2230 - hum noise with Phono

Discussion in 'Marantz Audio' started by ssouci, Nov 17, 2012.

  1. ssouci

    ssouci Well-Known Member

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    just finished fully recapping my 2230, and trying it out...

    I noticed that when input is in Phono position (no turntable conected since I don't own one), I get an audible hum noise... sounds like a fairly deep-sounding 60Hz... this sound will increase/decrease with the volume control

    the phono board was fully recapped, plus transistors replaced, plus diodes replaced, plus the central cap boosted in value to 220uF

    btw I noticed a similar sound in the (unused) Tape position, however it is much less intense and not as low

    what would cause this please? thx!
     

     

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  2. ChrisMarantz

    ChrisMarantz Super Member

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    Do you have shorting plugs in the unused input jacks?
     
  3. ssouci

    ssouci Well-Known Member

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    shorting plugs??? what are those pls.
     
  4. bktheking

    bktheking Gitter Done!

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    They look like the end of a rca plug with no wire coming out. Better for you to try a turn table to determine if there is a problem. The Phono could be picking up chassis hum, did you try flipping the power cord around to see if it goes away?
     
  5. ssouci

    ssouci Well-Known Member

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    can I make these up somehow?...

    I will also try reversing cord
     
  6. avionic

    avionic " Black Knights " Subscriber

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    Last edited: Nov 17, 2012
  7. bktheking

    bktheking Gitter Done!

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  8. ssouci

    ssouci Well-Known Member

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    why would I need these?... I don't remember ever having to do so, including about 25 years ago when I had another 2230... ???... ie., what is the causing the problem (the the shorting plug is able to fix) and is there another way to fix this?
     
  9. avionic

    avionic " Black Knights " Subscriber

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    Hook up a turntable..
     

     

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  10. ssouci

    ssouci Well-Known Member

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    I'm referring to C713 which is a "big" single electrolytic in the middle of that phono board... I bumped up to 220uF from 100uF using Panasonic FM... not sure if that has any bearing here with my hum issue, but that increase was to "help improve local filtering" (as per Tom)
     
  11. bktheking

    bktheking Gitter Done!

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  12. ssouci

    ssouci Well-Known Member

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    yes, I did put in the double diode and replaced the other diodes as well... basically, I followed Catrafter's suggestions for this phono board, including the bump up to 220uF (which again may have nothing to do with this)... I belive the polarity is correct on that central cap as I coiped what was there (and probably looked at the PCB markings as well)
     

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    Last edited: Nov 18, 2012
  13. catrafter

    catrafter Marantz Specialist Subscriber

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    Maybe a broken ground somewhere? J702, J707 or even on the rear panel RCA jacks.

    Tom
     
  14. patfont

    patfont AK Subscriber Subscriber

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    with the volume set on low and selector to phono gently wiggle the phono RCA inputs, and see if this insites that hum, make sure volume is low, just in case.
     
  15. ssouci

    ssouci Well-Known Member

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    MAJOR DISCOVERY !!! ... just spent an hour checking all the grounds related to the phono board, plus the ground beside the RCA outputs... cleaned all the surfaces and even lightly sanded them then applied Dexoit Gold 100%, then reseated snugly... none of it made any real dfference... reversing the power plug made a very tiny improvement

    then I started playing with the power bar... defeated the ground, plugged my 2230 directly into the wall (instead of the power bar), etc., nothing really helped... then I started unplugging each item in my power bar (APC brand) one by one to see if any difference... unplugging some items made only a very slight difference until I came to the plug for my 2275 Marantz... upon unplugging it, the hum problem disappeared completely!!!... my 2230 ran in Phono (no turntable connected) with zero hum, although I did start hearing some smooth hissing at 3/4 volume (which would be pretty cranked, so I suppose acceptable?)

    ?????... and that's with the 2275 turned off... in fact, turning it *on* reduced the problem (and introduced a new slight different buzzing sound)

    I should note that my 2230 is sitting directly on top on my 2275, and regular Maramtz feet and a layer of cardboard... also, the bottom panel of the 2230 is still off... also, I plug everything into the power bar, incl. my TV, PVR, lamp, etc.

    is this weird or what?... any ideas of what is going on, why, and what I should do (other than simply unplugging the 2275 when not being used)?

    thx!
     
  16. bktheking

    bktheking Gitter Done!

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    are you sure it's not the power bar itself?
     
  17. ssouci

    ssouci Well-Known Member

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    at this point I don't think so...

    both my 2230 and 2275 are plugged into the same power bar (along with a bunch of other stuff)...

    I must empahsize that the 2275 is turned OFF, however is somehow causing noise/hum in the 2230!...

    I tried plugging the 2230 into the wall outlet (shared with the power bar's main plug), however the 2230 was still picking up the noise the same way... somehow it seems it's picking up noise from a turned-off 2275 by just being near it???... how can this be possible?

    I should note that when I was setting idle current etc. and had moved my 2230 off of the 2275 and onto the floor nearby, the phono hum/intereference was still there, but quite a bit reduced... so proximity to the 2275 seems to be a factor
     
    Last edited: Nov 19, 2012

     

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  18. catrafter

    catrafter Marantz Specialist Subscriber

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    Installing the bottom cover on the 2230 may help.

    Tom
     
  19. ssouci

    ssouci Well-Known Member

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    I will be trying that soon, however I'm still very surprised that the 2230 is picking up something from the 2275 from within my wiring and/or physical setup... is that even electrically possible -- considering that the 2275 is turned off?
     
    Last edited: Nov 19, 2012
  20. ssouci

    ssouci Well-Known Member

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    OK FIXED !!!!!!!!!!!!!!!

    :thmbsp::thmbsp::thmbsp::thmbsp:

    I was trying some experiments and found that the hum quickly disappeared when I lifted it off of my (unplugged) 2275... definitely a proximity thing with a quick drop off (after approx 6")

    then, when I placed the 2230 on the carpeted floor of my room instead, the hum came back but not as strongly as ontop of the 2275... same thing anywhere in the room and wherever I plugged the unit in

    so, I replaced the bottom cover (first time since rebuild), and presto -- no more hum, even on top of the 2275!... thanks Tom!

    now, it is all quiet even at max volume for aux, tape

    however, for phono, I get a modest hiss starting at 1/2 volume postion, increases more noticeably at 3/4 and further to 100% volume.... it's a smooth even hiss, no 60Hz hum at all

    Q: is this normal and what might causing it? (probably could not be heard over any music I suppose, especially at 1/2 volume or higher.... maybe nothing to be concerned about?)

    note I fully recappped the phono board, plus replaced the transistors, plus added in the special double-diode mod

    ???

    thx!
     
    Last edited: Nov 19, 2012

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