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Repair / Help Forum => Repair / Help => Topic started by: non-prophet on December 04, 2011, 04:57:13 PM

Title: Phono hum
Post by: non-prophet on December 04, 2011, 04:57:13 PM

Ok, this might be a simple problem but I have never run across it.  I hooked up my turntable, finally, and it has a hum regardless of it being used, turntable off and phono on in the preamp.  I touch the tonearm and the hum gets amplified.  I checked the pre with another table and no problems.  I would guess this is a grounding problem, I checked the connections and did not see any problems.  Any help will be appreciated.  Here is the set up:

Melos GK-1 tube pre, tube phono
Fairchild 412 turntable
Melos CDP CD player
Melos CDT Tube buffer
Acurus A-200 amp
Adcom ACE-515 Power conditioner
Apogee Centaur Minor, hybrid ribbon speakers

Title: Re: Phono hum
Post by: SunnyDaze on December 04, 2011, 07:18:15 PM

What is it setting on?

The only time I've ever had this issue, I had the TT sitting on an 18" x 18" concrete slab. It turns out, the center wasn't yet totally dry. It was somehow inducing a field that was significant enough to cause the 60hz "hum".

Weird, huh?

PS - Nick, call me. I need to send you cash.

Title: Re: Phono hum
Post by: Slim-Shaddy on December 04, 2011, 09:21:24 PM

Recheck the wires to your cart. Then try a different cart. neither work? Go to the arm wires

Title: Re: Phono hum
Post by: Anders on December 04, 2011, 10:35:49 PM

If hum gets louder when you touch the arm then the arm isn't grounded.
Somewhere the separate ground wire is broken.

Anders

Title: Re: Phono hum
Post by: OldiesButGoodies on December 05, 2011, 07:20:12 PM

Per Anders,  can you check continuity between the ground wire and the chassis,  arm assembly, etc to see if you find a break?