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Thread: Tandy TRS-80 Model II Issues

  1. #1

    Default Tandy TRS-80 Model II Issues

    I am trying to restore a TRS-80 model II and have run into this problem.

    model II.jpg
    (sorry about the garbage picture, the phone camera wouldn't cooperate with the CRT refresh rate)


    When I power the system on, it displays this flickering screen with the message "Boot Error MF". I know that this means it has a memory fault, but I have tested all the RAM in the RAM card, and replaced the single faulty RAM chip with one from the other card. (it was a 32k system with another 32k card installed.)
    I realize that the boot error could be due to an addressing problem, but the flickering is what has got me stumped.

    So far I have done the following to the machine:
    -Recapped the PSU, CRT driver board, backplane, and all the logic cards.
    -Cleaned the card edges and connectors on all the cards and backplane
    -Tested all the RAM chips, and replaced faulty chip
    -Reseated all the DIP ICs
    -Removed all the cards apart from the CPU, Video card and Memory card, and still get the error. (the error is the same when the memory card is removed)
    -Rearranged the cards in the backplane

    Nothing so far has helped at all with the issue, so at this point I'm stumped.
    I'm new to TRS-80 systems, so I have very little knowledge of their common problems or failures. This machine is a particularly important one due to the low serial number, and I would like to see it restored and working.
    Any help anyone can give is appreciated.

  2. #2

    Default

    Welcome to the Model II, the system collected by the masochists of the TRS-80 world!

    I would next check your power supply voltages at the card cage. You might have a weak 5v. The M2 Technical Reference Manual has the pin out for the 80 pin connectors. Also, you mentioned rearranging the cards, but the cards need to be in a certain order. The ref manual and Notes and Jumpers has the details.

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