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 Post subject: Tonearm hum
PostPosted: Thu Dec 21, 2017 2:30 am 
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Joined: Mon Apr 17, 2017 5:26 am
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Location: Vancouver, BC, CA
Hey all,

Me again. I recently bought a used RB250 arm with an older TFA rewire, and I think the arm is giving me an audible electrical hum. Any advice about where the problem might be?

A few things I notice:

- The volume of the hum increases if I touch the tonearm anywhere.

- The volume of the hum increases if I touch the red or white wires that connect to the cartridge (nothing happens with green or blue).

- The volume of the hum increases if I touch the tonearm cables near the preamp, where the two cables meet and enter their common housing.

- The volume of the hum decreases if I touch the metal area on the bottom of the cartridge (currently an AT95e).

- The volume of the hum decreases if I touch both RCA connectors at the same time where they connect at the preamp.

Since my preamp has a headphone out, I am able to test without using my amp. The buzz is present at the preamp whenever the tonearm cables are plugged in. If I unplug them, the preamp is quiet. Connecting/disconnecting the RCA cables that lead out of the preamp to my integrated amp makes no difference. Preamp is an ART USB Phono Plus.


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 Post subject: Re: Tonearm hum
PostPosted: Thu Dec 21, 2017 3:02 am 
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Joined: Wed Mar 12, 2014 5:47 am
Posts: 69
Location: Toronto, ON, CA
Is there a good ground wire connection between the turntable and the preamp?

Hopefully others will chime in.


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 Post subject: Re: Tonearm hum
PostPosted: Thu Dec 21, 2017 3:07 am 
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Joined: Mon Oct 17, 2011 6:55 pm
Posts: 2805
Location: Toronto, ON, CA
Sounds like you may have a bad ground. You can verify this by taking a piece of wire, stripped at both ends – attach the wire to the ground post of your phono pre. And with the other end, fixing (or touching) to something metallic on the arm, preferably something that is not anodized like the arm shaft that attaches to the base of the table.

But I’d contact Gene at TFA.


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 Post subject: Re: Tonearm hum
PostPosted: Thu Dec 21, 2017 3:39 am 
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Joined: Sun Nov 28, 2010 5:56 pm
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Location: Milton, ON, CA
Definitely bad ground. Check the clips that attach to the cartridge or the other end. Usually the break is at the solder joints at the end


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 Post subject: Re: Tonearm hum
PostPosted: Thu Dec 21, 2017 4:24 am 
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Joined: Sun May 28, 2017 1:25 pm
Posts: 351
Location: Toronto, ON, CA
Also possible bad RCA's.At least one of them.But it could be a break in the internal cable inside the arm (hopefully not).Sometimes a cartridge can have a ground issue as well, assuming you have a cartridge installed.


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 Post subject: Re: Tonearm hum
PostPosted: Thu Dec 21, 2017 4:35 am 
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Joined: Sat Mar 14, 2009 5:22 pm
Posts: 111
Location: GTA, ON, CA
Use a continuity tester to check if the Tonearm tube is grounded to the ground wire. If not then it’s a loose ground lead on the arm tube. Usually happens on Rewired rega arms because the ground lead is usually cnnected by friction fit.

Yes touching the tiny red and white wire wil cause huge hum while touching the green/blue wires will not. That’s normal.


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 Post subject: Re: Tonearm hum
PostPosted: Thu Dec 21, 2017 5:33 am 
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Joined: Thu Jan 13, 2011 11:29 am
Posts: 639
Location: St.Catharines, ON, CA
Check headshell end first.Make sure you're getting good contact.

What table?

Gary


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 Post subject: Re: Tonearm hum
PostPosted: Thu Dec 21, 2017 7:46 am 
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Posts: 193
Location: Vancouver, BC, CA
Thanks all, I'll try a few of these things & report back.

I got in touch with Gene yesterday, too, and he also suggests that the ground has probably come disconnected internally.

Table is an older Rega Planar 2 w/ teak surround. The hum happens whether the table motor is plugged in or not.


