Question about JVC AV-20420 20" TV

4 Answers

Power problems I am working on a JVC TV model# 20420. The bridge rectifier D911 was replaced. Experiencing problem now where the unit keeps rupturing resistor, R921, a 2.7ohm, 2W. I have replaced it with latger value resistors but it keeps burning out. The fuse remains intact. I suspect that the diode pack may be giving an output higher than is normal, and may need to be reduced, but there is no reference to the value of the output voltage. I measure 164Volts dc. Grateful if you cam provide a solution. I am unable to get the original resistor that was in the unit.

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  • clif7455 Oct 30, 2008

    This advise is insuffiecient. I was expecting some reference to the schematic diagram. I do have a copy of the power section of the diagram and I can send a copy to you if you desire. I am stuck with having working on the unit so long.
    Regards

  • clif7455 Oct 30, 2008

    I have checked part as suggested and it is not showing a short out of circuit, unless it is breaking down under power.

  • clif7455 Oct 30, 2008

    Dear Exp



    I am quite prepared to accept this advice, because it has offered a new approach, though I beleive I have inspected the track side of the board with a hand microscope and did not see any signs of shorts. However, i will do that again.

    Alternatively, if it was a direct short on the tracks, wouldn't the protective fuse had blown?



    I will accept on your response.



    Regards

×

4 Answers

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  • JVC Master
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If there is a short on board, it will probably burn one of the onboard components , and not the main fuse.

Shorts on the main cable or on the power supply area of the circuit cause the main fuse to blow, other shorts doesnt.

However, a short on a pcb is quite unusual, this can be caused by metal dust, a cold joint touching a nearby contact, a broken pcb, and the burnt area can usually be seen and smelled.

I do not think this is a short on board.

You simply have a resistor that keeps burning because of a faulty circuit (eg wrong voltage from a power amp circuit, a burnt capacitor, something that cause a protection circuit to fail, etc.)

If it is the diod , that is easy to test.

You need to locate what is the cause of the overvoltage that keeps blowing your capacitor.

You need to follow the schematics to troubleshoot this.

I do not have schematics for your model. you can download them the following website for free, a free registration is required.

Here is the link to service manual.

If I was you I also would replace the resistor back with one of the same value, that is probably a safety component, and by using a bigger one you risk blowing something else.





Posted on Oct 31, 2008

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  • Expert
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There is somewhere short on the main board and due to that extra current is passing through the electrical components so the resistors are blowing again n again.check some tracks getting short on the main board.
technician at your place is much advisable as on site reparing is much necessary to locate the clear fault on the board.

thanks.
feel; free for further assistance.

Posted on Oct 30, 2008

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  • Master
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Check all the electronic components in the main board,then replace the fault one by checking wit the help of multimeter

Posted on Oct 29, 2008

  • mohammed marika thambi
    mohammed marika thambi Oct 30, 2008

    this could be several different problems doing this. the most common is the convergence circuit going bad. it will run hot

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  • Master
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Do you have the schematic for this TV?

Posted on Oct 29, 2008

  • Jaime Hernandez Oct 29, 2008

    If that resistor is burning, check IC921(STR30134) for a shorted condition.

    I can send you a copy of the schematic diagram if you need it.

  • Jaime Hernandez Oct 30, 2008

    If you have the electronics knowledge you should know why a resistor or fuse blows. If you think the voltage regulator is good then you should be checking for other shorting out parts such as the HOT, FBT, yoke windings or capacitors.

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