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Thorens TD-150 hum [message #13182]

Thu, 30 November 2006 21:23

shoeihell
Messages: 7
Registered: May 2009

Esquire

I've have had this turntable since '73. It was not being used much and so recently I went through and replaced the 'hair' tonearm wires with the correct gauge and color...what a crummy job. Then I replaced the RCA cables with new. All of this improved the sound quite a bit. What I have now is hum. I can turn the gain all the way up on my receiver and there is almost no hum. But....turn on the platter and there is significant hum. I don't remember this ever being a problem before and I can't really blame the cart, because it's only when the turntable motor runs. I tried to ground the motor itself but that only increased the hum. The ground I have now comes from the two cart shielded grounds and goes to the grounding lug on the receiver. I'm wondering if it's the motor itself, something to lube or some cap gone bad related to the motor? Maybe somebody had had this same problem with this series turntable?

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Anybody, please? [message #13184 is a reply to message #13182]

Sun, 03 December 2006 19:36

shoeihell
Messages: 7
Registered: May 2009

Esquire

Would appreciate some feedback....

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Ground or bad connection [message #13188 is a reply to message #13184]

Tue, 05 December 2006 09:04

Wayne Parham
Messages: 18783
Registered: January 2001

Illuminati (33rd Degree)

The symptom of hum on motor run is a pretty good clue. Sounds to me like when you re-wired, you lifted the ground connection or possibly made a bad connection to the cartridge outputs.

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Re: Ground or bad connection [message #13189 is a reply to message #13188]

Tue, 05 December 2006 09:47

shoeihell
Messages: 7
Registered: May 2009

Esquire

Thanks for a reply Wayne, I was beginning to wonder if there was life out there.;-) I'm not sure I understand what you mean by "lifted the ground connection"? Everything is soldered like before....I even checked to make sure nothing it touching inappropriately. If it were the leads at the cartridge output as you suggested, wouldn't there be substantial hum when the receiver gain was turned all the way up and the motor not running? At the socket where the cart plugs in are the four soldered connections that start their runs down the arm-each of these connections have a little plastic sleeve to cover them. The hum is very background, but noticeable and only when the motor is turned on.

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Re: Ground or bad connection [message #13190 is a reply to message #13189]

Tue, 05 December 2006 15:00

Wayne Parham
Messages: 18783
Registered: January 2001

Illuminati (33rd Degree)

When I say, "lifted the ground connection," I mean that it was probably made open or nearly open. If the ground connection is soldered to a spade lug that is tightened to the chassis with a screw, make sure the mechanical connection between lug and chassis is clean. Something has probably made the ground connection less effective. Check also to see that your signal wires are not run near the motor or power lines.

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Re: Thorens TD-150 hum [message #13191 is a reply to message #13182]

Tue, 05 December 2006 18:42

colinhester
Messages: 1349
Registered: May 2009
Location: NE Arkansas

Illuminati (3rd Degree)

Does the hum get louder if the arm is moved towards the center of the platter?

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Re: Thorens TD-150 hum [message #13192 is a reply to message #13191]

Tue, 05 December 2006 20:28

shoeihell
Messages: 7
Registered: May 2009

Esquire

Ever so slightly as the platter is turning-no difference with the platter off. And this is with the gain turned ALL the way up. I do get a substantial increase in noise however, when I take my hand and move it close to the cart and then less as I back my hand away.

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Re: Ground or bad connection [message #13193 is a reply to message #13190]

Tue, 05 December 2006 20:36

shoeihell
Messages: 7
Registered: May 2009

Esquire

That's what I thought you meant and there is a soldered spade lug screwed to the chassis. I don't think I checked that end, but did the other as it was attached to the tonearm metal pivot bracket, which I had to disassemble for the new tonearm leads. That's a good idea on the 'hair' wires, but I think the power mains go out the other side and so the tonearm wires are only near the RCA cable. I do have the ground going out right against the power mains on its way to the receiver-will that make any difference? The ground is also pretty small...like 20ga.

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Re: Ground or bad connection [message #13195 is a reply to message #13193]

Wed, 06 December 2006 19:30

Bill Agee
Messages: 17
Registered: May 2009

Chancellor

Where exactly does that ground wire connect to the tonearm? It may be that it has come loose fron the arm.

Try this: Remove the tonearm ground connection from the chassis where it is connected with the screw. How has the noise changed now?

Use another piece of wire, just for a test, and temporarily connect it from the tonearm to the chassis. How has the noise changed now?

Bill

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Re: Ground or bad connection [message #13198 is a reply to message #13195]

Thu, 07 December 2006 20:52

shoeihell
Messages: 7
Registered: May 2009

Esquire

OK, there is the base of the tonearm tube...(where the tube is screwed to the part that pivots, like a 'base'). There is a spade there that is attached to the pivot base, goes into the tonearm tube and then down the vertical shaft with the tonearm wires, comes out and is screwed to the metal table base with another spade/screw. The other ground goes from the terminal board of the cart shielded leads/RCA shielded leads to the receiver lug ground, via a 20ga solid core wire-that's easy enough to change to another type of wire if deemed too small or wrong type.

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