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Thread: TRS-80 Model 1 and Model III pre-power on checklist

  1. #1

    Default TRS-80 Model 1 and Model III pre-power on checklist

    Some time back in listing to Trash-Talk podcast, the hosts had some tips on what to do if you find/buy an old TRS-80 prior to turning it on... as in too many people just turn them on and after all those years, the power supply takes down the system.

    Can someone run me through the recommended steps for both the Model 1 and Model 3? I have two of each and want to make sure all is good prior to energizing them.

    Thanks,

  2. #2
    Join Date
    Jun 2010
    Location
    Vancouver, BC, Canada
    Posts
    290

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    Ian Mavric has a good video on what to do with a Model III



    The two critical things are:

    1. Replace the RIFA caps in the power supply. Detailed guide: http://www.akhara.com/trs-80/psrepair/index.html

    2. Be very careful lifting the top off when opening up the machine so as not to break the CRT neck.

    I don't have any tips handy for the Model I, but it has neither of the Model III issues listed above.

  3. #3

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    Model I’s I will typically just power them up as there is little that will go bad. You could take an extra safety step and check the output voltages of the power supply you are using. Also, make sure you connect the video and power cables to the correct 5pin DIN connectors on the computer.

    For the Model III, as gp2000 mentioned, you really should at least check the Rifa filter caps on the PSU before powering up. If they are cracked, replace them now. If they look good, you’re probably ok to power up for awhile. But, replace them soon if you suspect they are originals. If they are marked X2, they are probably a more recent replacement.

    You could also check the PSU output voltages first to ensure they are correct. There have been cases where the PS will output too much voltage which will fry components, but this is very rare. To do this properly would require removing the PS and connecting to a testing rig to apply the correct loads on the PS circuits.

  4. #4
    Join Date
    Jun 2015
    Location
    Sioux Falls SD
    Posts
    177

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    I'd test a Model I stepwise if you have CPU/keyboard, expansion interface, and floppy drives. If the CPU won't boot to the Memory Size? or Mem Size question, then need to get that working before worrying about the rest.

    I'd then add the EI without floppy disks to see if it will boot while holding the [BREAK] key and recognize the memory in the EI.

    If all is good to this point, then try to boot a DOS disk.

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