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Thread: New to me Rainbow 100A and VR201

  1. #1
    Join Date
    May 2011
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    Liverpool, England
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    Default New to me Rainbow 100A and VR201

    I have just purchased (won) a Rainbow 100A in box with VR201 screen, keyboard, software and a printer. I have yet to collect the item. I have never used or seen one of these as I was still in junior school when this one was purchased I've attached some pictures. I'm interested in cleaning the deteriated "glue" from the screen. I'd be interested in what methods and chemicals have been used to clean this with success?
    I have an RX50 in my PDP-11/53 so I'm aware of the reliability of this and will check the rainbow one over and use some old floppies first before inserting one of the Rainbow software floppies.s-l1600.jpgs-l1601.jpgs-l1602.jpgs-l1603.jpg

  2. #2

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    You may look after "CRT cataract". You will find videos and pictures.
    I did this using some Nylon cord, sawing the glass from the tube.
    Here is a picture of that procedure: http://www.retrobyte.de/images/img_3360-1000.jpg
    This took about one hour. The Nylon did not scratch the glass.

    Next time I will try this with a very stable and thin wire, maybe from a guitar or diamond litzwire for teathered flight.

    Greetings,
    Volker

  3. #3
    Join Date
    Jan 2010
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    Central VA
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    You have to disassemble the CRT and pull the safety glass off, then remove the PVA layer and clean up the face of the tube. There are plenty of videos on the process, search for "CRT cataracts" or "CRT mold."

  4. #4

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    I have successfully used butylacetate to dissolbe PVA in my VR201. Used a ink cartridge syringe to inject butylacetate inbetween the CRT and the front screen. After a week the PVA was dissolved and front glass came off without any problem.

    Butylacetate is smelling quite strongly but is not harmful. It is used in nail polish.

    I prefer this method rather than using a heat gun on the CRT.

  5. #5
    Join Date
    Jul 2014
    Location
    Rhode Island
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    When we disassembled the VR14 on the PDP-12 the front glass was only attached over about 10% of the surface so we could easily remove it.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  6. #6
    Join Date
    Feb 2012
    Location
    Northern Nevada
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    679

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    On a Rainbow 100, be sure to check the flex print cable from the power supply to the motherboard. If any of the parallel lines aren't conducting well, it can overload the others and cause the cable to melt.

    Also, it's possible to write Rainbow floppy images on PC with a high density 5.25 drive. I did this back in the 90's for my Rainbow 100A I had back then, no problems with read/write errors.
    Last edited by HoJoPo; August 23rd, 2019 at 08:50 AM.

  7. #7
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    Jan 2005
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    Principality of Xeon (NJ)
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    Default

    I was going to suggest a heat gun, but Mattis doesn't prefer it so maybe take his advice.

    The stuff used in nail polish over here is called acetone. Maybe it's the same stuff he mentioned. Also keep in mind that ammonia is a far better penetrant then acetone, at least when it comes to removing tiny bits of grit from recessed areas and crevaces. But it takes time. Soak an item for 24 - 48 hours, if it can take it. Notice I said better penetrant, not solvent, as there can be subtle differences. For this application a good solvent is probably recommended. We have something called PB Blaster over here, and CRC penetrant. Used by mechanics to free very rusty, stuck bolts. I wouldn't say the stuff works miracles, so not sure how much better it is then wd-40, Liquid Wrench, etc. PB will melt Styrofoam. Not sure if it'll dissolve glue to any extent. But it may be sufficient to break the bonds.

    I don't believe removing the CRT is necessary. Rather just the bezel would have to be detached.
    Last edited by tipc; August 23rd, 2019 at 10:17 AM.

  8. #8

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    Acetone can probably also be used. It will also dissolve PVA. But it has a much lover boiling temperature. Around 50 degrees centigrade while butylacetate is around 120. This means aceton will evaporate more quickly.

    My understanding is that aceton is used as nail polish remover. While the polish itself contain various ester as solvents.

    For dissolving PVA butylacetate or some other ester can be used. These alcoholic ester substances usually have a fruity odour in low concentration (actually there are those kind of substances in real fruit albeit in very low concentration)

  9. #9
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    Kamloops, BC, Canada
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    Quote Originally Posted by MattisLind View Post
    Acetone can probably also be used. It will also dissolve PVA. But it has a much lover boiling temperature. Around 50 degrees centigrade while butylacetate is around 120. This means acetone will evaporate more quickly.
    It's also very toxic and should never be used in unventilated areas.
    = Excellent space heater

  10. #10
    Join Date
    Jan 2005
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    Well I try to avoid breathing anything given I feel it immediately in my lungs. I don't spray cleaners at all anymore, except for glass cleaner on the windshield. I wasn't aware of specific toxicity of acetone. Clearly it's a chemical agent. But so is paint thinner, benzene, gasoline and kerosene (omg what a headache they give me). Always have ample ventilation. Even that Mr. Clean garbage makes my lungs burn.
    Last edited by tipc; August 23rd, 2019 at 02:05 PM.

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