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Thread: DEC Rainbow modern display options

  1. #1
    Join Date
    Jun 2018
    Location
    Troon, Scotland, UK
    Posts
    3

    Default DEC Rainbow modern display options

    Hi,

    I have a DEC Rainbow 100B which has the colour graphics option fitted. When I received the machine late last year, it had a faulty VR201 with it which was unfortunately beyond repair. As a replacement I made up a cable to use the composite input on a TV instead. While this works, it isn't perfect as it is only monochrome and none of the many TVs I have tried it on display the full picture as part of the left hand side of the image is always cut off. I am now looking for a way to hook the machine up preferably to a VGA monitor or TV with VGA input to support colour (and hopefully get a full image) as I can't find any replacement original monitors and also lack the space to keep one around.

    Does anyone have any experience in getting a Rainbow to output to a modern display in colour?

    Thanks!

  2. #2
    Join Date
    Mar 2008
    Location
    Westchester County, NY
    Posts
    1,254

    Default

    I'm sorry to hear that you think your VR241 is beyond repair. I'm not sure what that means since I repair everything. I might only call a bad CRT "beyond repair".

    Yes, I have connected my Rainbow (and the VT240, which in color would use the same VR241 monitor) to other monitors. The Rainbow output is RGB with synch on green. I am away from home at the moment or else I would look up the number of scan lines, etc. in my notes. You can look that up yourself on the internet however. There should be old threads right here on the forum with that data.

    I have a Pioneer plasma (yes, I got it broken and fixed it) that I use : http://www.vcfed.org/forum/album.php...chmentid=14600 . I like having a giant display for my VT240.

    Also, I have used an arcade game board to go to VGA for display on a VGA monitor (See here and the other photos in this album: http://www.vcfed.org/forum/album.php...chmentid=16642) I did have to use an LM1881 synch stripper to separate the synch from the RGB to satisfy this board. The heart is a board called GBS 8200 which is still on Ebay for $20USD.

    This should give you plenty to chew on. Or perhaps you can fix your VR241 ...

    Lou

  3. #3

    Default

    The R* has a weird resolution, something like 800 x 240 lines. If the picture is coherent and a part of the screen is truncated, I would think that could be remedied via one of the trimpot controls. To display that video on a vga though you would need some sort of scan doubler. If I'm right about the 240 vertical lines, that's exactly half of standard vga. Scan doublers for Amigas are common and run around 100$. Not saying they'd work right out of the box though.

  4. #4

    Default

    A̶r̶e̶ ̶y̶o̶u̶ ̶s̶u̶r̶e̶ ̶i̶t̶'̶s̶ ̶R̶G̶s̶B̶?̶ ̶I̶'̶v̶e̶ ̶g̶o̶t̶ ̶t̶h̶e̶ ̶t̶e̶c̶h̶n̶i̶c̶a̶l̶ ̶m̶a̶n̶u̶a̶l̶ ̶f̶o̶r̶ ̶t̶h̶e̶ ̶D̶E̶C̶ ̶R̶a̶i̶n̶b̶o̶w̶ ̶a̶n̶d̶ ̶t̶h̶e̶ ̶v̶i̶d̶e̶o̶ ̶o̶u̶t̶p̶u̶t̶ ̶i̶s̶ ̶d̶e̶s̶c̶r̶i̶b̶e̶d̶ ̶a̶s̶ ̶b̶e̶i̶n̶g̶ ̶a̶ ̶c̶o̶m̶p̶o̶s̶i̶t̶e̶ ̶s̶y̶n̶c̶ ̶s̶i̶g̶n̶a̶l̶ ̶a̶n̶d̶ ̶t̶h̶e̶ ̶v̶i̶d̶e̶o̶ ̶c̶o̶n̶n̶e̶c̶t̶o̶r̶ ̶o̶n̶ ̶t̶h̶e̶ ̶R̶a̶i̶n̶b̶o̶w̶ ̶d̶o̶e̶s̶n̶'̶t̶ ̶s̶p̶l̶i̶t̶ ̶i̶n̶t̶o̶ ̶R̶G̶B̶ ̶o̶n̶l̶y̶ ̶c̶o̶m̶p̶o̶s̶i̶t̶e̶.̶

    Never mind me, didn't see you had the color option installed!

  5. #5

    Default

    Perhaps the original poster does not have time nor skills to engineer a solution....The display you want is a VR-241a with the associated cable. Maybe you'll get lucky and find one of these in your area.
    b
    @ BillDeg:
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  6. #6
    Join Date
    Aug 2006
    Location
    Chicagoland, Illinois, USA
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    Default

    With the color output being analog RGB with sync-on-green, it should be very possible to use an external scan converter to connect up a VGA display. The Gonbes GBS 8200 is a cheap, if subpar, solution; the open-source scan converter (OSSC) might also work.
    Offering a bounty for:
    - The software "Overhead Express" (doesn't have to be original, can be a copy)
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Documentation and original disks for: Panasonic Sr. Partner, Zenith Z-160 series
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  7. #7

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    Why is the gonbes subpar?

  8. #8
    Join Date
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    Default

    It has slightly noisy analog output, the scaling is terrible (nearest-neighbor), and some combinations of model + resolution produce random white "speckles" because they are driving the RAM too hard (ie. RAM not fast enough). There is a fix for the latter issue; a google search can locate it.
    Offering a bounty for:
    - The software "Overhead Express" (doesn't have to be original, can be a copy)
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Documentation and original disks for: Panasonic Sr. Partner, Zenith Z-160 series
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  9. #9
    Join Date
    Mar 2008
    Location
    Westchester County, NY
    Posts
    1,254

    Default

    Judge for yourself. Here is the output of my GBS 8200 on a 1024x768 LCD monitor : http://www.vcfed.org/forum/album.php...chmentid=16638 . This is the setup screen from the VT240. Of course the picture on my real VR241 is better, but for what this board cost, I personally was satisfied.

    Lou

  10. #10
    Join Date
    Aug 2006
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    Chicagoland, Illinois, USA
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    Default

    "For what this board cost" is the operative phrase. If you need to get something up and running, the board is fine for that purpose. But it's not going to win any quality awards.
    Offering a bounty for:
    - The software "Overhead Express" (doesn't have to be original, can be a copy)
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Documentation and original disks for: Panasonic Sr. Partner, Zenith Z-160 series
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

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