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Thread: Commodore Plus/4 black screen

  1. #1

    Default Commodore Plus/4 black screen

    Dear All,
    I've got a very beautiful Commodore Plus/4 that turns on but... the screen on the TV is pitch black. No other signs of life.
    I have only checked the computer with a TV but I am looking for a DIN to SCART cable to check the computer with a monitor...
    Supposing it is not a matter of RF modulator, my hope is that such a problem could be related only on a single killer/killed chip (I have checked the easy components and they work as supposed): the CPU, the TED...
    Do somebody have a possible culprit list? Hoping not all chips bring to a black screen...
    I also see that more or less all of them are socketed and this is good!

  2. #2
    Join Date
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    Check the output and input voltages in the regulators on the motherboard maybe your psu or one of the regulators is bad.
    Also if the kernal rom can go bad burn another 27128 eprom and replace it, theres a diag rom for it.
    http://inchocks.co.uk/commodore/Diag...al/Diag264.htm
    IF the PLA is bad this also can get you a black screen if you have another try swaping it.

  3. #3

    Default

    Quote Originally Posted by flaviosr View Post
    Dear All,
    I've got a very beautiful Commodore Plus/4 that turns on but... the screen on the TV is pitch black. No other signs of life.
    I have only checked the computer with a TV but I am looking for a DIN to SCART cable to check the computer with a monitor...
    Supposing it is not a matter of RF modulator, my hope is that such a problem could be related only on a single killer/killed chip (I have checked the easy components and they work as supposed): the CPU, the TED...
    Do somebody have a possible culprit list? Hoping not all chips bring to a black screen...
    I also see that more or less all of them are socketed and this is good!
    In my limited (< 10 cases) with the 264 series, the most common failure is the CPU.

    Frank IZ8DWF

  4. #4

    Default

    I finally got a C16 and five seconds after turning it on to test it today the screen turned to strange flashing colors. I was impressed by the clarity of the 40 column display until it suddenly stopped working

    Only posing here to commiserate. The quality of the TED line of computers is apparently terrible.

    My guess is that TED or some color ram somewhere gave out. I have a working Plus/4 so I am not even going to try troubleshooting right now. I am so mad at it it is banished to the closet until I have time to work on it.

  5. #5

    Default

    Just solved the issue... I have another working Plus/4 and I started switching the socketed chips!!! The PLA is gone... I have a not working C16 and I hope the PLA is alive!!!
    I let you know...

  6. #6

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    Quote Originally Posted by flaviosr View Post
    Just solved the issue... I have another working Plus/4 and I started switching the socketed chips!!! The PLA is gone... I have a not working C16 and I hope the PLA is alive!!!
    I let you know...
    I cried "VICTORY" too early. I was right about the chip but the Plus/4 does not start anyway!
    I have "finally" unmounted the motherboard and... I found what it seems to me a disaster on the below side!
    PIC_20181012_201524.jpg
    PIC_20181012_201556.jpg
    PIC_20181012_201620.jpg
    PIC_20181012_201637.jpg
    Or at least it seems a disaster to me.
    I see strange brown areas, big welding point (very big), wrinkles...

    Can somebody make a judgement/give some suggestions...?

  7. #7
    Join Date
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    The brown is flux residue. That's fine.
    Likewise the wrinkles are just abnormally thick solder that is under the green masking from when the board was originally built. It doesn't look pretty but that's fine as well.
    = Excellent space heater

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