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NEC APC III

Discussion in 'Retro & Arcade' started by sean0118, May 2, 2020.

  1. sean0118

    sean0118 Member

    Joined:
    Jul 24, 2012
    Messages:
    192
    Location:
    Sydney
    I have a bit of time at the moment so I thought I'd get stuck into fixing my two NEC APC IIIs, I've had them for over two years now so time to take a look.

    I don't have the keyboard or monitor, both of which I'm fairly sure are a proprietary NEC design and not PC compatible. But the main issue at the moment is both of them don't turn on, no LED or fan, nothing at all.

    I took this first one apart, it seems the power supply is not supplying any voltages. It doesn't have a standby or enable line so it should be supplying all voltages as soon as it's turned on. I've done a little bit of investigating, the rectified mains is there, but the transistor on the primary side of the transformer is not being switched. That might make it a difficult fix because the primary side controller is some strange zip package labeled "YEC YD-010 4Y2", pretty sure it'll be really hard to find a datasheet for. I've tested most of the components around it and replaced the smaller electrolytic capacitors, but no luck yet.


    Anyway, I took a lot of photos so I could put it back together, it hasn't been cleaned so it's still pretty crusty, but here they are:

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    Pretty sure this is the HDD controller card:

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    NEC FYD051 / TEAC FD-55F-03-U floppy drive:

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    NEC D5126 HDD:

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    I found a bonus floppy disk stuck in the space between the floppy drive and HDD:

    :lol:

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    Memory card:

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    Sound card:

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    RS-232 Port Controller:

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    RAM expansion card (made in Australia :shock:):

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    YEC PU506 power supply:

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    I'll post an update when I get the power supply fixed. Then the next problem will be finding a suitable keyboard and monitor. Hopefully at least one person in the world collects these and the repair is worthwhile. :lol:


    edit: actually looking into it a bit more it seems the B/W display port can be hooked up to a generic NTSC tv / monitor. I've got one so I should be able to use that for testing eventually.

    edit2: EPROM BIOS binary files attached below
     

    Attached Files:

    Last edited: Jul 11, 2020 at 6:25 PM
  2. Pierre32

    Pierre32 Member

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    Oct 13, 2019
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    445
    Location:
    Sydney
    Beautiful kit, and this project is definitely set to hard mode.
     
    Vanne likes this.
  3. Vanne

    Vanne Member

    Joined:
    Apr 20, 2003
    Messages:
    1,445
    Amazing build, brings a tear to my eye when i see "Made in Australia!" soo cool. sadly not to be seen again id say.
    Cant wait to see where youd start. subbed.

    Where was that floppy hiding? in the drive, or underneath it? on purpose for the next techie thats gonna fix/tinker?
     
    okclock123 likes this.
  4. Phido

    Phido Member

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    The old NEC's are very nice odd machines.

    I had an original APC machine with 2 x 8 inch drives.. Which my brother took out to a farm and shot.. Sad about that one.
     
    darkmenace likes this.
  5. macplus

    macplus Member

    Joined:
    Jan 20, 2009
    Messages:
    114
    Used to see a heap of these things at Uni. We had the twin disk versions.

    I remember the colour display was quite nice.

    Looks like a bit of a proprietary nightmare though. Good luck!
     
  6. phorgetmenot

    phorgetmenot Member

    Joined:
    May 17, 2006
    Messages:
    16
    These things were fully IBM compatible and therefore everything worked under DOS if you had the Software Library Expander card (see https://www.old-computers.com/museum/computer.asp?c=996), so if you have one of those it can boot DOS and will run everything from that era. I don't remember the keyboard seeming proprietary, basically was similar to the IBM model-M. It had CGA graphics. Who else remembers the huge choice of either Black, Red, Green, Yellow _XOR_ Black, White, Pink, Blue (which tended to look way better). A few games (like Alley Cat) even used both (although not at the same time).
     
    adz likes this.
  7. OP
    OP
    sean0118

    sean0118 Member

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    Location:
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    Okay, time for an update. ;)


    Unfortunately I accidentally blew up the power supply while troubleshooting it. So I had to replace the main switching transistor and a resistor, while I was doing that I also replaced all the capacitors with good quality Japanese ones. Which fixed it,the power supply seems to work really well now.

    It now sounds like its booting up, LEDs come on and gives a few beeps because there's no keyboard or monitor attached.


    Yeah underneath it, couldn't get it out without removing the drive. There is a thin gap between the drive and front bezel, I think maybe someone shoved it in through there?


    The second one I have is the twin floppy disk version. I'll post some photos of that soon too.

    That would be really good if the keyboard isn't propriety and if it uses CGA graphics. I thought it used a 400 line monitor, but that may have been an earlier NEC model, I can't find the webpage now. I'm having a lot of trouble finding information about it.

    I did actually plug my CGA monitor into it, it resized the background of the display, but didn't display any text. But it's probably the CGA monitor which is at fault, it's one I repaired but couldn't get it to work with a CGA card I had. I should have another go at repairing it.

    For the moment I might try to use the NTSC (B/W) output. I've got an old Ferguson CRT which I think might work, but it has a different din connector on it, I've attached a photo of its label which shows the pinout.

