Recap My Plexi?

Discussion in 'Let's Talk Vintage' started by Trapland, Mar 5, 2019.

  1. Trapland

    Trapland Well-Known Member

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    Um not really.. I started a thread about finding NOS caps. And dating.

    I didn’t ask anyone if I should recap. Thank you to the couple guys that helped with the OP.
     
  2. Kats

    Kats Active Member

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    Not to belabour the point because I totally understand where you’re coming from, but how about replacing the cans and if you don’t like it, put the old one’s back in?
     
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  3. Calvert13

    Calvert13 New Member

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    Dude PLEASE recap it all. Not only will your amp sound even better and more responsive it’s a lot healthier to the transformers and you don’t need want to have to replace those. You know why this Marshall sounds so much better, it’s the way the carbon resistors have drifted over time, that’s what makes OG amps jems and dudes, just like a lot of OG Fuzz Pedal builds. Your components have drifted in just that special way. New caps will give you a stronger bottom end and more crystal top mids, but it won’t change the overall sound, just more of the feel of it.
     
  4. neikeel

    neikeel Well-Known Member

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    True the amp will probably be safer (although I have had new caps fail too!) but in my experience they nearly always sound (and feel) different. It will be entirely a matter of opinion whether you think it is better or not.
     
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  5. 67Mopar

    67Mopar Well-Known Member

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    Once you've recapped that Marshall, award yourself with a helping of delicious Chef Boy-Ar-Dee Throwback Recipe Ravioli.
     
  6. Miotch

    Miotch New Member

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    Guess I’m weird. I never experienced a noticeably different tone when recapping an amp. It just got rid of the problem then work again as designed.
     
    Last edited: Apr 28, 2019
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  7. cichlid

    cichlid New Member

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    You can put the original caps back in if you don't like the sound, no problem there.

    But, as soon as you hear how tight the amp sounds with good caps, you'll forget all about those leaky old ones.
     
  8. Chris-in-LA

    Chris-in-LA Well-Known Member

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    You can get an ESR meter.

     
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  9. ampmadscientist

    ampmadscientist Well-Known Member

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    If you play the amp, replace the filter caps. Especially bias filter cap.
    If you collect the amp, leave everything original and don't play it.
    It's up to you to maintain it to play it etc.
     
  10. pleximaster

    pleximaster Well-Known Member

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    The best way tho keep the electrolytes fresh is to play the amp on regular basis. Not playing an amp makes thet caps dry out.
    plexi
     
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  11. Trapland

    Trapland Well-Known Member

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    I gigged this amp last Friday with a 68 basketweave full of original T1511s. I did choose to replace the bias caps. It made no difference in tone nor apparent stability. I did bring another amp for backup as always.

    It sounded like heaven.
     
  12. Antoon

    Antoon New Member

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    Just my personal opinion on this: Purely technically speaking ALL electrical components in an amp have a limited lifetime and will fail eventually. Not long ago it was considered common sense to replace those old Phillips coupling caps as a precaution (which almost never fail). Now people are putting them back in. GEC KT66s (or RCA black plate 6L6s) were replaced as 'maintenace', while they can last over a lifetime. All my plexi's have the original filter caps. I do not consider them to be time bombs and I am not dogmatic about replacing them in advance. Only in one specific case I had to replace a 32uf Hunts filter cap directly after the rectifier (that was bulging). Just as I sometimes had to replace burned screen resistors or noisy anode resistors. Of the grey RS 32uf/450V for instance, that are found in early 100Ws, I have never experienced a failure. Many of the remaining (50 year old!) JTM100 PA amps still have them to this day, sounding great. Several professional guitar players that I highly regard consider those RS filter caps to be key to the amazing sound of these 100W plexi's (you do not have to agree of course). They also use the old Mallory filter caps in their BF Fenders. If you measure one of those caps they are usually still perfectly within spec. I do inspect my amps internally on a regular basis but will only replace components if I absolutely have to, and if possible with reformed identical NOS or even used caps.
     
    Last edited: Jun 14, 2019
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  13. Seanxk

    Seanxk Active Member

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    Best purchase in years and it's made in Britain!!, NOS RS 32-32 and the original from my JTM45.
    These are still 50 year old caps though.....



    IMG_2996 (1).jpg IMG_2997 (1).jpg
     
  14. ampmadscientist

    ampmadscientist Well-Known Member

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    The value of the cap changes according to the voltage.
    A cap which tests good at low voltage (cap esr meter) may break down at high voltage.
    Therefore, these little meters powered with batteries are not really accurate for high voltage caps.
     
  15. Im247frogs

    Im247frogs Well-Known Member

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    Brooklyn, Joey!
    I'm really glad we're still dialoguing this...
     
  16. Bob Barcus

    Bob Barcus Member

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  17. Matthews Guitars

    Matthews Guitars Well-Known Member

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    Actually the mechanism in play there is that reapplying operating voltage to the capacitors maintains the condition of the insulative aluminum oxide anodize layer that was formed at low voltages when the capacitor was first made and electroformed. Left alone, the anodisation slowly degrades, which degrades capacitor performance, with capacitance value lowering, ESR increasing, and leakage current increasing.

    The very best way to get maximum life out of an aluminum electrolytic capacitor with wet electrolyte is to keep the capacitor at its rated operating voltage ALL THE TIME. The very best way to kill it quickly is to fully discharge it and store it at elevated temperatures.
     
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  18. ampmadscientist

    ampmadscientist Well-Known Member

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    Why do people post questions when they already have an answer formed in their heads?

    Then when we answer the question, they vehemently reject and berate the answer?
    (no, that wasn't the answer I was looking for!!!)

    There are certain people in the forum who do that pretty often.
     
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  19. Matthews Guitars

    Matthews Guitars Well-Known Member

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    It's simple. If your aluminum electrolytic (wet electrolyte) capacitors are over 40 years old they're on borrowed time and they are not the caps they once were. They need to be replaced.

    No capacitor manufacturer will tell you otherwise. The only exceptions are computer grade capacitors which, ironically, are a class designed for the one class of equipment (computers) that are most likely to be totally obsolete and have absolutely no job to do long before their capacitors wear out. Computer grade capacitors will also eventually time out but their lifespan is a multiple of other types.

    The cost to replace them is much lower than the cost to repair the amp should they fail catastrophically.

    Arguing against replacing old caps that are working is not any different than arguing against changing your engine oil just because it's still oil, or running on bald tires because they still hold air.

    There are good service practices and there are bad service practices. Leaving 40 year old electrolytics in your amp falls in the bad catedgory.
     
  20. ampmadscientist

    ampmadscientist Well-Known Member

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    Black Gate capacitors are also designed to last just about forever...
     

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