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Thread: Fix amiga 1200 yellow screen

  1. #11
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    A1200 circuit diagrams can be found here:-

    https://www.amigawiki.org/doku.php?i...ice:schematics

    Are any of the RAM chips getting warm after a while?
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    Amibayer! Bryce's Avatar
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    Quote Originally Posted by soviet9922 View Post
    Quote Originally Posted by Merlin View Post
    Green screen is a Chip RAM fault, I suggest you check all RAM Chip connections. Why was the board covered in flux, was it repaired previously?
    The guy that was the original owner of the board tried to "reflow" the board using a hot air station.
    He obviously covered it in 1 liter of yellow stick flux and heated the chips up, of course he don't fixed the issue.
    Now he told me that he was getting green screen before the reflow operation so think the yellow screen was caused by all the flux.

    I checked the pins on the rams and most ics using the microscope and i don't see any bad solder joints at least on the ram and main ics.
    Flux doesn't conduct, so it's unlikely that the flux was the issue. Possibly reseating the socketed IC's when you cleaned the board could have caused the change from yellow to green. As well as that, if he didn't know what he was doing with the hot air station, he may have fried some chip from the heat.

    Bryce.

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    soviet9922's Avatar
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    Quote Originally Posted by Bryce View Post
    Quote Originally Posted by soviet9922 View Post
    Quote Originally Posted by Merlin View Post
    Green screen is a Chip RAM fault, I suggest you check all RAM Chip connections. Why was the board covered in flux, was it repaired previously?
    The guy that was the original owner of the board tried to "reflow" the board using a hot air station.
    He obviously covered it in 1 liter of yellow stick flux and heated the chips up, of course he don't fixed the issue.
    Now he told me that he was getting green screen before the reflow operation so think the yellow screen was caused by all the flux.

    I checked the pins on the rams and most ics using the microscope and i don't see any bad solder joints at least on the ram and main ics.
    Flux doesn't conduct, so it's unlikely that the flux was the issue. Possibly reseating the socketed IC's when you cleaned the board could have caused the change from yellow to green. As well as that, if he didn't know what he was doing with the hot air station, he may have fried some chip from the heat.

    Bryce.

    Now about the flux, i have in the past tested home build boards and computers and have glitches and things happening until i cleaned the flux, flux is not conductive but why it can make this kind of problems ?.
    For example in this video the 8 bit guy have the very same issue until he cleans the flux from the board:
    https://youtu.be/KAivGLHJzJM?t=1019

  4. #14
    Amibayer! Bryce's Avatar
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    It all depends on the type of flux you used. Rosin based fluxes are non-conductive unless you heated it so much that it turned black at which point it is full of carbon and will create a resistor. The other possibility is that there were also microroplets of solder in the flux and these were creating little capacitors all over the board. Generally, it's always a good idea to clean a PCB after building it anyway.

    Bryce.

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