Question about Toshiba TP55H60 55" Rear Projection Television

3 Answers

No picture,good sound

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About 2 years ago I replaced the stk's (Q751 and 752) which worked till about 2 weeks ago when bent color horizontal lines started appearing intermittently in the middle top of the screen. Last week ,the picture died completely but the sound still works. I replaced the two power amps again(Q751 & 75) but had the same problem. Right now, if the remote is used to power and shut down the TV, the sound will not come on but if the power cord is unplugged then plug in ,the sound will come on but not the picture and also when the TV is turned off, a bright horizontal flash / line on the middle of the screen appears before it shuts off . I checked the power supplies and they seem to be good. I got bogged down by the fact that on pin 11 of Z801 and on pin 1 of P806, schematic says that I am suppose to get 24.7 VDC referenced to GRD and +38 (H.VCC) on pin 1 of P806( also referenced to chassis grd) but I was getting 0.0 volts. I don't see the secondary of the transformer directly referenced or tied to chassis grd so this made me doubt whether this is a printing error or valid reading. Help is appreciated, Thank you.

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Highland Electrix TV Repair Advice no pic snd ok Page Highland Electrix TV Repair Advice no pic snd ok PageNo picture, sound ok

First increase tube's first anode voltage (knob on the loptx) to see if the screen is just too dark.
if after you have turned up the bottom knob on the loptx, there is still no brightness,check, for crt heaters, and EHT 25kv and focus voltage (2kv) and A1's/Screen/G2 voltage is 300-600v.
and check for field timebase (height), the next thing to check is the sandcastle pulse.
If it's present, colour decoder chip is probably faulty or lacks supply from the LT regulators.

Posted on Jul 25, 2008

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Click this for more information:

T.S.S. LOG FOR TOSHIBA updated 4-2-2002

Posted on Jul 15, 2008

  • LORETO LACARON
    LORETO LACARON Jul 27, 2008

    Over time a bad convergence circuit
    could mess up the power supply in the tv.this would make the projection
    tubes have no power, it is possible the main power supply section that supplies
    them is defective. Audio is working, so that section of the power supply seems
    okey.

    Therefore, I suggest you start at the power supply level. There may be a
    fusable resistor in the line somewhere that powers the filaments to the
    projection tubes. If you have a voltmeter you might want to trace the
    filament wiring back to the transformer and see where the power is lost.



    Click below for sample service manual
    with schematic diagram;



    Training Toshiba PLASMA TV PDP 42WP37

  • LORETO LACARON
    LORETO LACARON Aug 01, 2008

    Toshiba troubleshooting;


    No
    picture sound ok


    Note 1 a Raster is the name for a screen made of lines of brightness

    Note 2, A Blank raster has no snow or picture, its just a lit up screen



    Sound ok but no raster.

    First increase tube's first anode voltage (knob on the loptx) to see if the
    screen is just too dark.

    if after you have turned up the bottom knob on the loptx, there is still no
    brightness,check, for crt heaters, and EHT 25kv and focus voltage (2kv) and
    A1's/Screen/G2 voltage is 300-600v.

    and check for field timebase (height), the next thing to check is the
    sandcastle pulse.

    If it's present, colour decoder chip is probably faulty or lacks supply from
    the LT regulators.


    NO LINE DRIVE

    If it's absent,check the line driver, locate the loptr(big
    and usually has heat sink).

    follow the print from the base back to the driver stage , where you will
    usually find a tiny transformer with 4/5 pins

    resolder it, even if it looks good,then with power on, check for voltage on all
    its pins, 2 should have LT(12v to 32v) or HT (90v to 150v), if not there follow
    the print back and look for either a transistor(linedrivetr), or the feed
    voltage line (maybe regulated),

    If the voltage is ok on two of the driver transformer(drvtx) legs, the look
    from the base of the driver transistor to locate the timebase chip

    and check round its pins for a 12v supply line, if there ,replace the timebase
    generator chip

    see NO
    line Drive


    Method of testing line drive, remove line output transistor, and connect a
    normal red led, across the B/E (longest leg to base), and when you power up the
    led should lite up.





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If everything else works - there is sound and high voltage (static on the screen) - but there is no picture (including no on-screen menus), this limits the likely area of problems is the video output circuitry or CRT filament connections. Check to see if the CRT filaments are glowing. If they are not glowing, check for bad soldering on the CRT neck board and around the flyback transformer. Where the picture is erratic - coming and going entirely or changing brightness suddenly, with power off, remove the picture tube socket (carefully!) and clean the pins with fine sandpaper and use contact cleaner on the socket. This source of bad connections can result in a variety of erratic symptoms. Check for bad solder connections on the CRT neck board

Posted on Jul 15, 2008

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