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  • Illinois capacitors

    I have a Peavey VTM 120 I recently got. I see the caps are majority Illinois brand. I was planning on changing most of the caps - especially the filter caps - but the amp isn't that old and I wanted to know what people thought of the quality of these caps.

  • #2
    OH, a lot of folks don't like them, on the other hand, if your amp is working well and sounding good, why tear it apart and do a lot of soldering on it.

    It is one thing to say some brand of cap doesn't last as well as another, but it is not the same as saying that brand always fails. Most Illinois caps don't fail.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      The vast majority are absolutely fine. Their ESR seems to be a little higher than some other makes but not a problem in this application. I suspect this and that fact they are factory fitted is why some people dislike them and just look for any reason to change caps.

      In general it seems to me that everyone wants to replace caps just because of the 'net noise and often without good justification.
      Experience is something you get, just after you really needed it.

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      • #4
        35-40 years old? Change them. All Illinois filters caps are garbage in my book. I change them faster than i take off a set of Firestone tires and throw them away.

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        • #5
          Originally posted by nickb View Post
          The vast majority are absolutely fine. Their ESR seems to be a little higher than some other makes but not a problem in this application. I suspect this and that fact they are factory fitted is why some people dislike them and just look for any reason to change caps.

          In general it seems to me that everyone wants to replace caps just because of the 'net noise and often without good justification.
          I agree for the most part. However, there are a couple of things to consider: I've worked on more Fender Hot Rod series amps than I would count, and have found premature failure of the Illinois filter caps to be a fairly common issue in some of these amps. Yet, on many other Hot Rod series amps, they have held up fine and work perfectly. But I haven't been able to find a common thread with which to tie the amps with this problem together. Unless the caps show any symptoms of leakage or degradation, then there is no reason to replace them unless the customer specifically requests it.

          In some of the VTMs I've serviced, the Power supply board can suffer from some heat stress and damage which can shorten the life of the electolytics. Namely, that 10W/400Ω resistor dissipates a lot of heat. a lot. I've never seen one fail, but it butts up against 2 molex connectors and the heat can build up oxide on those interconnects, with increases resistance and those increase heat (so on, and so forth). Bottom line is that, of all the factors that determine whether an electrolytic is working properly, the label is the least important.
          Here, this is an example of a VTM60 from the early 90's. There was absolutely no reason to replace the caps in this example. (Unless it were my amp. In that case I would have found a way to fit Film caps for the power supply)


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          Last edited by SoulFetish; 11-23-2020, 01:56 AM.
          If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

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          • #6
            But I haven't been able to find a common thread with which to tie the amps with this problem together.
            Well, who says there will be one? The HR series is an all time popular line, they made zillions of them. What if 5% of the caps fail, and Fender used them and JoeBlow amps used them. 5% of 100,000 amps is 5000 amps. JoeBlow makes 20 amps a year, he has 1 bad amp.

            We need not assume something in th amp causes this. All the HR amps run similarly warm inside. What if the caps have some certain inconsistencies in the manufacturing process, and it is just the luck of the draw which amp gets the iffy cap?
            Education is what you're left with after you have forgotten what you have learned.

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            • #7
              Originally posted by beedoola View Post
              but the amp isn't that old...
              Originally posted by mozz View Post
              35-40 years old? Change them.
              This^^^^^^^^^^^^^

              I've seen old Mallory and similar caps hold up and do their job for 40+ years. Those Illinois caps aren't up to it in my experience. Especially if the amp hasn't been used for long stretches of time. Replacing all the electrolytics in an amp over 30yo is just smart maintenance. I'm seeing a lot of "reasoning" about the reliability (or lack thereof) of the Illinois caps. I'm not a repair tech but I've seen what I perceive as a disproportionate young failure rate for that brand. Taking everything at face value:

              A lot of people don't have confidence in the Illinois brand caps.

              The service life on electrolytic caps used in guitar amps is typically less than 20 years (whether the amp is used or not).

              Your amp actually IS old. At least older than the service life of some of it's components.


              I'd replace them. All the electrolytics. Don't forget the bias supply caps.

              Film caps can last forever. They should only be replaced if they fail.
              "Take two placebos, works twice as well." Enzo

              "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

              "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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              • #8
                Originally posted by SoulFetish View Post

                I agree for the most part. However, there are a couple of things to consider: I've worked on more Fender Hot Rod series amps than I would count, and have found premature failure of the Illinois filter caps to be a fairly common issue in some of these amps. Yet, on many other Hot Rod series amps, they have held up fine and work perfectly. But I haven't been able to find a common thread with which to tie the amps with this problem together. Unless the caps show any symptoms of leakage or degradation, then there is no reason to replace them unless the customer specifically requests it.
                I concur with the fact they seem to fail in batches. Whether it's use, manufacturing or an environmental thing is not known.

