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Thread: Kaypro 4/84 ROM chips orientation question

  1. #1
    Join Date
    Feb 2015
    Location
    Cleveland, OH, USA
    Posts
    859

    Default Kaypro 4/84 ROM chips orientation question

    After a long delay I began reassembling a Kaypro 48/4. I had begun work last year but put it aside with the board stripped and cleaned.

    Today I reinserted the chips on the motherboard, using the technical manual as a guide. Since some of the chips didn't exactly match the manual's designations I had to look up a few on the Internet to be sure I was putting the right chip in the right place. To make doubly sure I referred to the picture I took at the beginning of the project. That pic is attached below.

    I noticed right away that the character ROM (U9) and "monitor ROM" (BIOS, U34) in the picture were both indeed shorter than their socket but that I had inserted them flush left and before disassembly they were inserted flush right. I referred to another 4/84 board and it too has the ROMs flush right, so I assume this is correct, but my question is: Can anyone confirm this?

    Thanks for your replies.

    -CH-

    BoardBeforeDisassembly.jpg

  2. #2

    Default

    Mine has the 81-478 which is 28-pin, but the CG ROM is registered at the "bottom" of the socket (as viewed with pin-1 "up"). That was typical for the 24/28 pin EPROM compatibility.

  3. #3
    Join Date
    Apr 2018
    Location
    Los Angeles, CA
    Posts
    390

    Default

    On my 2/84 board.. both flush to the right. There is a photo attached to my kaypro 2/84 thread in this forum, but apparently no way to add it to this post while I'm replying on mobile (and too lazy to go to PC), but you can check that one to compare since the boards are similar.
    -- Brian

    Working Retro PC's: Apple IIe/II+, Atari 800, Atari 520STFM, Commodore 64, Commodore Amiga 3000, Commodore SX-64, IBM PS/1 2121-B82, Kaypro II, Tandy 1000 SX, TI-99/4A, TRS-80 Model 4 GA

  4. #4
    Join Date
    Feb 2015
    Location
    Cleveland, OH, USA
    Posts
    859

    Default

    Thanks for your replies. I moved the ROMs and reinstalled the board; the machine presents the familiar "Insert disk in drive A" and booted to Kaypro 63k CP/M V. 2.2G. Responded to DIR command, so the keyboard looks okay at first glance. At least it is communicating; haven't checked all the keys yet.

    Video is stable and brightness variable from blank to bloom. Focus is a little off in the corners; maybe that can be tweaked.

    I noticed the floppy drive harness has connectors for grounding the drives but I didn't see any connection point on the drives themselves. I tried to find a way to jury-rig a spade connector but in the end decided it might come loose and short something so I let it go. I assume grounding of the drives to the chassis occurs through the mounting screws.

    While I had it apart I made a few modifications: I removed the 115 VAC fan and substituted an 80mm 12 VDC. It is both lighter and quieter. I also ditched the filter, which was plastic foam and had deteriorated, figuring that I was blowing air out of the case and didn't need to filter it... I stole power (0.15 A) from the floppy power harness.

    I also replaced the on-board battery with a tray and a 1/2 AA rechargeable. I think the original was 3 VDC; this is nominally 3.6 but it measured 3.1 when I inserted it this morning. We'll see if it charges after use. (I think that's a charging circuit, isn't it?)

    Sometime soon I will swap out the 81-292 ROM for a KayPlus, Advent or MicroCornucopia ROM but there's other work to be done before that.

    Two more questions: What was the intent of including J9 on the board? And why does the harness include a Molex connector with only two wires (black and white) and providing 5 VDC? For what?

    Thanks again for all your help.

    -CH-

  5. #5

    Default

    J9 is the harddisk connector, although it could also be considered a generic I/O expansion interface. I'm not sure which power harness connector you're talking about, but it's possible that was for the WD1002 (HDD controller), which only used 5V.

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