Question about Toshiba Televison & Video

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My Toshiba Thunder 29G3SH has a failing vertical deflection circuit - the picture has been reducing gradually and is now covering only one-third of the screen at the middle. Could you suggest solutions or better still help with the service manual?

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  • gwseje Apr 28, 2010

    Good evening
    Thanks for the response and the suggested solution. All the capacitors, including C306 have been replaced and there is totally no change. More suggestions are needed beside the service manual which will speed up the repair.
    Regards

  • gwseje May 02, 2010

    Good evening
    I have replaced the capacitor even though the voltage was OK. Still the problem persists.
    Voltages are 28.87 V dc at pin6 and 28.97 V dc at pin 3.
    Any other possibilities?
    e-mail: gwseje@gmail.com for sending service manual
    Regards

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Hi,
Q301, TA8427K that is used for vertical deflection in this tv, please replace electrolytic capacitors C320 (100UF 35V), C308 (220UF 35V) and C305 (2.2UF 16V) to fix picture size issue.
Let me know your email address to send you schematics pdf copy.
Hope this info will help you.
Thanks.

Posted on Apr 27, 2010

  • 1 more comment 
  • Shahid Electronics
    Shahid Electronics Apr 28, 2010

    Good evening
    Thanks for the response and the suggested solution. All the capacitors,
    including C306 have been replaced and there is totally no change. More
    suggestions are needed beside the service manual which will speed up the
    repair.
    Regards
    ================================================================

    Good evening,
    Check +27 volt on pin-6 of vertical out chip.
    If its less then +27 volts, replace C310 (1000UF 35V)



  • Shahid Electronics
    Shahid Electronics Apr 28, 2010

    Check volts on IC pins as shown in below image.




  • Shahid Electronics
    Shahid Electronics May 02, 2010

    Good evening
    I have replaced the capacitor even though the voltage was OK. Still the
    problem persists.
    Voltages are 28.87 V dc at pin6 and 28.97 V dc at pin 3.
    Any other possibilities?
    e-mail: gwseje@gmail.com for sending service manual
    Regards
    ====================================================

    OK, please check input signal level at vertical output chip and also check resistors of reference signal at output terminal.
    Schematics is being sent to your email address.
    Thanks.



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How can i Set Haier tv, my haier 14'' CRT change With 21'' CRT so vertical Hight is short, how can i adjust vertical hight.. IC "Trident TDA 11105 PS/V3/3/AP3


You can check it by reducing the value of the resistor, connected to ground at one end of the deflection yolks' vertical scan out windings. Usually, this resistor will vary a value of 1.2 Ohms to 2.2 Ohms. But, if you reduce this value too much, to say at about 0.15 Ohms or so, there is a possibility of damaging the vertical scan output IC.
So, do this very carefully. It is a trial and error process.
Check it with gradual reducing this value of this resistor; by 0.25 Ohms at a time. Wish you success. I hereby advice you, assuming that the horizontal width of the picture is OK.
If you wish to get some details; check the site linked here. Viewing it in "Mosaic" or "Magazine" will make surf easy Pull up older posts. Surf the site with patience.
http://electronicshelponline.blogspot.com/

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1 Answer

I have a tv that has line going side to side


The line is horizontal but means no vertical deflection (set deflects picture from middle to top and bottom.

Either bad solder connections at vertical output chip or a bad part somewhere in that circuit.

Jun 16, 2012 | Toshiba 26 inch HD monitor TV, DVD and VCR...

1 Answer

One line horizontal onscreen


This is well known problem with the Toshiba line, the problem is in the vertical deflection circuits, it causes the picture to collapse to a flat white line, the vertical output ic and two to three capacitors need to be replaced to correct the issue.

Jan 19, 2011 | Toshiba MD20F51 20 in. TV/DVD Combo

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Verticle lines appearing near top. Reminiscent of more extensive problem a few years ago that repair man said were related to electronic equipment used nearby such as vacuum cleaner. He fixed it with...


Case 1:
If the horizontal lines are red, green or blue or white, and are slanted about 15 degrees up going left to right, they are "vertical retrace" lines. These are caused by the beam current in the offending gun being left on while the vertical deflection is retracing from the bottom to the top on its way to start drawing the next frame. The usual cause is the CRT screen setting being too high (too bright), but (rarely) it could be something wrong with the vertical blanking circuit. Since it is dependent on vertical position, I would check the power supplies feeding the vertical deflection circuit and the CRT bias voltages, especially if they share the same filter capacitor.

Case 2:
If the lines are true horizontal, and colored similarly to the picture (sometimes alternately white and colored the same as program material), the top of picture is folded over itself because of over-voltage distortion ("clipping") in the vertical drive. In this case, reducing the height of the picture also reduces the fraction of the picture with the lines, and may eliminate it. If you are unable to get a full-height picture without the lines, then you should check the vertical deflection circuit for leaky capacitors (also check the power supply voltage going to it).

