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Advice on replacing some mid80's caps

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    Advice on replacing some mid80's caps

    I recently picked up a an old Apple //c color monitor from 1985. I noticed the color controls were quite touchy, so I opened it up to see how hard it would be to get the pots out to clean them. And I saw a cap that looked like the top was bulging pretty good.

    So out the logic board came, and now I'm looking to recap the whole thing just to be safe. Unfortunately, Apple didn't believe in board level repairs, so schematics are non existent. I had to go through and inventory it manually, and have no idea where in the circuit any of these really are to even guess what type I should replace them with.

    The majority of the caps appear to be some purple wrapped Samhwa caps? Which I had never heard of. Some have series markings on them (mostly SA, a couple GA's, an HR, and a couple with no series markings. I can't seem to find much info on them. Am I OK to just really use most any series from the trusted brands (Panny, Nichicon, UCC)? Should I stick to general purpose, or go low ESR/High frequency?

    There was also a yellow sleeved Samhwa RM series cap. I think that means its a special "low leakage", cap correct? I think the main modern replacement for that is the Nichicon KL series?

    There was also a handful of caps that at first I thought were UCC caps, based on the logo. But it looks like they say Samyoung, or maybe even Samsung inside the logo? The printing is kind of hard to read on the logo, but they were SM series.

    Here is the cap that triggered all this. Pretty sure my ruler should be sitting flat on top of this. Its a snap in cap with a plastic top. Not sure how much more before this thing was going to crack open. Unless this is just how Samhwa made their caps. But I doubt that.



    Thanks!
    Attached Files

    #2
    Re: Advice on replacing some mid80's caps

    here's one
    Attached Files

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      #3
      Re: Advice on replacing some mid80's caps

      Originally posted by stj View Post
      here's one
      Except that is samwha. I'm talking about samhwa.



      Plus I'd guess that datasheet is at least 2 decades newer than this cap, at least.

      I've only worked on one other CRT before, and it did have a schematic and parts list. It had a cap on the deflection board that was also yellow jacketed (but at least it was a brand name cap), and was called out as being low leakage on the parts list. Can't be a coincidence this board has one too. But I could be wrong. I don't know how CRTs are designed. I just know how to discharge them and replace components in them.
      Attached Files
      Last edited by nick3092; 06-16-2020, 07:23 PM.

      Comment


        #4
        Re: Advice on replacing some mid80's caps

        well given what was available then, try using a rubycon YXF

        Comment


          #5
          Re: Advice on replacing some mid80's caps

          Originally posted by nick3092 View Post
          There was also a handful of caps that at first I thought were UCC caps, based on the logo. But it looks like they say Samyoung, or maybe even Samsung inside the logo? The printing is kind of hard to read on the logo, but they were SM series.
          Samyoung capacitors are not related to Samsung. The SM series should be general purpose, so pretty much any replacement will perform well. Use a Panasonic FC if you want something better than an ordinary replacement or a Rubycon YXF as already suggested.

          Use high ripple capacitors on 100/160/250V areas, such as Rubycon BXA.

          Use specific capacitors for the horizontal section as it is a very important area. A wrong capacitor in the horizontal section will lead to failure. Take a pair of photos of that area in order to know which series/type to use.
          Last edited by Hitto; 06-23-2020, 05:18 AM.

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            #6
            Re: Advice on replacing some mid80's caps

            Originally posted by Hitto View Post
            Samyoung capacitors are not related to Samsung. The SM series should be general purpose, so pretty much any replacement will perform well. Use a Panasonic FC if you want something better than an ordinary replacement or a Rubycon YXF as already suggested.

            Use high ripple capacitors on 100/160/250V areas, such as Rubycon BXA.

            Use specific capacitors for the horizontal section as it is a very important area. A wrong capacitor in the horizontal section will lead to failure. Take a pair of photos of that area in order to know which series/type to use.
            Thanks for the advice. I actually just finished the recap last night. I used a mix of Nichicon and Panasonic. I usually stick to those two, but have used Rubycon and UCC in some applications when needed. Nothing against them, I just try to stick to two brands so I'm not spending hours comparing caps across 4 vendors.

            I usually stick to FC or FR when I go with Panasonic for general caps. I also used some Nichicon UPM and UPJ for some caps where FC or FR's weren't an option.

            In general, I always try to look for a good balance of ripple and lifespan. For the higher voltage caps, I went with a mix of UCY, UCS and UPW. I did use a Nichicon KL low leakage to replace that yellow sleeved one. I didn't want to take the chance that it was just a fluke the sleeve was yellow. Worst case, I don't think a KL would have a negative impact. All I know is it looks like it was directly connected to the flyback.

            I didn't have a schematic for this monitor, so I couldn't guess what section each cap was in (short of the two big filter caps where the power came in).

