Dear, I have a Toschiba lcd-TV 42X3000PG. In the power-supply(V28A00036500) their are 2 diodes in short circuit and the main fuse is broken. The 2 diodes are marked with "GA78" ,but i can't find them in any shop, can you help me to know which diode is the replace part? Regards, Guido Beste, Mijn Toshiba LCD-TV 42X3000PG is stuk. In de voeding (V28A00036500) zijn er 2 dioden in kortsluiting en de hoofdzekering op de printplaat (6.3A) is stuk. Op de dioden staat er "GA78" gedrukt ,heb er mee naar verschillende elektronica zaken mee geweest ,daar wisten ze niet over welke diode het ging. Zou je me kunnen helpen met te zeggen waar ik zo'n dioden kan vinden of door welk een type ik ze kan vervangen? Met vriendelijke Groeten, Guido

Hi Jeffrey,
There is some short circuit in the power supply board which is causing this. Do not just go trying new fuses, it may increase the damage. Please consult the TV Tech to take care.
Good luck.

Short circuited component/s at its main power regulator board. Contact any service technician. If you wish to get some details; check the site linked here. Viewing it in "Mosaic" will make surf easy.
http://electronicshelponline.blogspot.com/

Good day!!!!


That problem is cause of shorted bridge diode or power mosfet..

just see the picture below to see the image of bridge diode and power mosfet..



If you don't have a tools or you have no electronic background you only have to is order the new power supply board..

I hope this solution will be helpful..Thanks for using fixya....

Some of the parts of the power is shorted try to check the regulator and the diode. But be sure to unplug the unit before checking the regulator and the diode. Feel free to send feed back good day and best regards.

Hello
There is some short circuit with the power switching regulator section. Check the MOV [Metal Oxide Varistor] connected accross the main AC power line, on board. This device will look like a ceramic capacitor, usually green or black in color. If any voltage spike comes over, this device will get shorted, and the fuse will burn off; thus it is used as a protection against overvoltage and current spikes. If it is alright, check the rectifier diodes or stalk rectifer fitted for any reverse short. You can measure the short very easly by measuring the resistance between the two terminals of the main resevoir capacitor. If this point shows any short, check out the revalent components, including the power switchig device, either it is transistor or an STR, whatever may be. Anyway, there is a direct short in your power supply regulation system of your TV. Get it repaired first, before put a new fuse in place. OK.

The fuse blown because theres a short circuit connection in the PCB power supply of your television.Please check the power supply inside,remove the back cover to see the power supply section.unplug first to avoid electric shock.Will you check the bridge type diode first.If the bridge type diode or diodes is shorted the fuse is always blown.Using digital tester check diodes,regulator transistor,and other transistor around the power supply.

yes this mean there is a dead short, I would look for shorted diodes in the power supply should be at beginning, tracing back into tv circuits

Is that the fuse in the plug , if so what rating, if its a 13 amp wow you have a short circuit probably diodes or capacitor short circuit in power supply, easy to fix usually, but not for the novice

pete

Your filter capacitors have popped due to diodes shorting, P-channel FETs shorting from gate-to-drain. Pull-up resistors have changed value and as a result your capacitors have peaked (popped)....so now the tv is in protection mode to prevent further damage to your tv. Take it to your local shop for servicing, or take it back if its under warranty......

It has a short circuit somewhere...
Not sure if this is a CRT, LCD or Plasma TV but the two common causes of shorts for CRT's are the Horizontal Output Transistor (HOT) and/or the Flyback Transformer (Could be both). As a general rule if the flyback has visible cracks in the case they should be replaced. It is also a good idea to replace the HOT if you're replacing the flyback as it could be weakened and may not last much longer itself.
Other areas to check for all types would be any Diodes in the Power Supply Circuit. If a diode is open it can cause the fuse to blow. Note that a diode itself will not short, but an open diode can cause a fuse to blow.