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Custom build Amiga 500++

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  • Custom build Amiga 500++

    Hi Everybody!

    My name is Thomas, please allow me to introduce my latest work, it's story, history (and maybe future)...
    It all started out with my Atari ST basically kicking the bucket one day and myself thinking ... here, you collect them, care for them and then their gone.
    So, first (self) question was: how can you ensure the longest lifespan of a retro computer?
    (option to keep it on a shelf and not power it on excluded )

    I could produce only one answer: use new components wherever possible.
    That would mean new PCB, all new passives and logic IC's, use old chips only for non replaceable IC's.

    And so all started ... yet the new Amiga had to fulfill a few pre-requirements:
    1. it should run the original 8MHz processor - I see no point for CPU accelerator (personal opinion)
    2. it should have switchable kickrom (at least 1.3 / 3.1)
    3. it should have extra (FastRAM) memory
    4. it should have an IDE HDD controller
    5. it should be able to handle both Floppies and disk images (Gotek), not necessarily in the same time
    6. it should support a PC keyboard
    7. it should support modern displays
    8. Not planned/installed but since it is a A500+ it can hold up to 2MB ChipRAM.

    Collected all the required chips via ebay, a new PCB from Bob on Tindies, passives from Mouser/TME and many many more.

    This was the result:

    Click image for larger version

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    Details about the building process and what's inside, next post...

    - - - Updated - - -

    Major issue was the case. I snooped endless times around the Checkmate A1500 case but nonmatter how strong the attraction was, could newer get over the price (please do not get me wrong, I am not implying it's overpriced, it was just out of budget for me).
    So, what to do? Well, a PC case has to do and here, I had a lot of constrains.
    Case needs to look great (or at least OK), quality decent, needs to be small, should have a 3.5" or 5.25" drive bay (quite a challenge these days), not be too pricey and (did I mention?) look great ?
    As a matter of fact and one month later, the victim has been identified: Aerocool's Playa Slim, around 45EUR, unfortunately black (try to find a white case today) but amazingly with a front panel that loosely resembles the Amiga 1000 original front panel.

    The Amiga motherboard fits and with a little bit of help sits stable within the case. The mouse, joystick and audio out ports match the exact opening for the PC power supply (not used). The other ports, I get to them later.
    Click image for larger version

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    Having constrains caused by the PC case some connectors were skipped. Namely the serial and parallel port connector. All the components have been soldered except the connectors. Easiest option would be to solder some wires and mount connector in one free extension slot space. For me it was (is) no priority therefore not done.
    Another unpopulated area is the analog video part. Having an Indivision ECS V2 installed which provides VGA video output directly from the Denise (which it also replaces), there is no need for the analog circuitry.

    For RAM extension and IDE controller the best (technical and financial) option was the M508 interface designed by Matze and available for around 100EUR.
    Hard drive, initially was a Compact Flash card and the computer was totally silent when powered on (since no PSU cooling fan needed). Although I do not like noisy computers nor do I love totally silent ones. Therefore now there is a 2.5" hard drive installed (capacity is 40GB but I formatted only 2GB for safety) and we have a very faint zumming while powered on.

    PC keyboard interface is self made, based on info found on EAB board, posted by Solo761. Simple schematic with PIC 16F628 that will convert amiga keyboard interface to a standard PC AT (or PS/2) keyboard interface.

    Floppy: I wanted to have possibility to use real floppies as well as ADF images, not necessarily the same time. After some googling and one day of trial&fail found the right signals that need to be switched so that both drives (FDD and Gotek) configured as Drive 0 can stay permanently connected. Depending on switch setting one of them is active.

    Power supply: needed something that can provide the required voltages namely +5 +12 -12 and amperage. Solution, simple, MeanWell RT65B used by many Amigans to replace the old PSU.

    Now motherboard is prepared, power input connector replaced and adapted to accept wires from internal power supply, all passives soldered, components placed in sockets. All worked on first power on. Quickly loaded Battle Squadron for test.

    the motherboard fit in, almost on the limit. Some new holes had to be drilled for the PCB standoff feet. ATX backplate is custom made, aluminum sheet covered with black foil.

    Since it had no other use, I connected the front power button as reset switch.
    Also activity signal from IDE controller is "mixed" together with FDD activity LED and connected to front panel IDE LED
    Although it was not my goal to have a colored LED bar on the frontpanel, it came standard with the case - totally useless but doesn't do any harm either. Fixed color or color cycling can be selected by a small button on front panel.
    Click image for larger version

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    The floppy drive installed with the use of a 5.25" -> 3.5" adapter fitted quite nicely in the 5.25" CDROM bay. Without any other available drive bays, the Gotek had to go inside the case. Anyway, even with available bays I would have still put the Gotek inside ... I just don't like how it looks in a 3.5" slot.
    With the Gotek drive inside we need to bring out: USB port for Memorystick, some display, buttons or rotary encoder. Cutting case for LCD display was out of question so I wired the display signals to one of the USB ports on case.

    The other USB port is for the stick. The rotary selector is mounted on back of the case.
    The internal floppy drive is actually a HD 1.44MB PC drive that has been modded to function as an Amiga DD drive.

    All selectable options have been wired to switches on back panel.

    Generally I am satisfied with the result, all project goals have been met, system works perfectly.

    But (there is a "but") ... I always wanted an A2000 and although this project can be considered a success (from my point of view) I still can not escape the dream of having an Amiga 2000 ... therefore this project goes up for sale ... will post it here in the "hardware for sale" section anytime soon ...
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