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Thorens TD-124: Help me solve my hum problem

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Posted on November 7, 2009 at 06:24:20
Jim Austin
Reviewer

Posts: 491
Location: Northern New England
Joined: November 8, 2007
 Hi folks. My Thorens, which I've been using for quite a long time, has developed a new hum (through the speakers) and I'm having trouble diagnosing it. (Previously I had a hum that was due to tonearm grounding, but this is something different.)

The hum comes and goes almost at random. The hum can start for no apparent reason (I first noticed it when my son lifted the tonearm last weekend). Sometimes I can make it go away by cycling the power off and on. BUT SOMETIMES THE HUM REMAINS, EVEN WITH THE POWER SWITCHED COMPLETELY OFF! Sometimes cycling it works, sometimes it doesn't. So, while it seems to involve the switch, but it doesn't seem to involve the motor, or at least not directly. And sometimes it will come back again, even if I don't touch the switch again. And sometimes cycling the power has no effect...which is to say, I have to do it two or three times to get rid of the hum.

So the power switch is involved, but I really can't see how. I'm most mystified by the fact that, though it involves the switch, it can occur even with the power to the motor off.

Anyone else experienced this? What was your solution?

Thanks,
Jim
http://www.jazz-etc.com
RE: Thorens TD-124: Help me solve my hum problem, posted on November 7, 2009 at 13:50:48
MAS
Audiophile

Posts: 2073
Joined: February 26, 2002
 Once you have the hum, you could verify it is from the power by unplugging the power cord rather than just turning it on/off with the switch. As you know, there is still power being supplied to the TT up to the switch. It would be ideal to have the TT plugged in to a switched receptacle or power bar so you could turn it off without even disturbing the power cord. Of course, the rest of the system has to be on to see if the hum is still there.

Most of the time I have had hum, it was because of tonearm wiring issues. Make sure everything is clean with a solid contact.
RE: Thorens TD-124: Help me solve my hum problem, posted on November 7, 2009 at 12:48:38
amandarae
Audiophile

Posts: 1323
Location: So.Cal
Joined: November 30, 2004
 Hello Jim,

I do not know if the "anti pop" capacitors can do that but maybe you can try this.

As you know, most TD 124's (MKI and MKII) version comes with two prong power cable (main power), while our amps (pre, power, phono pre) most of the time are three prongs variety. I was thinking that the hum is coming from the chassis as it lacks ground connection compared to the other equipment in the system.

Underneath the arm board skeletal frame, in the middle brace, is a screw hole that serves as a grounding point for the chassis. You can try connecting a screw there with a wire with, the wire's other end to your linestage or phono preamp main ground point or if it is possible, to a grounding point/tab of the receptacle where you get the power for the table. regards,

Abe
DIY, all the time!
RE: Thorens TD-124: Help me solve my hum problem, posted on November 7, 2009 at 08:24:44
johnsonad
Audiophile

Posts: 265
Location: San Diego
Joined: June 9, 2008
Contributor
  Since: September 27, 2009
 Jim, it is probably in the tonearm ground, not the table. Mine does the same thing from time to time but I can lift the ground on my arm. You may want to clean up the ground contacts on the motor mount and trace out how your tonearm is grounded. Try also using an alligator clip from your tonearm to the table chassis and see if this resolves it (metal to metal). More than likely it is an easy fix.

Regards,

Aaron

RE: Thorens TD-124: Help me solve my hum problem, posted on November 7, 2009 at 06:39:23
Daveslater
Audiophile

Posts: 470
Location: UK
Joined: June 11, 2003
 There is an anti pop capacitor across the power switch. Could be this failing.
Best of luck

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