            I didn't notice any major issues during the 10 minutes or so I tested it out yesterday. So hopefully the caps I picked weren't too bad of choices.

            I noticed that most of these Samhwa caps felt incredibly light compared to the replacement caps. Many of them didn't even have the vent relief cuts in the top either. Just smooth metal. I'm guessing they were the cheapest option back then.

            Comment


              #7
              Re: Advice on replacing some mid80's caps

              Nichicon's PM series (lead-free version of the PL series) and PJ series are fairly old, as is the PS series (lead-free version of the PR series). Nichicon is pretty accommodating of customers using older series on their mature products. Chemicon, Panasonic, and Rubycon obsolete older series earlier than does Nichicon (except Rubycon's YXF series, which I think is pretty mature).

              As a whole, I don't think you'll get into trouble replacing older general purpose with newer general purpose (and sometimes can "upgrade" from an 85C part to a 105C part). Newer special-purpose parts probably won't cause problems. It's the low impedance and ultra-low impedance parts you need to be careful with. A part with significantly lower impedance could cause loop stability problems in a power supply or DC-DC converter (output capacitors).
              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.
              ****************************

              Comment


                #8
                Re: Advice on replacing some mid80's caps

                I'm looking for a place to get some Panasonic FM/FC/FR caps, but want to avoid fakes from eBay. Is there a way that I can order caps in small quantities for not too much money in shipping and guarantee that they're real?

                What I generally do is wait until I have many things to recap, then order from DigiKey or Mouser in bulk(ish).

                Better yet, are there any local distributors that I can buy from?

                Comment


                  #9
                  Re: Advice on replacing some mid80's caps

                  try Element14

                  Comment


                    #10
                    Re: Advice on replacing some mid80's caps

                    Originally posted by NeillEvans View Post
                    Is there a way that I can order caps in small quantities
                    It is not economically viable to buy small quantities. Just buy 20 from each capacity and stockpile them. For example 470uF/25V can replace without any problems 470uF/10V, 470uF/16V and 470uF/25v. Caps can stay on the shelf for year and more. They don't require water or food.
                    Buy 20 pieces from each capacity.
                    1, 2.2, 3.3,10,47uF 63V - used in computer PSU-s.
                    100, 220, 330, 470, 680, 820, 1000, 1500uF - 25V(35V) - used on motherboards
                    1800, 2200, 3300 uF - 16V used on motherboards
                    680, 820uF - 63V - used in inverters inside LCD monitors.
                    And you have inventory that covers 80% of the cases, If you repair computers.
                    If you have money, add 100, 220uF 450V - used in computer PSU-s and LCD monitor PSU-s.
                    Usually if you replace 10V cap with 16V cap it lasts longer.
                    Last edited by televizora; 12-17-2020, 02:29 PM.
                    Useful conversions. I don't "speak" imperial. Please use metric, if you want to address me.
                    1km=1000m=100000cm, 1inch=2.54cm, 1mile=1609.344meters, 1ft=30.48cm 1gal(US)=3.785liters, 1lb=453grams, 1oz=28.34grams

                    Comment


                      #11
                      Re: Advice on replacing some mid80's caps

                      Originally posted by televizora View Post
                      It is not economically viable to buy small quantities. Just buy 20 from each capacity and stockpile them. For example 470uF/25V can replace without any problems 470uF/10V, 470uF/16V and 470uF/25v. Caps can stay on the shelf for year and more. They don't require water or food.
                      Buy 20 pieces from each capacity.
                      1, 2.2, 3.3,10,47uF 63V - used in computer PSU-s.
                      100, 220, 330, 470, 680, 820, 1000, 1500uF - 25V(35V) - used on motherboards
                      1800, 2200, 3300 uF - 16V used on motherboards
                      680, 820uF - 63V - used in inverters inside LCD monitors.
                      And you have inventory that covers 80% of the cases, If you repair computers.
                      If you have money, add 100, 220uF 450V - used in computer PSU-s and LCD monitor PSU-s.
                      Usually if you replace 10V cap with 16V cap it lasts longer.
                      You skipped some very commonly used values:
                      4.7uF
                      22uF

                      All in all, Excellent list , thank you

                      Comment


                        #12
                        Re: Advice on replacing some mid80's caps

                        Originally posted by goodpsusearch View Post
                        You skipped some very commonly used values: 4.7uF...22uF
                        You are right. There are also some non standard capacities used.
                        But for Motherboards, it's mostly 470,1000, 1500, 1800, 2200, 3300 and sometimes, rarely, 4700.
                        Last edited by televizora; 12-20-2020, 06:45 PM.
                        Useful conversions. I don't "speak" imperial. Please use metric, if you want to address me.
                        1km=1000m=100000cm, 1inch=2.54cm, 1mile=1609.344meters, 1ft=30.48cm 1gal(US)=3.785liters, 1lb=453grams, 1oz=28.34grams

                        Comment

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