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Running TV chassis

Discussion in 'Electronic Repair' started by [email protected], Apr 12, 2006.

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  1. Guest

    KV27TS27. Refuses to quit, but now it has gone through another CRT and
    SBX1437. I do not want to put the fourth CRT into a set this old. Damn
    thing won't quit though.

    After some capping and soldering, what might be the life of this
    chassis ? Without the load of the CRT, might be awhile huh ? OK, my
    intent is to turn a working TV chassis into a sophisticated diagnostic
    tool.

    Understand what you have in a regular TV chassis, Houtput collector
    drive can be capacitively coupled to almost any HOT or HVOT circuit,
    thing is it must be regulatable by a control.

    Modifications for HDTV might include sending the fly less B+, just
    build a regulator. Might want a higher frequency but we'll burn that
    bridge when we cross it. I am sure without geometry concerns or
    anything else we can probably tackle it.

    In a regular TV chassis we have waveform generators for most functions
    of a similar (NTSC) set. We can replace the yoke drive, the sound
    carrier, sandcastrle is almost standardized for NTSC now too. With the
    old style video outputs we can replace cathode drive to the CRT(s).

    Nothing says you can't hook a Sony chassis up to a completely different
    yoke and tube. Something that requires little if any dynamic geometry
    correction by the chassis. With the input synched to the output, you
    can now test any signal path. You can inject HF drive to flybacks
    (LOPTs), yokes, all of it. Test them at actual working voltage,,,,,,,,
    and dare I say it,,,,,,,,, beyond. Accelerate troubleshooting of
    troublesome intermittents. got a HV arc, crank it up, what arcs first
    has arced it's last. Think I'm kidding ?

    Why not ?

    To be able to apply high voltage to those things that deal with high
    voltage should be a very useful diagnostic tool. Even more valuable
    might be an old Zenith 25GC45 chassis, the ones that would run the Hout
    into a shorted tripler until the circuit breaker tripped ?

    Now something like that could also supply about 6 Kv AC, which could be
    rectified and used to test focus circuits etc. It might also be better
    if there is a really catastrophic short in the HV to hit it with 5 or
    6Kv at first. If the problem isa obvious then, you have saved not only
    the cost of another Hout transistor, but also the time to procure and
    replace it.

    Even on the Sony chasis, I could drive the flyback with like 4 2SC5150s
    and use an active crowbar "Zener" type circuit for voltage protection.
    Of course I would get rid of the Sony SMPS immediately. I might let it
    run the signal section though, I don't have all year. I want knobs
    connected to potentiometers to control the current limit and the
    voltage. I can design said circuit. It is not that difficult at all.

    We would literally have all kinds of pulses etc. to choose from, and
    demodulation, although it may be less useful, have it and not need it
    then. Byproduct.

    Now you can really test a CRT, see the condition of the screen. Know
    for sure if the yoke is good, and find those pesky intemittent arcs.

    I know many techs have analysers and all that, but this is something
    that will probably get discarded. I can apply the vertical waveform to
    the yoke, leaving the original yoke in the circuit and simply not
    connect the feedback.

    If I hook up speakers I can detect a sound carrier on NTSC.

    It also has a remote detector which could be connected somehow to give
    a visual indication. You DO remember getting pay channels on cable by
    resistoring the H pulse to the IF circuit I hope. Those in the know
    know you need to slow the time constant of the IF AGC as well.

    Anyway, I mean as a service tool. I think it would be great.

    Whaddya think ?

    JURB
     
  2. JANA

    JANA Guest

    You are going to a lot of trouble to make a jig for troubleshooting TV sets.
    Using a good scope and DVM should be adequate for most of the problems.

    If you use another chassis Horiz HV drive output to drive another one in
    another set, there is the issue of impedance matching.

    Also, CRT type TV's in a few more years, are going to be scarce for finding
    new ones, and especially parts for them. Most people are no longer having
    their older sets serviced. They are simply replacing them.

