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OT More vintage electrolytic capacitor problems

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  • #16
    A separate little bridge for the time delay relay will speed up the discharge.
    https://app.box.com/s/auq3jini5c6y73jeo7n5k70h5mt21saf
    If it is industrial, the DC capacitors have to be discharged to less than 50 V in less than 60 seconds.
    (Capacitors over 600V DC have to be less than 50VDC in less than 300 seconds)

    One time I also used an scr with a diac or PUT trigger to short out the charging resistor.

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    • #17
      So you replaced the original filter capacitors with ones that are near twice as large? And you are popping the breaker? And you are surprised!

      Try getting the original values and see what happens.

      BTW, the abbreviation "m" is for milli which means 1/1000th. Almost every electrolytic capacitor that I have ever seen, and in a career in electronics I saw a lot of them, was rated in microFarads or millionths of a Farad. The standard abbreviation for micro is the Greek letter which looks like a lower case, English "u" but has a larger descender. Since most keyboards, typewriter or computer, do not have Greek letters on them, use of the English "u" is an accepted practice. So generally you see microFarads abbreviated as uF.

      Another BTW: the idiocy of some stupid board of so-called scientists that said that even though many units of measure are named after prominent men in the field, the units would be spelled with a small first letter. I consider that to be an insult to the men who were to be honored. And, in the case of the Farad, the microFarad, and the picFarad it has been general practice for many generations to abbreviate them using a capital "F". I have read many thousands of schematics and parts lists and would not even recognize a small "f" as a reference to the units of capacitance. To paraphrase a famous general of WWII, I say NUTS to that stupid board of so-called scientists. It's Volts, Ampers, Ohms, Farads, Henrys, Newtons, etc. These were great men of science and they deserve to have their names capitalized when they are used, even as units of measure.
      Paul A.
      SE Texas

      And if you look REAL close at an analog signal,
      You will find that it has discrete steps.

      Comment


      • #18
        Originally posted by Paul Alciatore View Post
        So you replaced the original filter capacitors with ones that are near twice as large? And you are popping the breaker? And you are surprised!
        Not quite. The Phase Linear 700 uses 9,800uF caps and he says he installed 220,000uF (I presume he meant uF). The Phase Linear 400 uses
        5,600uF caps and he says he installed 100,000uF.
        Location: Long Island, N.Y.

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        • #19
          That's a 20 times increase in capacitance. No wonder the breaker is blowing. I'm giving top marks to the bridge rectifier for withstanding this.

          My stereo system at one time had multiple amplifiers that would pop the breaker every time if they were all turned on at once- which happened because I used a remote box which had only a single controlled outlet. My solution was to build a staggered switching system which was controlled by that one remote outlet. It was interesting to click the remote, then watch the lights dim each time an outlet came on line.

          For a single amp you have no choice but to reduce the charging current during turn-on. What I've done before is to install a relay with double contacts to connect the charging current from the rectifier to the caps, then also have some 10 ohm, 10 watt resistors in parallel with the contacts. The coil is triggered by the voltage on the caps rising above about 80% of the full value of the voltage when the amp is on but still idle. I did this with another resistor sized to trigger the relay at that point, and fed it from one of the two supply voltages. Sometimes there's an additional load taken from the positive supply voltage, so you could wire it to the negative side to sort of balance the loading on the power supply. Using a 24 volt relay will keep this additional load down to about 50 ma, but a 48 volt relay would be more appropriate. Even the 400 will have enough voltage after the rectifier to click on a 48 volt relay (still through a resistor).

          I have rarely found a filter cap in this type of amplifier to go bad, and almost never had to re-form them due to long periods of non-use- but that has happened- and I have been out of the business for 20 odd years now so this has probably become less rare. The cure is to feed the power to the amp through a light bulb for a while before plugging it in directly. Much old gear had this problem, but we're talking pre-sixties for the most part. I don't recall when the Phase Linear 400 came out, but I guess they'd be fairly old by now- I think it would be good to do this re-forming step before using it anyway, just as extra insurance whether it needs it or not. The old Citation amps were brutes as well, and any of the tube amps would definitely enjoy a 'soft re-start' if they haven't been used on a regular basis.

          All of this older gear is going to be suffering from intermittent contacts in switches and controls, so it would be good to spritz them all with a contact cleaner such as NuTrol, then mop up the over spray best as possible without disturbing the components. You would probably have to figure out how to remove the cover from the output relay so you can do a decent job of rejuvenating those contacts as well.

          As far as replacing caps I wouldn't do every one- just those in the signal path (coupling caps if they are electrolytic). That's going to be a fair amount of work just to find them all, let alone remove and replace them without damaging the pc boards. The large electrolytics in the power supply would be the last ones I'd replace, unless they prove to be bad.
          Last edited by darryl; 06-26-2017, 12:44 AM.
          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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          • #20
            Just on a practical basis, I feel sure he installed 22,000 uF as there is not room to install a part 20x bigger.

            Those are plenty big enough, even with the improvements in components. And I will flat guarantee to you that there is one heck of a surge when the switch is flipped (and that switch may not take it for long.).

