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    Help with capacitor substitution for a DVR

    I have a DVR that I was replacing the fan in, and noticed one of the capacitors on the power supply board had failed (all others are fine). It was slightly domed with the bottom pushed out. It's a Rubycon 2200μF 10V MCZ - so it's ultra low ESR. Since these have been discontinued, there isn't a direct replacement. I've tried finding something with similar specs, and what I think will work is the RNL series from Nichicon - specifically this one. It's the same capacitance, slightly higher voltage rating (which I understand is fine), and the diameter is the same, slightly shorter (height isn't critical here anyway). I think the ESR rating is okay - the Rubycon is rated to 9mΩ and the Nichicon for 8mΩ. It's the ripple current rating(s) I'm not sure of, and possibly other things I'm not aware of/overlooking.

    Basically is this a good substitute, or does anyone have a better recommendation?

    Thanks in advance to all that respond.

    #2
    Re: Help with capacitor substitution for a DVR

    was the dvr new?
    i cant imagine MCZ in a psu.

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      #3
      Re: Help with capacitor substitution for a DVR

      It's a DirecTV DVR HR21-100 made in March 2008 (by Thomson).

      It has six MCZ series on the power supply board, and five of them on the main board. Both boards have other various model capacitors - a very quick look shows some ZL and ZLH Rubcon's among a few other makes.

      The HR20-700 DVR (made by Pace) that was their first that had MPEG4 support (circa 2006), also had ultra low ESR capacitors on both of its boards (this one has a combo power supply/main board and then a tuner board). Those had issues with the "capacitor plague" though, and those capacitors were replaced a few years ago.

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        #4
        Re: Help with capacitor substitution for a DVR

        That is a great replacement capacitor you have found!
        ESR matches well and the ripple current rating is almost 3 times better.
        I must agree with stj though, very strange with ultra low ESR caps in a power supply.
        But if that is what they used the replacement will work more than well
        "The one who says it cannot be done should never interrupt the one who is doing it."

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          #5
          Re: Help with capacitor substitution for a DVR

          *if* the psu managed to handle MCZ i wonder if it would run with cheap polymers???

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            #6
            Re: Help with capacitor substitution for a DVR

            I've attached some pictures of the power supply board from an eBay listing - it appears to have all the same capacitors. So, it doesn't seem to be from someone else previously replacing them. I have two more of these (same model) that I'll be replacing the fans in as well, so that should further confirm they're original.

            The only voltages I know for sure it outputs are +5VDC and +12VDC (which is standard) for the hard drive. The other connector doesn't have the voltage(s) printed on the board, and uses the same color wire for all its connections. They are likely 3.3VDC or less for the Broadcom CPU, RAM, and other supporting components.

            The one that failed is in the cluster of four to the right of the transformer between two voltage regulators. The front two in that group are the same value - the one the failed is the one closest to the transformer. The other MCZ series capacitors on the power supply board and main board are all 1000μF 16V.
            Attached Files
            Last edited by hitokage; 07-14-2019, 07:57 AM.

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              #7
              Re: Help with capacitor substitution for a DVR

              I sincerely doubt you need so high end capacitors.
              Most likely it was some overstock capacitors they had, or someone used them instead of other capacitors.
              I mean, you typically need these ultra low ESR capacitors to be soldered as close as possible to the circuit board, as close as possible to the switching regulator IC or transformers to keep the current loop as small as possible.
              Leaving such long leads on those capacitors kind of defeats the purpose, the extra wire length adds resistance and a very tiny amount of inductance

              Should be fairly safe to use FM, FR series from Panasonic, KZE from United Chemi Con...

              Also ...2200uF 10v is kind of in between... the psu outputs 12v, 5v and probably 3.3v ... so a 10v capacitor is most likely used to filter 5v or 3.3v, so you can easily use a 6.3v rated capacitor.

              So this would probably work : https://www.digikey.com/product-deta...198-ND/3998084

              And this 1800uF 6.3v capacitor would probably be just fine : https://www.digikey.com/product-deta...9-1-ND/5180935

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                #8
                Re: Help with capacitor substitution for a DVR

                The cluster two 2200μF caps are close to the circuit board, it's the 1000μF that aren't. I'm sure it's not just them trying to use up overstock ultra low ESR capacitors - at least two different manufacturers (Pace & Thomson) and models (HR20-700 and HR21-100) have them. Looking at some of the other power supply boards listed on eBay, the revised version of this DVR (HR22-100) from the same manufacturer (Thomson) also has the same capacitors. I don't know what the design reasoning is, just that's what it has. The plan at this point is to replace both 2200μF capacitors in this DVR - unless after opening up the other two HR21-100s I find a more extensive amount of failed capacitors.

                I have a few other makes and models here that I will eventually be checking for these type of problems, so I'll see what they used. I have a Samsung made version of the HR21 and a Humax version of the HR24 model.
                Last edited by hitokage; 07-15-2019, 01:23 AM.

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                  #9
                  Re: Help with capacitor substitution for a DVR

                  Given that this is a product that users are likely to use in ways that make for poor heat dissipation and, IIRC, MCZ is a 2000-hour rated capacitor, I wonder if the slightly higher impedance of KZE, FM, HE, or ZL parts might be a good trade-off for a much better rated life.
                  PeteS in CA

                  Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
                  ****************************
                  To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
                  ****************************

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                    #10
                    Re: Help with capacitor substitution for a DVR

                    After having a brief look at all the other DVRs, two the exact same model and three others, none of them had visibly failed capacitors.

                    Part of the reason I'm leery with substitution is knowing there was what the design engineers had wanted and then what was actually used due to cost reduction measures. Straying from what was used likely takes it further away from what the original design specifications.

                    While longer rated capacitor lifetime would be good, it would be pointless unless I recap the whole thing, which is beyond what I want to get into.
                    Last edited by hitokage; 07-23-2019, 06:10 AM.

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                      #11
                      Re: Help with capacitor substitution for a DVR

                      there is nothing "cost reduction" about MCZ, they were the very best of the best when they were made - they werent cheap!

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