Do you use the deleted "death" capacitor?

Discussion in 'Amp Tech Center' started by max_twang, Mar 29, 2020.

  1. max_twang

    max_twang Tele-Afflicted

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    I have a couple of blue molded 0.47uf / 600 v caps that were removed from
    Fender Champs.

    Does anyone reuse these on the board as replacements for the blue or brown
    "turds" that people seem to hate? Is there any reason to do this, assuming the
    blue molded caps are within spec.? By the way, I don't have a way to test them...

    Thanks :)
     
  2. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Sure - it's pretty rare for the blue ones to go bad. If you need to replace one, put it in and see what happens.
     
  3. max_twang

    max_twang Tele-Afflicted

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    Thanks Corliss, that's what I thought I remembered reading but wasn't sure...
     
  4. Dacious

    Dacious Poster Extraordinaire

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    They're good caps - Fender must have had a big stock because my late 83 has one. People carry on about replacing the brown caps but really, they're not any better or worse than anything else Fender used.

    People are convinced they are a reason late CBS amps sound 'bad' but it's just incidental they were used at the same time as CBS screwed with the circuits and used some less optimal speakers and certain other bits.
     
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  5. Paul G.

    Paul G. Friend of Leo's

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    The problem with the brown caps is not that they sound bad, it's that they go bad. They seem to be prone to absorbing moisture and usually start to leak DC. You don't HAVE to replace them everywhere, but if you have them between the PI and output, definitely get them out of there. If they start to leak DC, you lose bias and very bad things can happen. My personal amps do have them all replaced with Sprague 715s. They sound like a Fender and are quite reliable.
     
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  6. schmee

    schmee Doctor of Teleocity Silver Supporter

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    Yeah, I use any of those Blues... Not convinced the Turds are bad caps though. The Blue ones shaped like the Turds (later than the turds?) seem like good caps too.
     
  7. sjoko

    sjoko TDPRI Member

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    I don't agree ,....the old blue molded caps are "paper-foil capacitors" ,....and specific these caps can attrack moisture ,... that's why they are molded ,...to keep them airtight .
    But after so many years , heating up and cooling down in the amp chassis , they are not airtight anymore , starting slowly to attrack moisture , which makes it leaking. ( internal current leaking )

    The blue and brown , less fancy caps are just ordinary polyester capacitors ,....they normally will last for ever. ( which is the most important :) ) , so you better can leave them in .

    Another misunderstanding :
    I hear so many times : "these capacitors are the best , they make your amp sound so very good ,..... etc , etc.... ".

    A capacitor does not change any sound at all , as long as it is of the same value ( electrical value ) .

    There is no something like a "magical" capacitor , ...no mattter how fancy , shiny and beautiful it looks .

    The best thing to do is : Take the old blue or black molded paper-foil capacitors out of your amp and just throw them in the trashcan. :D
    Replace them for ordinary polyester/epoxy capacitors ( it will make your old Fender amplifier much more reliable )
     
    Last edited: Apr 1, 2020
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  8. sjoko

    sjoko TDPRI Member

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    just good enough ....:D
     

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  9. King Fan

    King Fan Friend of Leo's

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    25C9673A-CB63-47B4-8818-FAEC6E68F450.jpeg

    Yep, there's life after 'death'... :)
     
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  10. max_twang

    max_twang Tele-Afflicted

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    That is pretty much what I was thinking of doing :) I plan on installing it and hoping there's no leakage. Got some backup parts on order from AES too.

    By the way, I recognize that gut shot. Isn't that the blackface Vibrochamp you rehabbed?
     
  11. sjoko

    sjoko TDPRI Member

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    If you should re-use these old , and old fashioned , ****ty blue molded caps , and you should use these for coupling capacitor(s) to the control grid(s) of the final stage in your amp ,.....then you are gambling with the life-time of your amp !
    You even might DESTROY not only your final stage tube(s) , but your output transformer as well.

    Believe it or not , ...old "blue molded caps" are paper-foil capacitors , and that type of capacitors getting unreliable over decades of years. ( just the same reason for very old electrolytic capacitors , which have to be replaced as well )

    There's only one place where they belong ,.....and that's in the trashcan ! ;)

    Nowadays there are capacitors available which have only the "looks" of these "old blue molded caps".
    ( for those people who like to keep the original looks at the inner side of the chassis ,
    but in fact these new blue types are ordinary , modern and reliable polyester/epoxy capacitors. )

    ( ...i.m.o. "superstition" should be out of place here , ....there are no good - or bad sounding capacitors , ....they simply don't excist .) :)

    ---------------------------

    But ,...of course it's your amp after all , ....you may do whatever you want with it. :)
     
    Last edited: Apr 2, 2020
  12. King Fan

    King Fan Friend of Leo's

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    You nailed it... :) I still play it all the time, it still sounds great.
     
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  13. max_twang

    max_twang Tele-Afflicted

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    So I have a question for you then...

    When you encounter a nice blackface or early silverface Fender amp, do you routinely replace all the molded blue caps with new parts? Whether they are out of spec or not?

