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Thread: DEC RL01/RL02 emulator doesn't work with DE10-Lite board

  1. #11


    The problem seems to be fixed. It might be the problem of the RLV12 controller. I replaced 74S124 (E135).

    As Lou said, the VRLB diagnostic gave no error. Then, I replaced all 75113 and 75107B, but write operation still crashed the disk image.

    I re-adjusted C66 with VRLB and found the best position of it was unstable although reading operations of both emulated and real disk was no problem. So, I replaced 74S124 with PDIP SN74S124. Then, the problem of write operation disapeared.

    I don't know why, but the RL01/RL02 emulator works fine.


  2. #12
    Join Date
    Mar 2008
    Westchester County, NY


    Congratulations on your troubleshooting work and repair! I see E135 in the prints and understand why you looked there when you noted an unstable clock.

    I have noticed in the past a strange behavior of C66. Sometimes I would have to adjust it back and forth and back to its original position to get the clock to oscillate. I wonder if these tiny variable capacitors get dirty or absorb ambient moisture and change capacitance.



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