Case 3:
Several times I've observed bright white lines with random interruptions at the top of a picture supplied by the local cable company. These often occur on one or a few channels for a time (once or twice I've seen it on all channels), and go away after a while. This is a glitch in the cable service.

Case 4
You have a zone of weird colors at the top of the screen. This is probably caused by magnetization of the shadow mask inside the front of the picture tube that is not being erased when the TV is first turned on. Check to see if somebody left a magnetized object on top of or above the TV (look behind the set also). If you find something remove it, turn off the TV, wait a few minutes, then turn it on again. (Explanation: the TV has an internal demagnetizing coil that operates only when you first turn it on. It uses a self-heating temperature-dependent part to gradually reduce the alternating current going through it to override and "fade out" any stray magnetism in the shadow mask.) If the internal demagnetizing (AKA degaussing) coil isn't strong enough, you'll need that "ghostbuster" gadget again. If you don't find an external magnetic source, the internal coil may have slipped out of place at the top of the picture tube and is too far away from the shadow mask, or something is wrong with the degaussing circuit.

If none of these cases match what you see, try a more detailed description of the lines and I'll give it another shot.

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1 Answer

Vertical line


Hello,

Most probably the vertical deflection amplifier is failing. The most common part that fails is the vertical output transistor.
The set is too old to find documentation on part numbers and descriptions. Probably the part is no longer available and you will need the assistance of someone who can help you find an equivalent transistor that will do the job.
Of course, without testing we cannot be certain the failure is the output transistor. It could be from something else such as the voltage regulator that feeds the dc line to the vertical section. Could be the vertical synchronous level that goes too low to trigger the vertical sweep generator.

Other bad parts in vertical deflection circuit though there are not that many parts that would kill the deflection entirely.

Loss of power to vertical deflection circuits. Check for blown fusable resistors/fuses and bad connections.

Loss of vertical oscillator or vertical drive signals
Good luck.

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1 Answer

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Hello,

CAUTION: To prevent damage to the CRT phosphors, immediately turn down the brightness so the line is just barely visible. If the user controls do not have enough range, you will have to locate and adjust the master brightness or screen/G2 pots.

A single horizontal line means that you have lost vertical deflection. High voltage is most likely fine since there is something on the screen.

This could be due to:

Dirty service switch contacts. There is often a small switch located inside on the main board or perhaps accessible from the back. This is used during setup to set the color background levels. (On some sets, this is located on the CRT neck board and may be a jumper plug or other means of selecting service mode - not an actual switch.)

When moved to the 'service' position, it kills vertical deflection and video to the CRT. If the switch somehow changed position or got dirty or corroded contacts, you will have this symptom. Flip the switch back and forth a couple of times. If there is some change, then replace, clean, resolder, or even bypass it as appropriate.

Bad connection to deflection yoke or other parts in vertical output circuit. Bad connections are common in TVs and monitors. Check around the pins of large components like transformers, power transistors and resistors, or connectors for hairline cracks in the solder. Reseat internal connectors. Check particularly around the connector to the deflection yoke on the CRT.

Bad vertical deflection IC or transistor. You will probably need the service manual for this and the following. However, if the vertical deflection is done with an IC, the ECG Semiconductor Master Substitution guide may have its pinout which may be enough to test it with a scope.

Other bad parts in vertical deflection circuit though there are not that many parts that would kill the deflection entirely.

Loss of power to vertical deflection circuits. Check for blown fusable resistors/fuses and bad connections.

Loss of vertical oscillator or vertical drive signals.

The most likely possibilities are in the deflection output stage or bad connections to the yoke.
Good luck..

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You had parts in the vertical deflection circuit failing, most common are the vertical output IC and possibly several capacitors also in the same circuit.

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1 Answer

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Sounds like vertical deflection circuit problem. Could be as simple as a bad solder joint around a heavy component such as a transformer, a bad capacitor, overheated resistor, bad IC or transistor, or combination of these. Repair would require knowledge and experience.

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HYUNDAI COLOUR TV HCT3740 (37CM)


No vertical is always an affordable fix.
- failed (dried out) electrolytic caps in the vertical circuit
- failed vertical IC
- failed power to the vertical circuit.
Hope Ya Fix It

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1 Answer

TV Picture Reduced to Line across the Middle


This is called field-collapse. Either

1. The problem lies in the vertical deflection voltage-doubler circuit. The usual fault is a single capacitor of 100uF/35V that has failed. It is normally connected to a rectifier diode right at the vertical IC. Replacing the capacitor usually gets it working perfectly again.

or

2. The vertical drive IC has failed.

If you are finicky around technical work, then a reputable local repair shop in your locality should do it quickly for you and charge only labour.

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