            It is, by the way, not good to go super-large with the capacitors. Yes, there is extra smoothing, but the rms input current goes up, due to the short charging pulses. The amplifiers do not need that much capacitance. Neither amp is actually that large, power-wise, and the capacitors used in the design are quite adequate.
            Last edited by J Tiers; 06-26-2017, 11:26 PM. Reason: add a space in "the rms"
            4357 2773 5647 3671 3645 0087 1276

            CNC machines only go through the motions

            "There's no pleasing these serpents"......Lewis Carroll

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            • #21
              Originally posted by Paul Alciatore View Post

              BTW, the abbreviation "m" is for milli which means 1/1000th. Almost every electrolytic capacitor that I have ever seen, and in a career in electronics I saw a lot of them, was rated in microFarads or millionths of a Farad. The standard abbreviation for micro is the Greek letter which looks like a lower case, English "u" but has a larger descender. Since most keyboards, typewriter or computer, do not have Greek letters on them, use of the English "u" is an accepted practice. So generally you see microFarads abbreviated as uF.
              That's only half of the story:
              Especially American capacitor manufacturers have been using m for micro. You can also find "mf" in older (american) schematics that denotes microfarads.
              "nano" is also too complicated for americans so they use 22000 pF or or 0.022 uF (mf) instead 22 nF.
              Location: Helsinki, Finland, Europe

              Comment


              • #22
                To add complication,
                In English, the units named after persons do not have the first letter capitalized
                eg farad is correct.

                But when the unit is abbreviated , we use a single capital letter
                eg farad becomes F
                The multiplier is not capitalised, so we have uF

                When I was in engineering school, we were told not to pluralize units
                so it is 100 metre, not 100 metres
                100 microfarad, not 100 microfarads ( 100 uF, not 100 uFs )
                and 10 foot, not 10 feet

                But these days I see so many units being pluralised, and I wonder what is taught now andf if both ways are OK.

                here is a ref for unit names and conventions:
                https://en.wikipedia.org/wiki/Intern...ystem_of_Units

                Comment


                • #23
                  Yes, you would think that someone that readily distinguishes between .1, .01, .001, and .0001 would have no trouble getting the proper number of zeros between 22 and UF, and in front of 1F, but such is obviously not the case here.

                  I suppose I should feel flattered that someone would take my word that I would know how to write what I meant, however this is tempered by the idea that they also think I would use such ridiculous values.

                  In my defense, see quotes from the Newark invoice below. 22000UF = 22000F and how many zeros in front of UF to equal 0.01F.

                  ALUMINUM ELECTROLYTIC CAPACITOR 22000UF 100V 20% SCREW; Capacitance:22000 F; Voltage Rating:100V

                  CAP ALU ELEC 0.01F 100V SCREW; Capacitance:0.01F; Voltage Rating:100V
                  But it all turns out to be a tempest in a teapot. Last night as I was composing this response I went to the shop to check the values on the original caps.
                  While I was there, I thought I would try a different brand of breaker to see if that would make any difference. I have probably 100 - 200 breakers of different sizes and styles that fit into the panel so I have a good assortment to choose from.

                  First I tried a Cutler Hammer 20 amp unit, worked fine the first time. So then I tried a "newer looking" 20 amp GE unit, worked fine, what the heck??

                  So in an effort to either confirm or deny my level of sanity, I re-installed the 20 amp GE breaker that kept tripping, and it's performance was very consistent, it would only stay on if cycled on and off twice.

                  So I put a "newer" 15 amp GE breaker back in and it has worked perfectly since then. We shall see what it does today.

                  Thanks for all the comments, recommendations and education,

                  Dave

                  Comment


                  • #24
                    I remember some old schematics that abbreviated capacitance units as "mF", which I understood to mean what we call uF today, and "mmF", which would be equivalent to today's pF. I don't remember seeing "nF" until more recent years.

                    Ed
                    For just a little more, you can do it yourself!

                    Comment


                    • #25
                      When I was just a kid in the '50's, I helped my father label and sort some capacitors (or condensors as they were usually known) in his radio/tv repair stock. At that time the usual abbreviations were mf and mmf (micro-micro-farads). I nicknamed them mickey-mikes. And, yes, I watched the Mickey Mouse show, but never got my ears. I also liked Annette Funicello, who was sometimes nicknamed "Full of Jello"
                      http://pauleschoen.com/pix/PM08_P76_P54.png
                      Paul , P S Technology, Inc. and MrTibbs
                      USA Maryland 21030

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                      • #26
                        I want to hear that Flame Linear doing Radar Love.

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                        • #27
                          Originally posted by wombat2go View Post
                          I want to hear that Flame Linear doing Radar Love.
                          Wow, you recognized that band?
                          It really does sound great!!

                          The invitation is open to anyone to stop by and have a beer or Pepsi.



                          Dave

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                          • #28
                            Now that you guys have stirred my memory, I believe I do remember that being used in schematics that were old in the 1950s. The "mmF" is what brought it back. I do remember seeing that.

                            With the standardization of the prefixes for all units of measure, that became a real big NO NO.



                            Originally posted by ed_h View Post
                            I remember some old schematics that abbreviated capacitance units as "mF", which I understood to mean what we call uF today, and "mmF", which would be equivalent to today's pF. I don't remember seeing "nF" until more recent years.

                            Ed
                            Paul A.
                            SE Texas

                            And if you look REAL close at an analog signal,
                            You will find that it has discrete steps.

                            Comment

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