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Oscilloscope problem.

Discussion in 'Electronic Repair' started by Dan Stephen, Aug 27, 2007.

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  1. Dan Stephen

    Dan Stephen Guest

    I have a Hung Chan 6502 20MHz cro that is proving rather difficult to
    repair. Apparently it is also known as a Protek 6502.

    The fault is that the trace is only just visible with the brightness on
    full. This one has me baffled.

    Any advice would be greatly appreciated.


  2. Don Bowey

    Don Bowey Guest

    I'm not at all familiar with that scope, but....... Do you have access to
    the crt cathode, aka Z axis, control? Maybe you have a link, jumper, or
    other Z axis option mis-set.
  3. hr(bob)

    hr(bob) Guest

    Do you have a schematic? Check the various voltages on the CRT. If
    you have a high-voltage probe, measure the accelerator voltage -

    H. R.(Bob) Hofmann
  4. N Cook

    N Cook Guest

    Is the trace equal illumination over the whole trace or is there an X-axis
    gradation in the brightness of trace?
    Is the trace constant in brightness or wavering?
    Did it suddenly emerge as a problem or gradually over time?
    Is the trace of the correct geometry, X and Y sense, for a test signal input
    ? if it is correct then not an EHT problem

    I would suspect leakage/failure in something in the blanking/un-blanking
    area (eg opto-coupler high R resistor) or a "sub bright" preset failure.
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