diagnosing crt tv color problem

Discussion in 'General Electronics Chat' started by tpny, Jun 19, 2014.

  1. tpny

    Thread Starter Member

    May 6, 2012
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    Hi, please see attached picture showing a neck board in crt tv. The "G. Drive" and "G. Bias" pots don't work when I turn them - green color doesn't change on screen. Please advice! Thanks!
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Not much information to work with. Why do you think the pots need adjusting?

    ak
     
  3. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    Do you have full on G with retrace lines?
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Green gun emission is down or non existent, looks like an oldie.
    Max.
     
  5. #12

    Expert

    Nov 30, 2010
    16,247
    6,744
    Buy the schematic for that TV and measure the voltages to find any circuit faults or find out the CRT is not working.
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Compare voltages on the R,G,B pins on the tube and see the difference when adjusting the DC pots, it could be the heater on that gun, ideally you need the circuit of the TV.
     
  7. sheldons

    Active Member

    Oct 26, 2011
    616
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    Ok make and model required and I can supply you with a service manual ....unless you start in the correct way you will not repair this fault as colour faults have a number of different causes......it may be nothing on the crt pcb it could be on the main pcb...
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
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    Swap the R and G wires goinf from motherboard to neck board.

    If the fault swaps to RED, the problem is on the motherboard. If the fault rermains on GREEN the fault is the neckboard or CRT.
     
    PackratKing likes this.
  9. sheldons

    Active Member

    Oct 26, 2011
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    Again, make and model then the schematics may mysteriously be uploaded...... my all seeing crystal ball has been sent to the cleaners for calibration
     
  10. vk6zgo

    Active Member

    Jul 21, 2012
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    You beat me too it!
    That's what I always did if one colour was missing.

    Beats chasing through tons of circuitry,when you don't need to.
     
  11. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    You can tell the pros... ;)
     
  12. tpny

    Thread Starter Member

    May 6, 2012
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    It's a toshiba. No marking of a model on the housing. It's like 32" so probably from the 90's.. Thanks for a lot of good guidance above!
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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  14. ian field

    Distinguished Member

    Oct 27, 2012
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    Monitor boards are fairly complex, usually a cascade with complementary pair emitter followers - TVs are *MUCH* simpler, so should be pretty to trace the circuit out by hand.

    CRT flashover is not uncommon, so one of the transistors could be S/C - or at least leaky.
     
  15. tpny

    Thread Starter Member

    May 6, 2012
    216
    0
    turns out the transistor for green on the neck board has cracked solder joints with the board, resoldered and green came back, picture looks great!
     
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