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    #1

    Should these caps be replaced?

    Hello,

    I am repairing a linear power supply with a blown bridge rectifier. It has three huge caps that I am not sure are bad. The tops are slightly domed but the vents have not popped. They test 0.01 ohms on my Blue ESR meter and I have no way to test the capacitance since they are 47,000 uF. It looks to me that from the date code they are from 2004 so about 9 years old.

    This is the Digi Key link for the exact same caps: http://www.digikey.com/product-searc...ds=338-2267-ND

    This is the link to the caps I will most likely get if they need to be replaced since they are a lot cheaper and the same basic specs: http://www.digikey.com/product-searc...081?k=P6901-ND

    I have attached the datasheet for both brands of capacitors.

    I am leaning toward just replacing them to be on the safe side but I thought it would be a good idea to get some input from the forum before spending the money. Any constructive feedback would be appreciated.

    Thanks!
    Attached Files
    Tags: None
    #2
    Re: Should these caps be replaced?

    looked domed to me - cant understand why the cornell doublier should be so much more expensive.
    maplins stock that brand - they are similar to radioshack!!
    Please upload pictures using attachment function when ask for help on the repair
    http://www.badcaps.net/forum/showthread.php?t=39740

    Comment

      #3
      Re: Should these caps be replaced?

      They definitely suffered some abuse. I would replace them just to be sure.

      Comment

        #4
        Re: Should these caps be replaced?

        Seems strange that they have bulged, but sometimes with light loads, the power supply rails can go up somewhat, and this occasionally causes this to happen. If it is the cause, get 35v caps if you can, and if you can fit them!...
        Muh-soggy-knee

        Comment

          #5
          Re: Should these caps be replaced?

          Originally posted by selldoor View Post
          looked domed to me - cant understand why the cornell doublier should be so much more expensive.
          maplins stock that brand - they are similar to radioshack!!
          Even if they were the same price I would still go for the Panasonic's, however at $4 apiece cheaper I would be crazy to not get the Panasonic's.

          This supply is a linear 12V that is supposed to do up to 35A. These are 85 deg caps and the tops are almost touching the huge transformer so that could be the problem. This thing is probably heavily loaded when it is being used.

          Thanks for the input, I will go ahead and order them.
          Attached Files

          Comment

            #6
            Re: Should these caps be replaced?

            Originally posted by LDSisHere View Post
            Even if they were the same price I would still go for the Panasonic's, however at $4 apiece cheaper I would be crazy to not get the Panasonic's.

            This supply is a linear 12V that is supposed to do up to 35A. These are 85 deg caps and the tops are almost touching the huge transformer so that could be the problem. This thing is probably heavily loaded when it is being used.

            Thanks for the input, I will go ahead and order them.
            Wait, put them back in and measure the voltage on the capacitors with no load on the power supply. It shouldn't be above the 25v rating of the capacitors. If it is, you will need higher voltage capacitors!
            Muh-soggy-knee

            Comment

              #7
              Re: Should these caps be replaced?

              Originally posted by selldoor View Post
              looked domed to me - cant understand why the cornell doublier should be so much more expensive.
              maplins stock that brand - they are similar to radioshack!!
              I believe cornell doublier is highly regarded in the audio/hi-fi world? I think they are one of the last capacitor manufacturers Made In USA.

              The blue sleeving is/was also used by Sprague.
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              Comment

                #8
                Re: Should these caps be replaced?

                Originally posted by ben7 View Post
                Wait, put them back in and measure the voltage on the capacitors with no load on the power supply. It shouldn't be above the 25v rating of the capacitors. If it is, you will need higher voltage capacitors!
                I appreciate your concern, however I do not think the voltage being too high is a problem. The transformer that is feeding the rectifier is only putting out a little over 14V AC with no load and the rectifier is supposed to have a 1.1V drop. Additionally, these caps are supposed to be surge rated to 32V.

                From the dates I found in this thing it looks like it was made in the mid 90's so it appears to have been recapped once before, so going by this it was due once again.
                Last edited by LDSisHere; 04-10-2013, 03:12 PM. Reason: Added Quote

                Comment

                  #9
                  Re: Should these caps be replaced?

                  Originally posted by retiredcaps View Post
                  I believe cornell doublier is highly regarded in the audio/hi-fi world? I think they are one of the last capacitor manufacturers Made In USA.