    --

    JANA
    _____


    KV27TS27. Refuses to quit, but now it has gone through another CRT and
    SBX1437. I do not want to put the fourth CRT into a set this old. Damn
    thing won't quit though.

    After some capping and soldering, what might be the life of this
    chassis ? Without the load of the CRT, might be awhile huh ? OK, my
    intent is to turn a working TV chassis into a sophisticated diagnostic
    tool.

    Understand what you have in a regular TV chassis, Houtput collector
    drive can be capacitively coupled to almost any HOT or HVOT circuit,
    thing is it must be regulatable by a control.

    Modifications for HDTV might include sending the fly less B+, just
    build a regulator. Might want a higher frequency but we'll burn that
    bridge when we cross it. I am sure without geometry concerns or
    anything else we can probably tackle it.

    In a regular TV chassis we have waveform generators for most functions
    of a similar (NTSC) set. We can replace the yoke drive, the sound
    carrier, sandcastrle is almost standardized for NTSC now too. With the
    old style video outputs we can replace cathode drive to the CRT(s).

    Nothing says you can't hook a Sony chassis up to a completely different
    yoke and tube. Something that requires little if any dynamic geometry
    correction by the chassis. With the input synched to the output, you
    can now test any signal path. You can inject HF drive to flybacks
    (LOPTs), yokes, all of it. Test them at actual working voltage,,,,,,,,
    and dare I say it,,,,,,,,, beyond. Accelerate troubleshooting of
    troublesome intermittents. got a HV arc, crank it up, what arcs first
    has arced it's last. Think I'm kidding ?

    Why not ?

    To be able to apply high voltage to those things that deal with high
    voltage should be a very useful diagnostic tool. Even more valuable
    might be an old Zenith 25GC45 chassis, the ones that would run the Hout
    into a shorted tripler until the circuit breaker tripped ?

    Now something like that could also supply about 6 Kv AC, which could be
    rectified and used to test focus circuits etc. It might also be better
    if there is a really catastrophic short in the HV to hit it with 5 or
    6Kv at first. If the problem isa obvious then, you have saved not only
    the cost of another Hout transistor, but also the time to procure and
    replace it.

    Even on the Sony chasis, I could drive the flyback with like 4 2SC5150s
    and use an active crowbar "Zener" type circuit for voltage protection.
    Of course I would get rid of the Sony SMPS immediately. I might let it
    run the signal section though, I don't have all year. I want knobs
    connected to potentiometers to control the current limit and the
    voltage. I can design said circuit. It is not that difficult at all.

    We would literally have all kinds of pulses etc. to choose from, and
    demodulation, although it may be less useful, have it and not need it
    then. Byproduct.

    Now you can really test a CRT, see the condition of the screen. Know
    for sure if the yoke is good, and find those pesky intemittent arcs.

    I know many techs have analysers and all that, but this is something
    that will probably get discarded. I can apply the vertical waveform to
    the yoke, leaving the original yoke in the circuit and simply not
    connect the feedback.

    If I hook up speakers I can detect a sound carrier on NTSC.

    It also has a remote detector which could be connected somehow to give
    a visual indication. You DO remember getting pay channels on cable by
    resistoring the H pulse to the IF circuit I hope. Those in the know
    know you need to slow the time constant of the IF AGC as well.

    Anyway, I mean as a service tool. I think it would be great.

    Whaddya think ?

    JURB
     
  3. John-Del

    John-Del Guest



    I thought you were giving up the Wild Turkey Jeff!!

    I thought about doing that several times, but the chassis are too big.
    It's much easier to build test fixtures and tools using parts of
    chassis (maybe your Sony) than the whole deal. I started building a
    real flyback tester, using a jungle chip, driver XFR, paralled horiz
    outs, and switchable inducters to simulate yoke loading. It's still
    unfinished as most of these projects end up.

    John
     
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