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Cap exploded in VCR power supply board

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    #1

    Cap exploded in VCR power supply board

    Wonder if this is the appropriate platform. I disconnected my VCR to be found that it could not be switched on again. Managed to replace 2 swollen caps 450v 2.2uF and 25v 1000uF. As I switched on the VCR, the power came through but lasted only for about 5 seconds followed by an explosion of a cap 50v 47uF. I was certain of the correct polarities. Moreover, the exploded cap was the original cap on the board. I replaced the exploded cap 50v 47uF but the same thing happened as I switched on the machine. I replaced the cap for the 2nd time. Again it exploded. Which is the culprit? Pls advise.
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    #2
    Re: Cap exploded in VCR power supply board

    Originally posted by william lan
    Wonder if this is the appropriate platform.

    I disconnected my VCR to be found that it could not be switched on again. Managed to replace 2 swollen caps 450v 2.2uF and 25v 1000uF. As I switched on the VCR, the power came through but lasted only for about 5 seconds followed by an explosion of a cap 50v 47uF. I was certain of the correct polarities. Moreover, the exploded cap was the original cap on the board. I replaced the exploded cap 50v 47uF but the same thing happened as I switched on the machine. I replaced the cap for the 2nd time. Again it exploded. Which is the culprit? Pls advise.
    It is better posted here "Troubleshooting TVs and Video Sources" versus a FAQ.

    I'm guessing your caps are exploding because of too much voltage. Maybe a resistor failed? Do you have a multimeter to measure?
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      #3
      Re: Cap exploded in VCR power supply board

      Make, model. What/whose caps did you use for replacement? Need some pics of the unit and problem area(s).

      Toast
      veritas odium parit

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        #4
        Re: Cap exploded in VCR power supply board

        Originally posted by retiredcaps
        It is better posted here "Troubleshooting TVs and Video Sources" versus a FAQ.

        I'm guessing your caps are exploding because of too much voltage. Maybe a resistor failed? Do you have a multimeter to measure?
        I am not a technician but beginning to learn. I have a multimeter just only know how to use it as a continuity, AC and DC check. May be can learn from you how to check the resister but which resister should I check and how?

        Comment

          #5
          Re: Cap exploded in VCR power supply board

          Originally posted by Toasty
          Make, model. What/whose caps did you use for replacement? Need some pics of the unit and problem area(s).

          Toast
          ECE brand, model EVR 248CP was locally cottage assembled. No match in google. Exploded cap was BH/50v 47uF. Will try to post pics.
          Attached Files

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            #6
            Re: Cap exploded in VCR power supply board

            Originally posted by william lan
            ECE brand, model EVR 248CP was locally cottage assembled. No match in google. Exploded cap was BH/50v 47uF. Will try to post pics.
            Just to the left of the exploding cap is what I believe to be a diode standing on end. Could you confirm that one end of it is connected to the transformer and the other end to the exploding cap? If that diode is shorted it could be responsible for the cap exploding. Use your multimeter to check the resistance of that diode. Check it twice, reversing the leads so you check it in both directions.

            PlainBill
            For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

            Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

            Comment

              #7
              Re: Cap exploded in VCR power supply board

              First of all after the first explosion you should have stopped. I am also assuming the two caps you replaced prior were installed with the proper continuity (follow the silkscreen on the board).

              Check the rectifier supplying that cap as PB said if the diode is shorted and feeding AC to the cap it could be responsible for the instant explosion.

              Also check the line cap it's top looks really bulged I've seen those cap tops bulbous before but the one looks a bit too inflated.

              If may just be an insulator but the problem is those tops can hide a cap showing signs of failure.

              Real smart engineering move are those wire wound resistors (on board space heaters) surrounding the line cap and the 2.2uf?
              Last edited by Krankshaft; 07-27-2010, 01:50 AM.
              Elements of the past and the future combining to make something not quite as good as either.

              Comment

                #8
                Re: Cap exploded in VCR power supply board

                Originally posted by PlainBill
                Just to the left of the exploding cap is what I believe to be a diode standing on end. Could you confirm that one end of it is connected to the transformer and the other end to the exploding cap? If that diode is shorted it could be responsible for the cap exploding. Use your multimeter to check the resistance of that diode. Check it twice, reversing the leads so you check it in both directions.

                PlainBill
                Yes, the diode is connected to the transformer on the left and exploded cap on the right. Have checked the diode. It is fine. Any other possibilities?

                Comment

                  #9
                  Re: Cap exploded in VCR power supply board

                  Check the secondary winding supplying caps line for a short.
                  Last edited by Krankshaft; 07-27-2010, 03:03 AM.
                  Elements of the past and the future combining to make something not quite as good as either.

                  Comment

                    #10
                    Re: Cap exploded in VCR power supply board

                    I would suspect a regulation problem. I would replace the small electrolytes near the switch (I suspect this is a 4 or 5 pin IC, right?). Replace those and start up the supply IN SERIES with a light bulb.

                    Comment

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