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My Singlepower Supra Experience - Why mine almost blew up like a Hand Grenade (and yours might too)

Discussion in 'Headphone Amps (full-size)' started by tyson, Jul 30, 2009.
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  1. kevin gilmore
    yes that is a bleeder cap across the final power supply cap.
    470k. So that cap will bleed to zero. Will take about 20 minutes.
    If it was just that cap. The regulator fet would pull down the
    rest of the capacitors behind it. Probably to the point where
    the regulator runs out of headroom, then the leakage current
    of the regulator would take over, and it could take a couple
    of days to drain everything that way.

    The best way to add the resistors is to get a couple of ring lugs
    and solder the resistors to the ring lugs. Then after making sure
    the caps are discharged, unscrew the screws and put a resistor
    across each of the big caps.
     
  2. Mher6
    Update for pictures on post #117

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]


    High res: SP Extreme
     
  3. Pars Contributor
    I believe Kevin is saying to put the 100K bleeder resistors across the two large screw terminal caps, as in the marked up pic below. Kevin, correct this if wrong.
    vbattach19281.jpg
     
  4. takezo
    Quote:

    Originally Posted by kevin gilmore /img/forum/go_quote.gif
    yes that is a bleeder cap across the final power supply cap.
    470k. So that cap will bleed to zero. Will take about 20 minutes.
    If it was just that cap. The regulator fet would pull down the
    rest of the capacitors behind it. Probably to the point where
    the regulator runs out of headroom, then the leakage current
    of the regulator would take over, and it could take a couple
    of days to drain everything that way.

    The best way to add the resistors is to get a couple of ring lugs
    and solder the resistors to the ring lugs. Then after making sure
    the caps are discharged, unscrew the screws and put a resistor
    across each of the big caps.




    yes, proper drainage of those giants before even trying to put
    a bleeder resistor on them. it's such a simple thing but wasn't
    implemented in the first place...
     
  5. mrarroyo Contributor
    Pars, what you posted is what I was thinking. Hope others chime in, thanks. BTW, would that be the only thing or should any other "mods" need to be implemented. Thanks.
     
  6. takezo
    that's correct mrarroyo. using a lug is recommended, as kevingilmore suggested, instead
    of soldering directly on the giant cap(s).

    just please make sure you discharge the cap before even attempting to put a bleeder on.
    i usually tape a large value ohm and wattage resistor at end of a glass bead or rod and
    touch the two ends of the resistor on the - and + ends of the cap to discharge quickly.
     
  7. moredes
    Here's a mighty ignorant "dangerous" question... I just finished having to have a bad capacitor serviced on my home's heat exchanger. I just learned how to test it--I was told to remove the capacitor and give it a charge, "any" charge would do--in my case, a 12V auto battery charger connected for say, 30 minutes.

    I was told that if the capacitor was still good, I could take a screwdriver and arc the two posts--if I didn't get a spark, the capacitor was kaput. So to my question....

    In a "live", working, connected system, how would someone drain these capacitors?--just let them stand for a "long" time? If so, how does one test them to insure they've been drained?

    Thank you. I hope this is related enough not to be considered a hijack.
     
  8. kevin gilmore
    Quote:

    Originally Posted by Pars /img/forum/go_quote.gif
    I believe Kevin is saying to put the 100K bleeder resistors across the two large screw terminal caps, as in the marked up pic below. Kevin, correct this if wrong.



    That is exactly correct.

    As far as draining capacitors like this, there is a thing called a discharge stick which you can make yourself.
    In this case 2 good insulated alligator clips connected to about 6 inches of wire with a 10k 5 watt resistor in
    the middle. With one hand and wearing a rubber glove, clip one alligator clip on one terminal, then clip the
    other alligator clip on the other terminal, then wait a minute. Use a voltmeter to verify if you want.

    You will not be able to solder to those capacitors. Even if you could, it would be a very bad idea.
    ring lugs like the ones already there are best. Or wrap the wires of the resistor under the screw.

    ring lugs available in any decent hardware store.

    Adding the resistors is a great safety thing. It guarantees that there is no charge left in any of the power
    caps, and should you accidentally break a tube if you leave it off for an hour you won't risk an electric
    shock removing the parts of the broken tube. Broken tubes happen ask anyone with a fender classic 60.
     
  9. n_maher Contributor
  10. thathertz
    The transformer on my MPX3 is too hot to touch right now
    after about an hour playing a signal. Not sure how long it takes
    to reach this point.

    Is this the case with other MPX3's?
    Is it a serious issue?

    Input appreciated from other MPX3 owners and of course Mr. Gilmore [​IMG]

    P.S. Kevin, are your towels dry yet?
     
  11. kevin gilmore
    Quote:

    Originally Posted by thathertz /img/forum/go_quote.gif
    The transformer on my MPX3 is too hot to touch right now
    after about an hour playing a signal. Not sure how long it takes
    to reach this point.

    Is this the case with other MPX3's?
    Is it a serious issue?




    A number of them get this hot.

    Yes it is a serious issue. Moreso because the transformer in your
    unit is 220 vac. See nate maher's recent thread.



    Quote:

    Originally Posted by thathertz /img/forum/go_quote.gif
    P.S. Kevin, are your towels dry yet?



    you asked for it...
    http://gilmore.chem.northwestern.edu/bathroomsystem.jpg
    and my favorite place to conduct business
    http://gilmore.chem.northwestern.edu/bathroomphone.jpg
     
  12. wnmnkh Contributor
    Wow, Kevin.....

    Is this under-spec component issue only found in some particular lines of SP? I think we really need to check all of SP's models before they make not-so-pretty fire and toast the headphones and sources.

    And I believe we are talking about full-tube amplifiers, not even hybird ones.
     
  13. thathertz
    Quote:

    Originally Posted by kevin gilmore /img/forum/go_quote.gif
    A number of them get this hot.

    Yes it is a serious issue. Moreso because the transformer in your
    unit is 220 vac. See nate maher's recent thread.


    you asked for it...
    http://gilmore.chem.northwestern.edu/bathroomsystem.jpg
    and my favorite place to conduct business
    http://gilmore.chem.northwestern.edu/bathroomphone.jpg




    Talk about 'worth a thousand words'! [​IMG]
    The combined talents of Hollywood could not have produced
    a better image [​IMG]

    Actually my transfromer is 110v and I'm using a heavy duty step-down
    converter Kevin.

    Still an issue though I guess ?

    Just touched the transformer again to make sure I wasn't exaggerating.
    Burns like hell.
     
  14. moredes
    My MPX3's transformer is warm, but definitely not what I'd call "hot", after playing for several hours. I can keep the back of my hand on the cover as long as I like. (the back of the hand is much more sensitive to temerature than the palm-side) Mine is 110V.

    Thank you, Kevin, for explaining the discharge stick!
     
  15. HeadphoneAddict Contributor
    Quote:

    Originally Posted by thathertz /img/forum/go_quote.gif
    Talk about 'worth a thousand words'! [​IMG]
    The combined talents of Hollywood could not have produced
    a better image [​IMG]

    Actually my transfromer is 110v and I'm using a heavy duty step-down
    converter Kevin.

    Still an issue though I guess ?

    Just touched the transformer again to make sure I wasn't exaggerating.
    Burns like hell.




    What happens if you put an egg on the trafo? Does it get cooked?
     
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