                  The blue sleeving is/was also used by Sprague.
                  I have no idea if they are good, okay or bad but I know for sure they are much more expensive at Digi-Key.

                  I was surprised by the USA on the label and by the fact that Digi-Key carried these exact same band\series\size caps.

                  Comment

                    #10
                    Re: Should these caps be replaced?

                    See if those caps are shorted.
                    Last edited by retiredcaps; 04-10-2013, 03:37 PM. Reason: typo/grammar
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                    We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

                    Please do not post inline and offsite as they slow down the loading of pages.

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                    Comment

                      #11
                      Re: Should these caps be replaced?

                      I just can't understand why those caps went bad... they were made by a good mfg, used within its ratings... only thing left would be that they were defective from the factory. I wonder if you could send them to CDE so they could look at them and find out what went wrong.
                      Muh-soggy-knee

                      Comment

                        #12
                        Re: Should these caps be replaced?

                        The 50A 1000V bridge rectifier was shorted when it was given to me to repair. Before I posted on here this morning I tested the rest of the components by using a 8 amp rectifier out of an ATX supply. It worked just fine. I had around 14V DC at the rectifier and approximately 13V DC on the output side of the board.

                        I think the purpose of this thing is to run automotive CB equipment from an AC power source and maybe boost the signal strength at the antenna.

                        Comment

                          #13
                          Re: Should these caps be replaced?

                          Originally posted by LDSisHere View Post
                          I think the purpose of this thing is to run automotive CB equipment from an AC power source and maybe boost the signal strength at the antenna.
                          I was wondering about the RF transistors in one of the photos. Makes sense now.
                          36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

                          Comment

                            #14
                            Re: Should these caps be replaced?

                            Originally posted by LDSisHere View Post
                            I think the purpose of this thing is to run automotive CB equipment from an AC power source and maybe boost the signal strength at the antenna.
                            I was wondering about the RF transistors in the first photo. Makes sense now.
                            36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

                            Comment

                              #15
                              Re: Should these caps be replaced?

                              I got the caps and rectifier in today. I put everything back together and as best as I can tell, it is all working properly. I do not have any way to test the amplifier side.

                              I included a couple of pictures too show how close the capacitors are to the transformer. The top cap was domed the least and the bottom one the most when I removed them. The "small" 10,000 uF was not domed at all, but I went ahead and replaced it along with all the other electrolytics in the supply to prevent any other problems in the near future.

                              Thanks for all the advice!


                              Attached Files

                              Comment

                                #16
                                Re: Should these caps be replaced?

                                Did you toss the old ones yet?

                                If not, it would be cool if you did an autopsy of them
                                Muh-soggy-knee

                                Comment

                                  #17
                                  Re: Should these caps be replaced?

                                  Originally posted by ben7 View Post
                                  Did you toss the old ones yet?

                                  If not, it would be cool if you did an autopsy of them
                                  I am giving all the parts I replaced to the supply's owner so he can see what was replaced. If he gives them back then I will do an autopsy.

                                  Comment

                                    #18
                                    Re: Should these caps be replaced?

                                    Originally posted by LDSisHere View Post
                                    I am giving all the parts I replaced to the supply's owner so he can see what was replaced. If he gives them back then I will do an autopsy.
                                    I'll take that as a no
                                    Muh-soggy-knee

                                    Comment

                                      #19
                                      Re: Should these caps be replaced?

                                      used to see a lot of those with the bridge shorted.idiot cb'ers overloading the front terminals and then overdriving the amp.the whole unit is a pile of crap but they would hold together if you ran them right.

                                      Comment

                                        #20
                                        Re: Should these caps be replaced?

                                        Originally posted by kc8adu View Post
                                        used to see a lot of those with the bridge shorted.idiot cb'ers overloading the front terminals and then overdriving the amp.the whole unit is a pile of crap but they would hold together if you ran them right.



                                        Originally posted by ben7 View Post
                                        Did you toss the old ones yet?

                                        If not, it would be cool if you did an autopsy of them
                                        I got one of these caps back and did an autopsy on it. I found it interesting. Getting the can open without mangling the entire cap was not easy. When I did finally puncture the casing, brown liquid started squirting out and I could hear it depressurize. When I got the "roll" out it looked like it was moldy in some places. Also, I was somewhat surprised that the leads were connected in the middle of the roll.

                                        I hope my pictures show you what you wanted to see. I do not think I have ever intentionally taken a capacitor apart.

                                        Attached Files

                                        Comment

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