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Gnd Hum B & O Beogram 3404

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Gnd Hum B & O Beogram 3404

Postby jmccanna » 10 Jan 2017 01:26

Hi,

My recently purchased 3404 has developed a ground hum. I am using a DIN to RCA converter purchased off of Ebay that said it worked for this TT. (I know I know). Anyway, it does work but there is a persistent hum. I did research and have soldered a bare wire to the sleeve of the DIN and connected it to the ground on my amplifier. The hum is still there. I took the bottom off and there is a small black wire that is hanging in the air that under a mag glass looks broken and there is a solder joint near it that clearly used to have a wire soldered to it. Here is a pic:

http://imgur.com/mSdHmFo

I soldered it onto the broken link and the hum is worse.

I have downloaded the manual and will study it next. Thoughts?

Thanks,

James
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Re: Gnd Hum B & O Beogram 3404

Postby Copperhead » 10 Jan 2017 03:46

jmccanna wrote:Hi,

My recently purchased 3404 has developed a ground hum. I am using a DIN to RCA converter purchased off of Ebay that said it worked for this TT. (I know I know). Anyway, it does work but there is a persistent hum. I did research and have soldered a bare wire to the sleeve of the DIN and connected it to the ground on my amplifier. The hum is still there. I took the bottom off and there is a small black wire that is hanging in the air that under a mag glass looks broken and there is a solder joint near it that clearly used to have a wire soldered to it. Here is a pic:

http://imgur.com/mSdHmFo

I soldered it onto the broken link and the hum is worse.

I have downloaded the manual and will study it next. Thoughts?

Thanks,
James


Did you ever plug the DIN directly into an amp or is this the first time you have actually plugged the deck in? DIN plugs of that age can cause a hum due to wires breaking off, seeing as you are able to solder, I suggest you buy a pair of RCA plugs and bin the DIN. I am assuming your amp only has RCA inputs anyway.

Not sure about the configuration of your cable, on earlier models an earth wire could attach to the shield (on RCA configuration) and that would go to the grounding post.

Might be that the DIN is no longer earthed, attaching a wire to that would be of no use.

I can't see the tonearm wires properly in the photo, but hopefully no one is messed around with them. The black wire should be attached to the post with a large blob of solder, I think. Fit some RCAs to the cable and re-attach the black wire.

The service manual will show you where the wire attaches anyway. Again, don't trust the DIN if it's the original one. They were cack.

Good luck.
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Re: Gnd Hum B & O Beogram 3404

Postby jmccanna » 10 Jan 2017 04:12

Copperhead,

Many thanks. I had actually reached the same conclusion. After I posted I tried a couple of different ways to ground the DIN and a different amp with a phono it while there was minor improvement it was not enough.

It is the original DIN and I was wondering why I was bothering - thinking about resale at some point I guess - which I am highly unlikely to do anyway. I will cut it off and wire in an RCA directly.

I have reattached the black wire underneath already after putting a magnifying glass on it and the post. It was clear to me that it was formerly attached to the post there. Not sure what it does until I study the schematic. I am hopeful about this.

Thanks again from the Pacific NW.

It sounds good given its age.
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Re: Gnd Hum B & O Beogram 3404

Postby jmccanna » 10 Jan 2017 04:16

Quick question: In the picture, the black wire is broken off at the end but is soldered to a screw before that. Would that screw be the earth ground for the TT?
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Re: Gnd Hum B & O Beogram 3404

Postby jmccanna » 10 Jan 2017 21:22

Hi,

Well, I took it apart and tested continuity from the DIN to bottom of the TT. My left channel was hinky as was the earth wire. Surgery ensued - I cut off the DIN connector and retested continuity. All was good then. So, I soldered in new RCA connectors and an earth wire. Shrink tubing to protect the connections. All connected to my amp now as should be and it sounds great. One other thing I did was to take off the cartridge and spray just a little DeOxit in and then carefully wiped it with a small bit of paper towel and let it dry for half an hour while I did the soldering.

Sounds great and thanks for the tip on the DIN.

Have a good day!

Thanks,

James
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Re: Gnd Hum B & O Beogram 3404

Postby Copperhead » 10 Jan 2017 22:03

jmccanna wrote:Hi,

Well, I took it apart and tested continuity from the DIN to bottom of the TT. My left channel was hinky as was the earth wire. Surgery ensued - I cut off the DIN connector and retested continuity. All was good then. So, I soldered in new RCA connectors and an earth wire. Shrink tubing to protect the connections. All connected to my amp now as should be and it sounds great. One other thing I did was to take off the cartridge and spray just a little DeOxit in and then carefully wiped it with a small bit of paper towel and let it dry for half an hour while I did the soldering.

Sounds great and thanks for the tip on the DIN.

Have a good day!

Thanks,

James


Well done, James. When you get a bit more familiar with the turntable give it a service.
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Re: Gnd Hum B & O Beogram 3404

Postby jmccanna » 10 Jan 2017 22:14

Hello,

I will do that. Can you describe what you mean though? I am fairly adept at figuring things out and can replace parts and such. Your comment sounds more like maintenance and I would curious as to what you recommend?

Thanks,

James
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Re: Gnd Hum B & O Beogram 3404

Postby Copperhead » 11 Jan 2017 04:16

jmccanna wrote:Hello,

I will do that. Can you describe what you mean though? I am fairly adept at figuring things out and can replace parts and such. Your comment sounds more like maintenance and I would curious as to what you recommend?

Thanks,

James


James, if the motor can be stripped, and you are confident doing so, start there.
Platter bearing will also need cleaning and re-lubing.
If you have the service manual at hand, work from there.

I actually have one of these decks, took the cartridge and belt off and lost them both. It now sits in the spare room, somewhere hidden from my view.

Whatever you do, make sure to make a record of what you take off and exactly where everything goes. Even simple things will become difficult to work out once you start reassembly. And keep the cartridge well away from the arm during the servicing, last thing you need is to be buying another one.
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Re: Gnd Hum B & O Beogram 3404

Postby jmccanna » 11 Jan 2017 22:33

I am not too keen on messing with the motor but coud see lubing the bearings. It does have a little bit of rumble. The belt is in good shape and it runs smoothly. Thanks.
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Re: Gnd Hum B & O Beogram 3404

Postby Copperhead » 12 Jan 2017 00:52

jmccanna wrote:I am not too keen on messing with the motor but coud see lubing the bearings. It does have a little bit of rumble. The belt is in good shape and it runs smoothly. Thanks.


Fair enough, then just put a couple of drops of thin oil on the top bearing. Let the oil couple run on the shaft and into the bushing.

Hopefully it will get rid of the rumble.

I can't remember what the belt looks like, but on some B&O machines the replacement belts carry a lot of vibrations from the motor. The original ones were much softer and quieter.

Can you hear noise from the motor with the belt off?
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Re: Gnd Hum B & O Beogram 3404

Postby jmccanna » 12 Jan 2017 01:07

Hi,

I have not tried it with the belt off. To my knowledge, this is all original parts. Not sure though.

I will try that when I get back from a trip.

Take care.

James
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