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Thread: Northstar Advantage advice please.

  1. #1
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    Default Northstar Advantage advice please.

    So I'm the guy that bought the Northstar advantage on Ebay last week. I'm waiting for it to cross the pond to the UK so a few questions in the meantime if you don't mind....

    1. It has the screen 'problem' shown in the photo below - retrace lines visible so I"m hoping the seller just has the brightness control turned all the way up and its an easy fix - what else might it be - blanking circuit problem, scree voltage too high etc ?

    2. I belive from looking at the schematic that it's a relatively simple change to the transformer wiring to convert from 110V to 240 use - is that so ?

    3. Anyone have some hard sector boot media that I can acquire please ? Would love CP/M and the Advantage demo disk (pretty graphics demos)

    4. I do have a couple of working Northstar Horizons with hard sector media - are they boot compatible ?

    5. Were there ever any useful expansion bus cards produced for this system ?

    Thanks in advance.

    s-l1600.jpg

  2. #2

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    That screen looks like the brightness is too high. If you find you cannot turn it down low enough, look for a trimmer on the board. Probably labelled appropriately (brightness or contrast). If you need a hand bring it over.

    Cheers
    JonB

  3. #3
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    Default

    Thought so thanks Jon - could be worse and a sign that the flyback is on the way out but I'll take the optimistic view and assume the seller couldn't find the brightness knob on the back of the unit.

    I missed out on one of these in a UK auction recently so was quite please to get this one - I just hope it survives the journey.

  4. #4

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    Quote Originally Posted by zippysticks View Post
    ...could be worse and a sign that the flyback is on the way out...
    That's a definite possibility.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  5. #5

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    I don't think I've ever seen this from the flyback. Fiddle with the contrast and brightness. Usually it is a tired tube. You might also look at the input loading ( impedance matching ). Some expect there to be a 75 ohm load while others don't. This can sometimes make it harder for the display to pick out the horizontal and vertical blanking.
    The flyback failing usually causes blooming when turning the brightness up too much.
    Dwight

  6. #6

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    I have a N* but I don't think mine directly boots from the HD. I think it has to boot from disk first but I could be wrong, it has been a while since I played with it and it is in storage right now.
    Dwight

  7. #7
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    Quote Originally Posted by Dwight Elvey View Post
    I have a N* but I don't think mine directly boots from the HD. I think it has to boot from disk first but I could be wrong, it has been a while since I played with it and it is in storage right now.
    Dwight
    Sorry Dwight not sure I made myself clear when I mentioned looking for boot media - I'm looking for hard sector floppy boot disks.

    Thanks

  8. #8

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    Quote Originally Posted by zippysticks View Post
    Sorry Dwight not sure I made myself clear when I mentioned looking for boot media - I'm looking for hard sector floppy boot disks.

    Thanks
    Oops, I miss read it. I have a metal cover N* with a hard drive and another Horizon with wood cover. The availability of hard sectored disk is a hard one to find. Even 360K disk to punch holes in is tough. If you can get a bunch of 360K disk, you might be able to barrow a punch from someone at SEBHC ( Heathkit group ). I was involved with the first design but we targeted the cost too low and the ones we had made suffered from alignment issues that dulled the punch pin. A new batch were made using all metal design. I wasn't involved with it so don't know how they turned out. They were basically based on my original design. I doubt you'll get anyone to part with theirs but may find someone near that might let you barrow one.
    There is also a few people that are working on a USB floppy drive emulator to work with the more fussy N* controller.
    If you find some hard sectored disk, I can copy disk I have but I'm on the other side of the pond so it might be better to look more local.
    I do know that someone had a way to bootstrap a N* with disk images but don't recall who that was.
    Dwight

  9. #9

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    The 10 hard sector media is used for both the Horizon and the Advantage, but the Horizon disks will not boot an Advantage computer. However, you can use your Horizon computer to write bootable disks for your Advantage. See my page at http://deramp.com/downloads/north_st...tage/Software/

    I also have 10 hard sector media available if you need more disks.

    As far as the video display goes, it looks exactly like a monitor with the brightness and contrast knobs set too high. Shouldn’t be a problem.

    Mike

  10. #10

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    Quote Originally Posted by deramp5113 View Post
    As far as the video display goes, it looks exactly like a monitor with the brightness and contrast knobs set too high. Shouldn’t be a problem.

    Mike
    Agree completely. When the brightness and contrast controls are set correctly on the CRT, the video signal content (pixels on) shifts the beam into the illuminated state. A pixel zero is just a video voltage level that is black level, or less & extinguishes the beam. (Grey scales if any are in between black level and the beam at full intensity). During the vertical sync interval and vertical retrace time the video is at black level.

    If the CRT's brightness is set too high, the vertical retrace lines become visible, which is what you are seeing. During vertical retrace, the video signal level should be in the black level, and the retrace lines not visible with the brightness control set correctly.

    Some monitors & VDU's have internal retrace blanking (not all) where these somewhat annoying retrace lines are blanked by feeding the CRT with a pulse from the vertical scan oscillator that blanks(extinguishes) the beam, so if the user has the wrong setting of the brightness & contrast controls, the retrace lines are not visible. It was also a classic problem with early TV sets, before vertical retrace blanking became universal. Most manufacturers realized the punters didn't have the ability to correctly set the controls, so they introduced the vertical retrace blanking practically to every TV made after 1960. Oddly, the retrace lines were a useful guide on how to set the controls correctly, because when there, it created a guide how to correctly set the controls.
    Last edited by Hugo Holden; September 12th, 2019 at 10:55 PM.

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