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SX-828 with wind noise

Discussion in 'Pioneer Audio' started by Matt Mincer, Dec 8, 2018 at 1:58 PM.

  1. Matt Mincer

    Matt Mincer AK Subscriber Subscriber

    Messages:
    127
    Location:
    Chicago
    Hey All,

    I had posted earlier about this 828 and popping in the low filter. I replaced C31, 32, 37, & 38. That took care of the popping but I was getting a ton of wind noise. I replaced all of the 2SC1312s and all of the 2SA725s but am still getting the same noise. I didn't replace the FETs because I don't have them. B+ is stable and it doesn't matter which input is selected. Also, if I remove the pre in/out jumper, the noise goes away, so I'm pretty sure it's on the front end. The noise is coming from both channels equally and volume and balance don't have any effect on the wind noise. A couple possible clues, the left bass pot is noisy though Deoxed all of the pots. The Audio Muting switch causes a speaker pop a lot like the low filter did before the repair. Finally, when I power the unit there's a bit of speaker pop too. Does anyone one have any ideas? My next step would be to recap the whole board but I don't want to do that if there's a simple fix.

    Thanks
    Matt
     

     

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  2. john stumpf

    john stumpf AK Subscriber Subscriber

    Messages:
    669
    Location:
    philippines
    i did one of those a few years back i know about the noises you speak of. sadly im not much help. this is because as it all basically worked as received i went ahead and replaced ALL the transistors with the recommended replacements as i did the re cap. i could hear the ocean surf gradually subside as i rebuilt each board so i dont know WHICH cased WHAT! have you worked on the af board yet? those 2sc458's need to go to as they are on the top ten list of faulty transistors they get replaced with ksc1845. i grew up in evanston,
     
    Last edited: Dec 9, 2018 at 6:15 AM
  3. rcs16

    rcs16 Super Member

    Messages:
    4,057
    Location:
    Baldwin, Ontario, Canada
    if it is the jfets, then it is weird that they both go noisy at the same time. But it is possible.
    fader lube f5 for pots,
    I have a QX-9900 same issues, almost certain popping is leaky ecaps. One day, in the mean time, I do not mess with those switches :)
    speaker popping during audio mute is a sign of a possible leaky ecap, should be using low leakage Nichicon UKL.types only.
    speaker pop at power on, I would guess is a DC offset adj issue in the amp, or leaky ecap at the input as well, more UKL or film caps(best) for that position.
    The PS could be going noisy, certain ecaps used for filtering the supplies worn out.
    To be honest once they start acting up, re-cap the whole thing (or at least in sections) and then re-evaluate to see if that fixes the issue, determine then, if you need to go to the next step and replace semis etc. if it is a simple thing to change a old bjt, then go for it while you are in there.
    It is a lot of work, but the new ecaps are so much better than those old ones.
    I use Nichicon UKL or film for CEANL,CSZA positions and UKA or film for signal paths, UPW or other low ESR types for DC filtering.
    Switches are big problem on these old units.Very hard to clean and get that silver oxide tarnish off.
    Some times it is nice to say it is that exact component, but once you have it all apart, you want to change them all so that you do not have to go back in there again, if possible

    Good luck.
     
    Last edited: Dec 9, 2018 at 10:11 AM
    slimecity likes this.
  4. EastPoint

    EastPoint Factory Code No. 4200 Subscriber

    Messages:
    4,662
    Location:
    Milwaukee, WI
    I was working on an SA-900 that had a VFET go bad while I was working on it. Suddenly had a ton of hiss/rushing on one channel. Swapped it out and all good now. Weird that you're getting it on both sides. You sure all your pinouts are good on the transistors?
     
  5. slimecity

    slimecity Super Member

    Messages:
    3,066
    Location:
    New Zealand
    Agree - if its in both channels - look here.
     

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