                I see more FBJ's and HRD than anything else. The problem with that is it skews then data toward saying the Ilionois caps are bad. If you look at the failure rate, I don't see a statistical difference.

                I think part of my hesitation in replacing caps is that I suspect many people are doing it just to inflate the bill, or because they don't know better and I don't want to be part of that crowd. I tell the customer about the pros and cons and let them decide.
                Experience is something you get, just after you really needed it.

                Comment


                • #9
                  Originally posted by nickb View Post

                  I concur with the fact they seem to fail in batches. Whether it's use, manufacturing or an environmental thing is not known.

                  I see more FBJ's and HRD than anything else. The problem with that is it skews then data toward saying the Ilionois caps are bad. If you look at the failure rate, I don't see a statistical difference.

                  I think part of my hesitation in replacing caps is that I suspect many people are doing it just to inflate the bill, or because they don't know better and I don't want to be part of that crowd. I tell the customer about the pros and cons and let them decide.
                  I agree, and to Enzo's point too, I'm sure that the the fact that we see these amps more often when they're "broken" can skew ones perception as well.
                  My boss takes the same approach as you, and I do what I'm told (mostly) . While I may lean more towards preventative replacement, I've definitely moderated my opinions on electros after gaining a bit of experience.
                  Plus, a full cap job can add significantly to a customers total bill, so it's prudent to find out what his expectations are (and ability to pay). That might be determining factor in a situation where preventative replacement is undertaken or not.... Which looking back, is pretty much what you already said, but with more words.
                  word soup
                  If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

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                  • #10
                    Originally posted by Chuck H View Post

                    I'd replace them. All the electrolytics. Don't forget the bias supply caps.

                    actually, I'm glad you brought that up. Bias supply caps are one area where it's we'll replace the caps as a matter of service in many instances due to their critical role.
                    This is usually a very quick repair, and the parts are inexpensive.
                    If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

                    Comment


                    • #11
                      This is strictly anecdotal but I don't have enough faith in the failure mode of modern high voltage electro's to make re-capping any kind of hard policy.
                      I've probably said this enough times on here to sound like a broken record but I'll say it again anyway.
                      Amp damage due to shorted caps was extremely rare in any vintage amps I worked on in the 20th century. They just went open and quit filtering or de-coupling. Hardly ever caused any damage other than hum, or a mess if they spilled their guts (again rare). I was much more likely to see 'leaky' non-electro's which sometimes did cause damage as coupling caps to the power tube grids.
                      In the 21st century I started seeing shorted capacitors and damage to circuits caused by electrolytic cap failures. Shorts, arcing, spillage, etc., often causing failure of other components.

                      I don't think it's coincidence that there are also not many applications for high voltage electro's anymore (aside from guitar amps). They're just not widely used enough in industry to keep up the kind of reliability of the 'golden era' (same as tubes).
                      I could be completely wrong, but generally, I'm not as worried about a pre-90's electro failing catastrophically as I am of it's modern replacement doing so. For my own stuff (all pre-80's), I don't replace til they stop doing their job.
                      "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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                      • #12
                        Originally posted by g1 View Post
                        I don't think it's coincidence that there are also not many applications for high voltage electro's anymore (aside from guitar amps). They're just not widely used enough in industry to keep up the kind of reliability of the 'golden era' (same as tubes).
                        .
                        Sorry, I think that's wrong.

                        SMPSs used at 230V mains require high voltage ecaps. Especially where PFC (boost convertor) is required, you need 450V (sometimes 600V peak) rated caps.
                        In my former company we bought tens of millions 450V rated ecaps per year. And we required 50.000 hours of service life with less than 10% failures.
                        These days the best high voltage ecaps are made by Japanese companies.
                        Last edited by Helmholtz; 11-23-2020, 08:38 PM.
                        - Own Opinions Only -

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                        • #13
                          One word - Panasonic. (check the specs)
                          If it still won't get loud enough, it's probably broken. - Steve Conner
                          If the thing works, stop fixing it. - Enzo
                          We need more chaos in music, in art... I'm here to make it. - Justin Thomas
                          MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey

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                          • #14
                            Originally posted by eschertron View Post
                            One word - Panasonic. (check the specs)
                            ..as well as Rubycon, Chemi-Con, Nichicon and maybe others. Most ecap manufacturers offer different quality grades. Go for highest temperature (105C) rating and apply the 10C lifetime doubling rule.
                            Last edited by Helmholtz; 11-24-2020, 02:49 PM.
                            - Own Opinions Only -

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                            • #15
                              That is certainly a large market, but where else are they used, and I can't recall an axial HV E-cap in much anything else in years.
                              Education is what you're left with after you have forgotten what you have learned.

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