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SX-535 Re-Capped, but Buzzing Returned

Discussion in 'Pioneer Audio' started by Natalya, Oct 27, 2018.

  1. Natalya

    Natalya New Member

    Messages:
    8

     

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  2. slimecity

    slimecity Super Member

    Messages:
    3,000
    Location:
    New Zealand
    +1 on shortening your leads. Its good practice to get into.

    Go thru your new caps you put in against the service manual and ensure that all values you put in are correct.

    Also ensure that you didnt accidentally replace a non-polar/bi-polar cap with a polarised one.
     
  3. UncleBingo

    UncleBingo AK Subscriber Subscriber

    Messages:
    1,120
  4. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

    Messages:
    21,088
    Location:
    Bensenville,Illinois
    First, let me say WELCOME to :) Audiokarma, and a BIG Welcome to a fixer in training!!!:biggrin:.

    read the DC voltage at the terminals of each of the 2 big caps. Right across the red bleeder resistors 560 ohms and 2 watts.
    then read the AC voltage at those same two points. You may have to use a "dc blocking capacitor" if the meter doesn't have one.
    That would be a 0.1uf or so film cap in series with the red probe's tip, so the DC voltage does not interfere with the AC voltage reading.

    We are looking at the performance of the two big caps, 4700uf 35v dc.
    Should show + and - 27 volts or so on DC
    and we are looking for the AC voltages (ripple) to compare against each other.
    Hum that is unaffected by any controls, in both channels, could be from this.

    As for the work you did, think about this:
    you left old capacitors and transistors in the audio path - possibly masking the improvements you DID make.

    Have you seen this thread:
    http://www.audiokarma.org/forums/in...x-535-noisy-transistors.809085/#post-11299995
     
    UncleBingo likes this.
  5. Natalya

    Natalya New Member

    Messages:
    8
    The DC voltage was -27 for one, and 17.5 for the other, so that's out of spec. I didn't have a 0.1uf capacitor on hand so I didn't attempt the AC voltage.


    Also, I finally took a video of the noise!

    @Old capacitors & such left:
    I finally replaced all the rest of the capacitors and some more transistors, this time on the Control board and the Equalizer board, so there shouldn't be any old stuff left aside from the super caps.

    [​IMG]


    [​IMG]

    When I ordered those parts I didn't know there was an anomaly with the super caps so I haven't ordered new ones of those yet. There was a leaky cap on the EQ board, so I'm glad I got that replaced.

    Any recommendations on super cap replacements? They have some similarly rated ones on Mouser but I don't want to accidentally get a kind that won't work properly.


    Yes, that's been super helpful! That's the parts list I've used.
     
  6. UncleBingo

    UncleBingo AK Subscriber Subscriber

    Messages:
    1,120
    "Supercapacitor" is an entirely different thing than the large main filters. It's semantic but clarity is important.
     

     

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  7. UncleBingo

    UncleBingo AK Subscriber Subscriber

    Messages:
    1,120
    I typically up the capacitance value (not more than 2X) and then find a capacitor with equal or higher voltage rating that is a good mechanical fit for the clamps (Diameter). If they're soldered to a circuit board
    the pin-spacing becomes critical.
     
  8. Natalya

    Natalya New Member

    Messages:
    8
    Okay the large ones are 35v electrolytic 4700uF. I found these on Mouser:
    https://www.mouser.com/ProductDetail/United-Chemi-Con/EGPD350ELL752MM40H?qs=sGAEpiMZZMtZ1n0r9vR22UhSjrTM10DEMeoEy8g352UMIFj5yixFuQ==
    35V 7500uF 20% Tolerance "High Temp" Electrolytic

    Would these be a good choice, or should I look at something else? Their size is considerably smaller than the originals, but I think I could make them fit because they don't go into a circuit board.

    There are also these Panasonics:
    https://www.mouser.com/ProductDetail/Panasonic/EEU-HD1V682?qs=sGAEpiMZZMtZ1n0r9vR22QGha91sM8wW3OuajDd/hTg=
    IDK if brand is important or not. 35V 6800uF 20% Tolerance "General Purpose" Electrolytic
     
    Last edited: Nov 8, 2018
  9. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

    Messages:
    21,837
    Location:
    Glen Burnie Md.
    Go UP in VOLTAGE to 50V. There's not a lot of headroom voltage wise on the 35V cap. With increase in Todays Line Voltage your Rail Voltages will be close to 35 (within 5V). Best to go to 50V or even 63V. Chances are the new cap will fit inside an old cap case. (Gut the case and run the leads thru the rubber gasket, seal the can case, and wrap the new leads around the old tabs on the bottom and solder in). No muss, No Fuss. And you won't have to mess with spacers, etc. This one will do just fine in the 535. https://www.mouser.com/ProductDetai...EpiMZZMtZ1n0r9vR22TZ4hs%2bw0LzJV%2bpaXgpFVfA=
     
    UncleBingo likes this.
  10. UncleBingo

    UncleBingo AK Subscriber Subscriber

    Messages:
    1,120
    I agree with Larry about upping the voltage, for sure. If this were a valuable tube receiver I would agree with re-stuffing the capacitor cans- in this case, I'd go with the capacitor that meets the specs that is the closest to the existing diameter and skip re-stuffing the cans.
    Something like this: 647-LKG1J682MESBAK
    or this: 647-LKG1J682MESCBK

    Check the diameter of the caps in your receiver and use the one closest without going over, so it will fit inside the clamps. Some self adhesive cork works great for spanning the gap if the new caps are a little bit narrow.
     
    Oldsansui441 likes this.
  11. Natalya

    Natalya New Member

    Messages:
    8
    Hey I looked at the resistors in the photo at the top of the page, between the leads of the big caps, they say 560ohm but I don't know like their wattage? Anyway, with a multimeter they're not reading 560 ohms, one is around 530 the other is like 270. I think I need to replace those too. I'm guessing they're metal film, but I don't know how current works with them. I've seen some like really chunky huge 1ohm resistors or like a tiny small 1M ohm resistor before.
     

     

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  12. LesE

    LesE 110284 Subscriber

    Messages:
    856
    Location:
    Ontario, Canada
    If you haven't lifted one end of each resistor, it's likely that the measured resistance is not accurate.

    If they measure bad after lifting one end, you will need to replace with 560 ohm, 2 W, 5% metal oxide film resistors as per the service manual.

    Screenshot_20181115-151814A.jpg
     
    Last edited: Nov 15, 2018 at 2:46 PM
    Oldsansui441 and UncleBingo like this.
  13. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
    Mamou, Louisiana
    Just curious but when cleaning the controls and switches, did you remove the hex nuts on the controls, especially the volume and balance controls. If those hex nuts are not snug to the chassis, you WILL have buzzing in the audio.
     
  14. Watthour

    Watthour Electron Rancher - JS3600

    Incidentally, consider the tolerance of a component when testing. A resistor rated at 560Ω with a 10% tolerance would be considered acceptable with an actual resistance value between 504 and 616Ω. As LesE alluded, testing in-circuit can quickly reveal shorts, but for value testing the component should be isolated from the circuit (at least one lead lifted). Chances are the bleeder resistors are just fine.
     

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