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 Post subject: Re: Tonearm hum
PostPosted: Thu Dec 21, 2017 9:48 am 
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Joined: Mon Apr 05, 2010 6:12 pm
Posts: 583
Location: Toronto, ON, CA
several possible issues
bad cables with no shielding in them will give that hum. recabling should solve that issue

bad internal grounding, wiring through tone arm
also cables to headshell
headshell itself and or cartridge

try a different headshell and swap out the cartridge

whether the tt is plugged in or not makes no difference
2 different boards with connection to each other


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 Post subject: Re: Tonearm hum
PostPosted: Thu Dec 21, 2017 10:29 am 
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Location: Vancouver, BC, CA
Well, having taken it apart, I can see that the ground wire has definitely come disconnected. It's also pretty clear that this is not a professional job, and Gene confirms it was not TFA's work. Not sure where/how that mistake was made yet; will have to follow up with the seller.

NB, for those who are interested, the ground wire in this arm seems to have been connected to a point just behind the pivot, rather than with friction fit at the front as shown above.

Time to figure out next steps, I guess. I suppose I could source a new ground wire and try to fiddle with a fix, but I'm not sure it's worthwhile... maybe better to just start fresh. Rats.

I'm learning a lot, but so far I've only managed to listen to maybe 6-8 hours of music on vinyl since I started down the turntable path in early November. Gets a bit discouraging. I have a lot of respect for you folks who've been working with TTs forever. You are patient folk.


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 Post subject: Re: Tonearm hum
PostPosted: Thu Dec 21, 2017 10:53 am 
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Location: Vancouver, BC, CA
two2the8 wrote:
Well, having taken it apart, I can see that the ground wire has definitely come disconnected. It's also pretty clear that this is not a professional job, and Gene confirms it was not TFA's work. Not sure where/how that mistake was made yet; will have to follow up with the seller.


FYI, having checked our correspondence, I can see that the seller was clear that the tonearm had been "rewired with TFA wire." My mistake completely for conflating this with there having been a TFA rewire. It's DIY work (and it looks pretty good to me).

Anyway, next steps. Trying to rig up a temporary fix while I source another groundwire. Maybe I'll just take it to a shop; probably it's time to admit that I'm out of my depth.


Last edited by two2the8 on Fri Jan 12, 2018 11:55 am, edited 1 time in total.

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 Post subject: Re: Tonearm hum
PostPosted: Thu Dec 21, 2017 2:13 pm 
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Location: Toronto, ON, CA
two2the8 wrote:
two2the8 wrote:
Well, having taken it apart, I can see that the ground wire has definitely come disconnected. It's also pretty clear that this is not a professional job, and Gene confirms it was not TFA's work. Not sure where/how that mistake was made yet; will have to follow up with the seller.


FYI, having checked our correspondence, I can see that the seller was clear that the tonearm had been "rewired with TFA wire." My mistake for conflating this with there having been a TFA rewire. It's DIY work.

Anyway, next steps. Trying to rig up a temporary fix while I source another groundwire. Maybe I'll just take it to a shop; probably it's time to admit that I'm out of my depth.



glad you found the problem...don't go crazy for a ground wire, any 24g will do fine
(I've rewired well over 100+ turntables)


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 Post subject: Re: Tonearm hum
PostPosted: Thu Dec 21, 2017 2:34 pm 
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Location: Vancouver, BC, CA
warhorse wrote:
glad you found the problem...don't go crazy for a ground wire, any 24g will do fine
(I've rewired well over 100+ turntables)


That's helpful to hear. The thing is, this arm was grounded just behind the pivot, so there's very little wire in there to work with. It's also a pretty finicky place to try and get to. If I'm careful, maybe I can manage to put it back where it was, but it seems reasonably likely that I'll break or burn something else in the process.


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 Post subject: Re: Tonearm hum
PostPosted: Thu Dec 21, 2017 3:33 pm 
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Location: Toronto, ON, CA
that wire will be a 32AWG braided...tread carefully
your best bet is do pull a new wire


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 Post subject: Re: Tonearm hum
PostPosted: Fri Dec 22, 2017 1:52 pm 
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Location: Vancouver, BC, CA
warhorse wrote:
your best bet is do pull a new wire


Hmm, thinking about this a bit... could I friction-fit the groundwire at both ends? I know many do it at the headshell end, and that seems OK. Could I also pull the groundwire through the nut at the pivot, and use a friction-fit it at the base of the tonearm? If so, maybe I could fix the problem without having to solder anything.

Though as I write it out, I realize it's pretty hack-y. Probably better just to take it in for service.


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