    I do this as a hobby, not as my profession, so I don't have the extensive experience that professional techs have. That is why I ask. It has been my understanding, from reading here, other websites and tube amp books, that the molded blue caps are quite durable and do not need to be changed as "routine maintenance." I'm not referring to electrolytics. I realize those should be routinely changed.
     
  14. 24 track

    24 track Doctor of Teleocity Silver Supporter

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    the purpose of caps is to allow A/C current to pass through and not D/C current, as caps dry out they leak D/C so even if a cap reads with in tolerance a 60 year old cap may very well be bad and cause more issues than not . just food for thought!
     
  15. sjoko

    sjoko TDPRI Member

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    My answer : Yes ,....I replace them all , just for the reasons you can read here above.
    I have to give WARRANTY on my work !
    These repaired and overhauled amplifiers will be used daily by musicians .
    Reliability is a "MUST" !


    ( Just for those people who have'nt any understanding of electronics :
    You also neihter leave obsolete , 20 years old ACCEL spark-plugs in the engine of your car , because these spark-plugs still have that shiny , fancy , yellow colored porcelain :rolleyes: )

    ....come on ! ....
     
    Last edited: Apr 3, 2020
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  16. Chipss36

    Chipss36 Tele-Meister

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    Blue molded caps were polyester film ..
    Paper? Where did you ever get this info from?
    They were made by pacific bell, and was a cap way ahead of its time...
    I have researched them, as has sozo! Extensively.

    how many vintage blue molded caps have you tested that showed leakage or esr?

    I use a stancore capacitor analyzer,
    I have yet to see even one with any leakage at rated voltage on a blue molded cap...not one!
    Not sure where you are getting you info from.... because I have tested many, and have very good gear to do so....
    Show me a blue molded cap with leakage...with good test gear...
    And it will be a first!
    They are all I use in my blackfaced amp builds....
    My amps have been toured a great deal, run In recording studios ,
    and well over 20 years...
    Just saying.

    a shotgun approach to replacing caps on vintage amps without need, is flat out just hacking!
    Sorry but this a major pet peeve I have.
    And does a great disservice to a vintage amp owner in many ways...
    But what ever, I am the guy that can make it right again, and do so properly.

    for real, come on!



     

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    Last edited: Apr 3, 2020
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  17. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    We aren't yet at the point where we should just be replacing all the components of an amp. In another 50 years, it could very well be that time.

    My issue right now is plate resistors. More and more and I'm doing my "general service" and then firing it up and getting the bacon frying sounds. Do I want to just start replacing plate resistors in every vintage Fender I touch? Not particularly. But do I want an amp coming back to me in a couple weeks with noise issues? Nope.

    Do all electrolytics, then see what it needs from there. Sometimes the answer is "not very much"
     
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  18. King Fan

    King Fan Friend of Leo's

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    Obviously, vintage amp country is a lawless frontier of pure opinion. I imagine that's why the first sticky in every forum contains this guideline, "Post opinions not facts: Always respect other Forum members opinions even if they clash with your own. Give others room to have differing opinions. Don't state your opinion as FACT."

    So... I like to look for a universally-known expert (eg, Merlin). Failing that, I tend to rely on the consensus of local experts -- the many well-known folks who post logical, test-based, experience-based opinions. What I see from experts here and on other forums is to try to re-use blue-molded caps; most but not all experts who test them and re-use a lot of them seem to find that relatively few leak.

    Every antique capacitor site I've read agrees that molded *paper* caps are unreliable — sadly for the guitar-cap guys, this includes black beauties and bumblebees. I have the strong impression that blue molded 'Ajax' caps are not paper. I've never done a destructive test to find out, but I agree Sozo likely did, and they say, "as in the original, polyester film was chosen." Polyester is pretty stable....

    So in my *opinion* it may be a good idea to try to re-use old blue 'Ajax' caps.
     
  19. King Fan

    King Fan Friend of Leo's

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    While we're discussing opinion, you're right the 'brown blobs' (polite name) are *way* less popular than the blue molded *or* even the later dark-blue blobs. My reading on classic cap sites says the 'blobs' were both early example of molded, encapsulated polypropylene caps (like modern OD 715/716), so (expert opinion seems to say) the brown are not actually unstable, like yellow Astrons, it's just they're polypropylene, which -- even more pure opinion :) -- some cap-sniffers like less than polyethylene for these bigger, eg coupling-cap, slots. Also, they're ugly (opinion is cruel). So you'll see quite a few respected sources here who note you don't really *have* to replace brown blobs -- but for sure you won't get slagged much if you do... :D
     
  20. Lowerleftcoast

    Lowerleftcoast Tele-Holic

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    Would you please just... Shush!

    I've been trying to get these guys to send me those old outdated ****ty blue molded useless caps. I have offered to pay for the shipping. I haven't received any yet and with the comments you have been making, I may never receive any.

    So please keep your comments to yourself...
    :lol::lol::lol:
     
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