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Thread: AT compact clone - 384k + RTC card just caught fire - what do?

  1. #1
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    Default PC compact clone - 384k + RTC card just caught fire - what do?

    Today ended with a bang...

    I have a V20-based PC clone (V20+8087/640KB/20mb MFM HDD/Hercules/720k+360k). This beautiful multifunction-essential card just burned up and filled the whole place with smoke I'm pretty sure the battery leakage did it in, though it didn't look too bad, definitely a word of caution to those playing with battery-leak damaged cards. Apparently it can cause a fire...
    (update: whoops, originally thought AT)
    (update: Okay, so it's not an XT either Closer to IBM PC by its DIP switch settings. More photos in later reply.)

    IMG_20181012_193844389.jpgIMG_20181012_193847795.jpg

    RIP.

    Now even without the card, I'm getting a 4055 201 memory error at startup. Maybe there's a DIP switch on the board (inaccessible without meticulous disassembly) set to expect this card installed...

    What can I do to replace the card? I see there's a memory card from Lo-Tek that adds 1MB, but ... that doesn't really help with the now missing RTC.

    Tried looking on eBay but all I found is some odd card that even the owner doesn't seem to quite know about: https://ebay.us/fPeRs8

    I imagine the RAM is still ... well, maybe still good. 384KB in 6 banks * 9 chips with only 3 chips charred by the blaze. Pulled chips off the M/B and started getting 3xxx series then 2xxx series errors, reinstalled and it went to 4055 again - so all the onboard RAM seems (?) OK (?) given the behavior...

    I guess the question is, anyone know where I can get a replacement RAM/RTC card?
    Last edited by FalconFour; October 13th, 2018 at 08:00 PM.

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    Quote Originally Posted by FalconFour View Post

    Tried looking on eBay but all I found is some odd card that even the owner doesn't seem to quite know about: https://ebay.us/fPeRs8
    That is some sort of video capture card, and looking upi the patent it appears to be for the S-100 type systems. I am guessing the manual is not for that card at all.


    Quote Originally Posted by FalconFour View Post
    I have a V20-based AT clone (V20+8087/640KB/20mb MFM HDD/Hercules/720k+360k).
    Are you sure about that? The V-20 is a drop in replacement for the 8088 CPU, which is an XT class machine. The rest of your stats seem to also imply an XT class clone (so a clone of the IBM 5150 or 5160).

    Quote Originally Posted by FalconFour View Post
    I guess the question is, anyone know where I can get a replacement RAM/RTC card?
    Look for something like the AST Six Pack, although the Lo-tech card might be quicker and easier to get. RTC wise, there were some other options out there too, though I can't think of any off the top of my head, but do you really need an RTC?

    IBM 5160 - 360k, 1.44Mb Floppies, NEC V20, 8087-3, 45MB MFM Hard Drive, Vega 7 Graphics, IBM 5154 Monitor running MS-DOS 5.00
    IBM PCJr Model 48360 640kb RAM, NEC V20,, jrIDE Side Cart, 360kb Floppy drives running MS-DOS 5.00
    Evergreen Am5x86-133 64Mb Ram, 8gb HDD, SB16 in a modified ATX case running IBM PC-DOS 7.10

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    Hmm, don't I need an RTC? I thought it was one of those things that was just straight-up expected of hardware after it became a standard and integrated into every later system. I'd been having to set the clock every time it started up, since it had no battery (after removal of the one that later proved to be its demise)... so would it just still function that way without an RTC?

    Yeah, it's a V20 upgraded system (also the 8087), probably started life as an 8088. One-owner PC, and he did CAD stuff on it and needed the number-cruncher chip.

    Probably right about the XT thing. I assumed AT since it had a layout that would directly accomodate my big 80386DX board and seemed to be a later board than that 5150 I last played with, but yeah, I can't quite make out the defining features of pre-386 systems 386 was my earliest experience with PCs.

    Good sleuthing on that card! Dang fair guess the manual and card are unrelated, too. I know a 384k RAM card when I see it, that's why I was suspicious and didn't Buy It Now right away, haha.

    I'll check out that AST card next...

