork 251137.

Project MELIUS is dedicated to improving the original Commodore 64 while staying as true to the original as possible.

This first iteration of project MELIUS boards features the following improvements:

  • RF Modulator Bypass Circuitry – This modification allows you to be free from the RF modulator component by soldering a handful of components to the board which will bring you an improved quality video signal. You can also choose to use the original RF modulator instead. Your choice.
  • EEPROM upgrades – The Basic, Kernal and Character ROM’s have been replaced with 27C512 EEPROM’s. This means that you can burn a ROM and directly plug it into your C64’s mainboard. What’s even better is that because the 27C512 have 64K of space, you can store up to 8 ROM images for both Basic and Kernal ROM’s and up to 16 variations of the character ROM and then quickly select between them by moving around some jumpers.
  • Connector Footprint Updates – This will help with hunting down various connectors for the IEC, A/V and power ports. Especially the power port connectors. Finding these with the 5mm pin spacing for the ground shield is very difficult. This allows you to easily pop in modern replacements.

Revision 1.1 builds upon these modifications with the following:

  • RF Modulator Bypass Circuitry – The first revision had a footprint issue for the 2 transistors used in the circuit. This revision corrects that error.
  • Memory – The existing layout of the 8 4164 DRAM chips has been modified to the following:
    • 2 41464 DRAM chips to provide legacy support and maintain a small footprint.
    • A modern SRAM replacement circuit has been added that can be used instead of the 2 41464 DRAM memory chips.

This is a first batch run. It just happens that my first batch of boards were 100% functional and I have a surplus so I decided to sell them.

Out of stock

Here’s your chance to own a brand new Commodore 64 – MELIUS Rev 1.1 main board. The revision is 250407, Artwork 251137.

Project MELIUS is dedicated to improving the original Commodore 64 while staying as true to the original as possible.

The first iteration of project MELIUS boards featured the following improvements:

  • RF Modulator Bypass Circuitry – This modification allows you to be free from the RF modulator component by soldering a handful of components to the board which will bring you an improved quality video signal. You can also choose to use the original RF modulator instead. Your choice.
  • EEPROM upgrades – The Basic, Kernal and Character ROM’s have been replaced with 27C512 EEPROM’s. This means that you can burn a ROM and directly plug it into your C64’s mainboard. What’s even better is that because the 27C512 have 64K of space, you can store up to 8 ROM images for both Basic and Kernal ROM’s and up to 16 variations of the character ROM and then quickly select between them by moving around some jumpers.
  • Connector Footprint Updates – This will help with hunting down various connectors for the IEC, A/V and power ports. Especially the power port connectors. Finding these with the 5mm pin spacing for the ground shield is very difficult. This allows you to easily pop in modern replacements.

Revision 1.1 builds upon these modifications with the following:

  • RF Modulator Bypass Circuitry – The first revision had a footprint issue for the 2 transistors used in the circuit. This revision corrects that error.
  • Memory – The existing layout of the 8 4164 DRAM chips has been modified to the following:
    • 2 41464 DRAM chips to provide legacy support and maintain a small footprint.
    • A modern SRAM replacement circuit has been added that can be used instead of the 2 41464 DRAM memory chips.

This is a first batch run. It just happens that my first batch of boards were 100% functional and I have a surplus so I decided to sell them.

I am planning on continuously improving this board.

The primary difference between these and the production boards will be the finish.

These have a finish known as HASL which is a tin / lead plating on the copper layers and can wear down over time if exposed to excessive friction, mainly the user and cassette port. The production boards will use a finish known as ENIG which offers a flat surface, longer shelf life and is also lead free and RoHS compliant.

Don’t miss your opportunity to own 1 of only 5 in existence of an official DIY Chris C64 250407 MELIUS Rev 1.1 first ever in existence. Who knows, I may become famous one day hahaha..

Weight 8 oz
Dimensions 9 × 16 × 1 in
Include Parts

YES, NO

Solder Parts

YES, NO

RF Modulator Bypass

To use the RF modulator bypass circuit you’ll need these additional components.

T1, T2 – BC547
R14, R15, R18 – 150 ohm 1/2 watt
R8 – 1K
R9 – 3.3K
R10 – 5.6K
R11 – 68 ohm
R12 – 220 ohm
R13 – 75 ohm
R20 – 470 ohm
L6 – 10uH
CR3 – 1N4148
C35 – 330pF
C55 – 68pF

Optional:

You can choose to get these 2 trimmer resistors but they are not necessary. When not using the trimmer resistors you can close solder bridges at SJ1 and SJ2.

RV1 – 1K Multi-turn Trimmer
RV2 – 220 ohm Multi-turn Trimmer

EEPROMs

Downloads:

How to concatenate ROM images:

In Windows you would simply use the following command:

copy /b romfile1.bin+romfile2.bin romfilecombined.bin

ROM Jumper Settings:

2021.07.14-MELIUS-ROM-JUMPER-SETTINGS

Memory

For memory you have 2 options.

  1. Legacy 41464 DRAM. The same memory that is used in the 250469 boards or..
  2. SRAM

Legacy 41464 DRAM:

U43 – 41464-10 DRAM 256Kbit 64Kx4

U44 – 41464-10 DRAM 256Kbit 64Kx4

C25 – 0.1uF

C28 – 0.1uF

 

SRAM:

U40 – Alliance AS6C1008-55PIN 1Mbit 55ns SRAM

U41 – SN74HCT573N Tri-State Octal D-Type Latch

U42 – SN74HC32 Quad 2 Input OR Gate

C26 – 0.1uF

C27 – 0.1uF

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