Tektronix 465B Focus Problem

Discussion in 'Electronic Repair' started by mike@westendstudio.com, Feb 3, 2006.

  1. Guest

    The traces on my 465B scope are bright but a bit out of focus...I have
    heard of resistor problems in the focus control voltage divider in
    other models that have caused this same problem. I checked the CRT
    schematic and noticed the resistors in question are in a resistor
    network of 4 resistors.

    Any thoughts on this would be helpful.
    Thanks
    Mike Miller
    Kansas City
    , Feb 3, 2006
    #1
  2. James Sweet Guest

    wrote:
    > The traces on my 465B scope are bright but a bit out of focus...I have
    > heard of resistor problems in the focus control voltage divider in
    > other models that have caused this same problem. I checked the CRT
    > schematic and noticed the resistors in question are in a resistor
    > network of 4 resistors.
    >
    > Any thoughts on this would be helpful.
    > Thanks
    > Mike Miller
    > Kansas City
    >



    What's the focus control do when you adjust it?
    James Sweet, Feb 3, 2006
    #2
  3. Guest

    The focus control seems to function correctly, but you can't quite get
    the trace clear and sharp.
    , Feb 3, 2006
    #3
  4. Jim Yanik Guest

    wrote in
    news::

    > The traces on my 465B scope are bright but a bit out of focus...I have
    > heard of resistor problems in the focus control voltage divider in
    > other models that have caused this same problem. I checked the CRT
    > schematic and noticed the resistors in question are in a resistor
    > network of 4 resistors.
    >
    > Any thoughts on this would be helpful.
    > Thanks
    > Mike Miller
    > Kansas City
    >


    The thick-film resistor could be out of spec,or you could also have
    astigmatism problem,or noise in the power supplies.
    First,check the cathode V (-2960,IIRC)to see that it's in spec.Part of the
    thickfilm network is the HV divider that sets the right voltage,part is the
    focus network.(doublesided thickfilm)

    465B was not known for a really sharp trace-it has a mesh lens at the end
    of the electron gun structure.

    --
    Jim Yanik
    jyanik
    at
    kua.net
    Jim Yanik, Feb 3, 2006
    #4

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