Question about Toshiba 51H93 51" Rear Projection HDTV

1 Answer

Horizontal output transistor failure

The horizontal output transistor on my 51H93 TV has shorted several times, taking out the circuit fuse.

What could be causing this?

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  • JHD923 Apr 17, 2008

    Where could I obtain one of these mods?

  • JHD923 Apr 23, 2008

    Thanks, scott201201. Do you know of a third-party that would have information on these mods? I tried contacting Toshiba several times at several numbers, but they couldn't help me.

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Check b+ comming from p/s. also check for blue flat caps in line with h-output circuit. if blown out the side. remove them from circuit. also might have a HVT goin bad. I believe this is also the model that might have a mod for h-out running too hott that requires adding a resister in the h-drive circuit. also try a heavier duty h-output.

Posted on Apr 09, 2008

  • Scott Henderson
    Scott Henderson Apr 17, 2008

    i have only had to do one of them, but you can contact toshiba and talk to them, let them know that this is your problem and their tech know about it, and you would like the kit.

    or you can replace it with another h-output useing heat sync compound. but i would say use a stronger h-output.

    the right fix is the kit and i would ask to speak with tech support.

    if you can't get to them then ask for parts dept and have them look up your part number.

    good luck.

  • Scott Henderson
    Scott Henderson Apr 23, 2008

    http://www.tritronicsinc.com

    i think they have a kit for it, but to get the correct part number you may have to ask them. if they dont know get with me

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Its 2 times blink error code that shows +B volt supply (+135 volts) is shorted, most probably horizontal output transistor is shorted, replace it.
If you are good in soldering parts in circuit board then take out horizontal transistor, check it, found shorted then replace it with same number.

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ALL the next is with the tv unplugged (NO NO power)
  • resold the jungle (video processor) all around
  • following the horizontal drive pulse path and arriving to the horizontal area just after the horizontal transformer and in the base of the horizontal DRIVER there is a electrolytic capacitor (if this chassis uses this one,) Change it (maybe is dry)
  • solder all components i just told you in the last step. horizontal driver, transformer, etc
  • remember:
  • if a transistor is blowing with no reason (there is a reason: the collector receives 130 volts but cannot hold it forever, It has to be in some place. if the switching pulse doesn't arrive to it the transistor throws this 130 volts and burning itself. i hope it is help full.

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1 Answer

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This usually indicate a problem with the flyback, or the horizontal output transistor. Most TV problem is not repairable by the user, because of it's complexity. If you like reading, and honestly like to learn on your own, it is not so hard to learn to fix electronic device such as TV. Unfortunately a TV is not something you can look at and figure out how it works. I would suggest start by reading electronic books, preferably the ones with projects to help you learn how electonic device are put together to make a working circuit. The most I can help you with is look for the horizontal output transistor it is square with 3 pins, and is mounted on aluminum heatsink to dissipate heat. One of its pin would be connected to the flyback and the horizontal yoke.(The yoke would be the copper winding on the neck of the tube) be careful you don't touch the thick wire from the flyback to the back of the tube because a tv tube can carry large amount of lethal charge even if not plugged in! Take that transistor out of the circuit and test it with an ohmmeter. Set the meter to "diode" with the transistor facing you. the first pin is the base. Connect the red wire to that then the black pin should read around 0.4 voltage drop it maybe a little highe on the other two pins.. If you get a reading that is low it is shorted out. Note tho that some horizontal output transistor have a resistor connected to the first, and last pin (base emmiter junction) then it gets confusing. If in doubt just replace it. The cost of a horizontal output transistor is around a few bucks. Make sure you buy two of them! If the TV turned on after you raplace it but later failed again. You have to replace the flyback too. This time use your spare transistor along with a new flyback, which cost from 20- 50 dollars. Hope this helps.

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1 Answer

Zenith


First, locate the horizontal output transistor. This is found very close to, or next to, the horizontal output transformer (also known as the flyback). The flyback should be on an aluminum heat sink, or on the side of the metal chassis. Disconnect or unsolder two of the three legs of the transistor. Measure it with your meter, or plug in the set with the light bulb attached across the fuse.
If the transistor is shorted, or the light bulb doesn’t glow bright anymore, replace the transistor and plug back in. If the light bulb glows bright again, you must replace both the flyback and horizontal output transistor simultaneously. In some cases this will fix the set, but sometimes there are multiple problems with a set.
Go to where the flyback is, and start measuring the diodes and capacitors on the flyback itself. If you don't find any shorts there, it could be a shorted vertical output IC, a shorted sound IC, a shorted disc capacitor in the Hi Voltage/sweep circuit, or in rare cases, a shorted capacitor or tuner.Feel free to ask and post whatever the result of your troubleshooting..


Hope this may help;

Regards,
VOTIT

DON'T FORGET TO RATE

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1 Answer

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What's the question???

If the transistor has failed, it has to be replaced. The cause must be found and fixed before applying back the power, or the new replacement will probably soon fail.

Jerry G.

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1 Answer

Toshiba 51H93 .


check for cracks in the driver circuit, also i believe this maybe on of the models that had a kit that helped from driving the h-output to hard causing it to get hotter then normal.

Apr 11, 2008 | Toshiba 51H93 51" Rear Projection HDTV

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