    Is connecting just the Composite video and earth enough to get an image?

    Looking at the NTSC din connector pinout on this website (which I hope is the same as the NEC) I don't think the others are necessary, except maybe Composite Luminance?
    http://www.hardwarebook.info/Atari_8-bit_Monitor
     

    Attached Files:

    Last edited: Jun 6, 2020
    okclock123 and adz like this.
  8. elvis

    elvis Old school old fool

    Joined:
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    There was a time when this country did more interesting things than just dig up rocks.
     
  9. RichardE

    RichardE New Member

    Joined:
    Jun 22, 2020
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    Hey there just found one of these at a refuse site a few days ago.
    It looks surprisingly in good condition.
    It only has two 5.25 floppy drives.
    No expansion cards or hard drive.
    Thought I would touch base with you as I am trying to connect with like minded folk working on vintage equipment.
    Been finding alot of other computer equipment like 8088 XT IBM 5160s and amazingly a rare EXIDY Sorcerer Z80 computer with the S100 expansion bus.

    Ill leave it at that for now be interested know how you are going with your NEC systems these look like a pretty exclusive design.
    I dont have any 5.25 inch floppies so cannot test it atm.

    Cheers

    Richard
     
  10. Pierre32

    Pierre32 Member

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  11. RichardE

    RichardE New Member

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  12. RichardE

    RichardE New Member

    Joined:
    Jun 22, 2020
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    How are you going with your APC IIIs I have one here that I just picked up, no cards or hard drive just the two floppies.
    Do you know of any documentation.
    NEC seem to build it pretty custom.
    I think I will certainly clean it up and give it a test run.
    Looks well built and in pretty good condition but like yours mine needs a clean as well.

    Speak soon maybe.

    Cheers

    Richard
     
  13. OP
    OP
    sean0118

    sean0118 Member

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    Hey, sorry for the lack of updates, I've gone down a rabbit hole of trying to repair my CGA monitor so I can use it to test the APC IIIs. :lol:

    That was a good save, I don't think there would be many left in Australia. The IBMs and EXIDY Sorcerer Z80 were very nice finds as well.

    Sadly I haven't been able to find documentation either, doesn't seem like there's much information about them. I have backed up the BIOS binary files though, so I'll post that soon. I have a second APC III that I also want to backup the BIOs of in case it's different (it's a dual floppy version like yours).

    I'm more into the electronics repair side of things, so I'm not sure how useful I'll be. But let me know if your power supply doesn't turn on, I've already got a list of replacement capacitors for it.
     
  14. OP
    OP
    sean0118

    sean0118 Member

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    I'm not sure if it is true CGA graphics, I probed the output connector and got a V-freq of 56.4Hz and H-freq 24.8kHz.

    The H-freq in particular is quite a bit off:
    http://minuszerodegrees.net/mda_cga_ega/mda_cga_ega.htm

    I also probed the RGB signal pins but got nothing, I suspect the dip switches may need changing to use colour graphics.

    Or maybe it's just broken, the CGA/EGA CRT is also still in an unknown condition and may be broken. :Paranoid:
     
  15. RichardE

    RichardE New Member

    Joined:
    Jun 22, 2020
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    Here I need to rewrite that rubbish I wrote.

    I think the monitor for the APC III I have is sitting at the tip but I hestated to grab it I could not recall what state it was in.
    I will have a look tommorrow.
    Would you like me to send you this one Sean, I am not sure whether I will be best to keep it.
    I really would like the floppy drives though and maybe the processor, I understand if that makes it not worth while but maybe it is good for spares.

    Might be better for you than it sitting here for me as I probably wont have time to do anything with it.
    I will have another peak at it now.
    Speak soon.

    Richard
     
    Last edited: Jul 3, 2020
  16. OP
    OP
    sean0118

    sean0118 Member

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    Thanks, but I've already got my hands full with these two. I've got a whole stack of broken PCs and monitors to fix. :lol:

    Some of the NEC monitors are multisync so can work with lots of different types of graphics, quite sort after. If you don't want it I'm sure someone here on the forum would, the forum has a retro for sale section you could list it in. I think you should be able to unless there's limits because your account is new.

    Which state are you in?
     
  17. RichardE

    RichardE New Member

    Joined:
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    Western Australia
     
  18. OP
    OP
    sean0118

    sean0118 Member

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    Ok, I have got the second NEC APC III out, this ones a dual floppy version. Doesn't have any expansion cards, or a maths co-processor, the CPU is an NEC D8086D-2.

    The power supply on this one is the same model and date of manufacture (serial number is 8213, the other is 7813). It also wouldn't power on until I replaced all the electrolytic capacitors in it, must be a common issue.

    I copied the BIOS binary files from its EPROMs and added them to the top post. A few pins on one of the EPROMs were super corroded and it took a bit of work for it to be read correctly.

    I'm not getting any BIOS beeps on power up though, so I think the EPROMs or sockets might still have some issues. I probed the colour video connector too, getting 12V on pin 7 (Blue 0), that does not seem right at all, should be <5V as far as i know.

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    Last edited: Jul 11, 2020 at 7:04 PM

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