Question about Toshiba 51H93 51" Rear Projection HDTV

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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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  • 170 Answers

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

    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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1 Answer

HOT transistor TT 2222burn after second replace. TV Samsung Model CS-21Z45MJ

Before replacing an other one, replace the freewheeling capacitor, the capcitor fitted between the collector of the 2222 and earth; usually of a value of 3500pf 2000VDC, some times this value may differ from set to set. If this capacitor has opened of developed in value, the result will be the failure of the horizontal output transistor, at switch ON itself. The second reason is the short in horizontal yoke windings. Even one winding get shorted, it will cause to a heavy load flyback transormer which in turn to 2222 failure. The last reason for this fault is defective Line Output Transformer itsef. Check these three.
Before proceeding, desolder out the horizontal output transistor 2222 fro circuit, and measure the frequency at the collector point of horizontal driver transistor. It should be around 15625HZ [may differ a little], with no signal. If this frequency is found higher than normal, The main IC jungle should be suspected.
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Standby light blinks seven times. Set will not turn on.

Your TV has a horizontal deflection failure problem. This may be due to Horizontal Output Transformer, or its driver transistor failure. You just do one thing. Disconnect it from AC mains, wait for some time, say 5 minutes or so, then reconnect it again and switch on your TV with its power switch, and see whether it working or not. If not, open your TVs back cover, after disconnecting it from the mains power supply. Horizontal Output Transformer {FBT}, otherwise known as Line Output Transformer [LOT], can be seen prominatly on the circuit board. It is a high frequency stepup transformer, that give all the working voltage to build up screen in the picture tube. It looks like a cylindrical in shape, and one of its wire will be seen sucked to the top of the picture tube with the help of a rubber ******.
Beside the above said LOT, very near to it, will be a transistor, horizontal output transistor, which in turn drives the LOT, can be seen screwed to a heatsink. If thei transistor gets leaked, collector to emitter, or base to collector, whichever may be,it will give an effect of direct short to the secondary positve power supply rail, ie 135vDC regulated supply. This may be the first rason for a seven times blinking in Sony TVs.
The second reason is LOY itself has a shorted winding developed inside. While the above said transitor fault can be measured with the help of a multimeter, LOT trouble cannot be measured by normal methods. If LOT has shorted windings insie, it will also cause a short to the above said supply rail, and will give seven blinks. You just solder out the above said transistor from the circuit board, ad replace it with a same type and humber. Switch on the Tv for a short period of time, say 30 seconds or so, plug it out from the AC mains, and touch with your bare fingers on the trasistor we have replaced, and feel its heat effect. It may be warm, but not too hot. If TV works this time you can make sure that the transistor was faulty.
If it turns very hot during this short period of time, make sure that the LOT has got damaged. Replace it with the same type and number. OK.
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If horizontal output gets shorted always, something may be wrong with Line Output Transformer [LOT], or deflection yoke. If LOT windings inside is short, hrozontal output transistor will get overheated, and will be get shorted soon. If there is winding short in the Deflection yoke, even a sinlgle winding gets shorted, it puts a great load on LOT, which in turn effect horizontal output transistor. The third main reason for horizontal output transistor failure is due to an open or dry solder at the capacitor connected to its collector to negative It will be usually 2500pf to 3500pf, according to the TVs screen size. You just check these three and be sure about the fault.

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1 Answer

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1 Answer

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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.

Horizontal output Transistor Q502 number is 2SD2578 and available in Part Store for $10
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1 Answer


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.

Apr 16, 2008 | Televison & Video

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

1 Answer


Yes, you should check other parts. The horizontal output transistor is more than likely shorted. Also the flyback could have gone bad. Some SONYs have problems with the horizontal driver transformer which is connected to the base circuit of the horizontal output transistor. If this little transformer has a loose solder connection, it will take out the horizontal output transistor. This may give you some insight as to where to look for your problem. Stargazer

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1 Answer

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The most common problem with TV was the failure of the Horizontal Output Transistor, this will also damage 2 transistors in the power supply and a resistor in the power supply also. (From memory): Horizontal Output location # Q501, 2 power supply transistors Locations Q601, Q602, and resistor Location R607. Also solder the Horizontal drive transformer, you can find it by following the circuit board from the base of the Horizontal output. Some models used an IC instead of the 2 transistors in the powersupply, it will have six legs and check like 2 transistors. Good Luck.

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