On the power supply board transistor labeled VB40 was fried, and the part number is totally illegible. I do not have a schematic for this set. Can someone tell me the part number for this transistor, and maybe an Thanks ECG sub number ?
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The issue you describe is consistent with a power supply board issue. This is the board where the AC goes to. This problem may have occurred as a result of irregular power supply, or excess power supply or power surge.
The TV is receiving current but cannot circulate or transfer the current to other necessary part of the TV because of the defective power supply board.
I do not think it needs replacement, rather some defective capacitors are causing this issue. Open unit up and take a look at the power supply board.You will probably see one or more electrolytic filter capacitors that are bulged up in the top-not perfectly flat like the others.
The value of these capacitors will be different, most likely they will be somewhere around-820 to 2200uF/25 V( or /10V sometimes)
You can replace them with same values but I would recommend the voltage rating to be higher(like 35V for an original 25V) for reliability purposes.
What happens is,these bulged top capacitors will cause a low and unfiltered DC voltage=main board will malfunction(the relay will keep clicking until the caps are holding enough charge to bring the voltage up over a threshold point).
You can buy these capacitors at any Fry's or Radioshack store or you can order them online at vendors like "mcmelectronics.com"(look for electrolytic capacitors). After replacing these capacitor(capacitors) most likely the normal operation will be restored.
Note: There may be also some other causes for this symptom ,like a defective T con board ,or main board,but the bulged top capacitors are the most common cause for this issue.
If you don't know about TV repairers, take the TV to the nearest repairman to fix the fault for you. Also, note that TV stores a lot of current, so wait a while before opening the TV back cover.
Try this: unplug the set and wait about 10 or 20 minutes. This is to make sure that the main power supply filter caps completely discharge. Look on the power supply board, close to where the AC cord attaches to the board. Look for a white resistor labeled "0.1 OHM" (the symbol for OHM, like an upside-down U) and measure it with your ohm meter. If it is open then your switching transistors in the main power supply are most certainly shorted. Older sets had 2 separate transistors on little heat sinks labeled "C4834", then they switched to 2 transistors in one package labeled "MX0841" or "MX0842", and then some sets went to two separate MOSFET transistors. Measure those parts and post your results and we will guide you from there.
if you are replacing 7402
also replace diode 6404 this diode even thou it test goo will in long term overheat 7404 and caus it to go bad by leakage.
and if 7402 gose bad it is regulating the 15v stanby volts that is 7412 is also going to be bad so replace 7412 also
the part numbers are:
7402 = # 932211676682
There should be a part designation written on the board under that part. FOr example Qxxx or Dxxx. Can you post that here please? I can cross reference that designation using the model number to get you the part number, cost and description.
Dead, led flashing red/green at first, then going to red standby
Replace C604 (1000uF, 16v) elec. cap. It is in the decoupling circuit for the 5 volt supply
Red led blinks on / off, TV does not turn via power button and/or remote but after 20 minutes or so it turns on and works fine
Replace R902, R901, R905, R903, R900A, Q902, and possibly the two (one
small and one large) capacitors in the section labeled as the power
supply. The board will be black under the components that are bad. Q902
is an NPN transistor and is hard to find.
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.
Sound not so good. You probably have a bad flyback transistor and now the power supply is fried also.If your lucky all youll have to do if your a tech and only if your a tech is to replace the Hi voltage transformer and the horizontal output transistor. Now these sets have high voltage still around there componets even when the sets unplugged, so please if you wanna invest in the set take it to a pro to assist you in this repair. Good Luck