Commodore 64 – 250407 – MELIUS Rev 1.2 (Second Batch)

$25.00

Here’s your chance to own a brand new Commodore 64 – MELIUS Rev 1.2 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.

Revision 1.2 continues to add new features

  • Modified footprints for the Axial Electrolytic capacitors to support radial capacitors.
  • Modified Clock Oscillation circuit to minimize the amount of components in that space which resulted in 2 additional modifications:
    • Support was added for a 2nd VIC chip as well as a second crystal which makes it possible to have both a 6567 and 6569 VIC chip installed and then use jumpers to easily switch between NTSC and PAL
    • Since the 8701 clock oscillator is no longer manufactured a supporting circuit was added that requires surface mount components to support the 525 user configurable clock circuit instead. So you’ll have a choice of using those components or simply using an 8701 or 8701 replacement.
    • Created a place for the capacitor that needed to be put in place with R38, this is just above R38 and is labeled C43.

Don’t miss your opportunity to own 1 of only 5 in existence of an official DIY Chris C64 250407 MELIUS Rev 1.2 first ever in existence. Who knows, I may become famous one day hahaha..

Out of stock

Here’s your chance to own a brand new Commodore 64 – MELIUS Rev 1.2 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.

NEW IN THIS REVISION!!!

Revision 1.2 builds upon these modifications with the following:

  • Modified footprints for the Axial Electrolytic capacitors to support radial capacitors.
  • Modified Clock Oscillation circuit to minimize the amount of components in that space which resulted in 2 additional modifications:
    • Support was added for a 2nd VIC chip as well as a second crystal which makes it possible to have both a 6567 and 6569 VIC chip installed and then use jumpers to easily switch between NTSC and PAL
    • Since the 8701 clock oscillator is no longer manufactured a supporting circuit was added that requires surface mount components to support the 525 user configurable clock circuit instead. So you’ll have a choice of using those components or simply using an 8701 or 8701 replacement.
    • Created a place for the capacitor that needed to be put in place with R38, this is just above R38 and is labeled C43.

This is the second batch and with the exception of 1 minor issue (which can be worked around) this board tests working 100%.

  • The only issue.. The surface mount section in the video area to mount the components that would make up the TOLB (replacement for MOS8701) has a disconnected pin. To fix just bridge PIN 13 to PIN 14 when soldering in U47 which is the 525 configurable clock

The order for the production run of Rev 1.2 is already in and has the PIN 13 issue fixed.

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 1.2 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

Missing Silk Screen

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