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    Iíd also be thinking that there is a jumper setting on the motherboard that needs to be changed to stop the Bios looking for the extra memory at startup. Iím guessing your motherboard has 256K on board, with the 384K from the torched card making up the 640K?

    From what I have read, most (if not all) XTs didnít come with RTCs, so they were one of the most popular Ďadd-oní boards at the time. No problem not having one if you donít mind setting the time and date at each boot-up.

    Iíve ordered a ISA prototype board from Tex-Elec with the sole purpose of adding a RTC to my Commodore PC-10. Itís only a handful of components, so Iíll let you know how I get on if you want to do the same.

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    Quote Originally Posted by FalconFour View Post
    Now even without the card, I'm getting a 4055 201 memory error at startup. Maybe there's a DIP switch on the board (inaccessible without meticulous disassembly) set to expect this card installed...
    Your machine is behaving more like a PC clone, rather than an XT clone:
    - 'XXXX 201' formatted RAM error, like the IBM PC, rather than the IBM XT's format of 'XXXXX XX 201';
    - 'Removal of a expansion card equipped with conventional memory results in a RAM error' does not happen in an IBM XT, but does in an IBM PC.

    The '40' in '4055 201' indicates an error at address 256K, suggesting that you have 256K on the motherboard.

    Quote Originally Posted by FalconFour View Post
    Maybe there's a DIP switch on the board (inaccessible without meticulous disassembly) set to expect this card installed...
    That sounds right, like switch bank SW2 in an IBM PC, which is set to the total amount of conventional memory in the machine.

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    Hmm, maybe some Frankenstein hybrid?

    Here's a few photos (some from before the burn, sadly). It has 8 slots, figured that was an XT thing at minimum, but maybe closer to a PC/5150 in architecture?

    IMG_20181013_175906283.jpg IMG_20181013_180212359.jpg IMG_20181008_161929695.jpg IMG_20181007_203004198.jpg IMG_20181008_190840311.jpg

    I ran the DIP switches through the reference at http://minuszerodegrees.net/5150/mis...h_settings.htm - and SW2 made perfect sense (it was configured exactly as the PC is), and SW1 also made sense for 640k configuration. So I adjusted SW1 to match 256k. Now I'll fire it up and see how it goes

    (One post closer to being out of newbie-member post-approval purgatory, hah )

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    OK, it now starts up and works great, though with only 256K RAM... no more Windows 3.0 for me for the foreseeable future, hah.

    Kinda heartbroken over the loss of that expansion board, though. It's got 54 x 64kbit RAM chips on it, heavy as hell... all probably working just fine.

    It bugs me to no end that there don't seem to be any open-source/freely-printable PCBs to make a new RTC+RAM card from. Maybe drilling somewhere near 1,000 PCB holes might be a tall order for a fab house, but folks like DirtyPCBs don't put a constraint on holes in boards Maybe doable/done? Any hope of reusing these RAM chips?

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    Quote Originally Posted by FalconFour View Post
    It bugs me to no end that there don't seem to be any open-source/freely-printable PCBs to make a new RTC+RAM card from.
    I'm no PCB expert, but an RTC doesn't look very complicated. Some of the pics on ebay are clear enough that you can almost see all of the traces: https://www.ebay.com/itm/Real-Time-C...d/173255192260

    I wonder if the people making these: https://www.lo-tech.co.uk/product/1mb-ram-board-pcb/ would see enough demand to include RTC as well. I assume there are SMD RTC components that could be used to make the stuff fit better with their current designs.

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    You may look into the 1MB ISA RAM card from lo-tech, it can fill conventional memory and UMBs so essentially replace the memory you lost. It doesn't have a RTC though.
    https://www.lo-tech.co.uk/wiki/1MB-RAM-Board
    There is a seller on ebay who has both bare PCBs and assembled boards (though the latter are quite expensive) https://www.ebay.com/str/texelec
    Lo-tech no longer sells the PCBs directly. 1MB PCB: https://www.ebay.com/itm/PCB-Only-Lo...0AAOSwI59aOdLe
    I/O, I/O,
    It's off to disk I go,
    With a bit and a byte
    And a read and a write,
    I/O, I/O

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