Humming Dual CS 505-01

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ReMC
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Humming Dual CS 505-01

Post by ReMC » 04 Dec 2019 12:37

Hello people,

First ever post here :-) Simple question, bought myself a used CS 505-01 in brilliant condition, for my second system. It has the orginal Dual TKS49s cartridge in it along with the Dual DN 149s needle. However, when I plug the unit into my Project Phonobox, all I get is no music but I do get strong humming. The earth lead of the unit is connected to the earth connection of my Project. I did get some very very weak music sometimes at higher volumes but the humming is by far dominant. The needle seems to be ok. I can hear the music perfectly fine with my ear above the record.

Any idea what could be the issue? Thanks. BR. Remco.

mrBoj
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Re: Humming Dual CS 505-01

Post by mrBoj » 04 Dec 2019 13:35

Try to clean the connection between the cartridge and arm wires. They may have been oxidized.

ReMC
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Re: Humming Dual CS 505-01

Post by ReMC » 04 Dec 2019 14:44

Thanks, but how do I do this? Is a cotton tip with some alcohol the proper way of doing this? And where do I need to clean exactly? Do you mean the various little connectors attached to the various coloured thin wires?. Thanks

mrBoj
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Re: Humming Dual CS 505-01

Post by mrBoj » 04 Dec 2019 20:44

I don't think u can do much with alcohol, especially if the connectors are golded. Try soft brush and toothpaste then clean with alcohol. There is also some antioxidant spray, and a glass pencil for cleaning, but toothpaste is cheaper and it works just fine. And, yes, connectors attached to the various coloured thin wires. There are plugs and pins. If they were dark, they are oxidized. Be careful! Pins can be soft and can easily band. Don't forget where each coloured wire goes ;-) . take a picture before ;-)

ReMC
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Re: Humming Dual CS 505-01

Post by ReMC » 05 Dec 2019 10:41

Thanks a lot. Will try and let you know. Also noticed the humming is greatly influenced when moving the RCA plugs of the Dual once connected to the Project Phonobox. Could the humming be caused by bad RCA cables/plugs?

Legrace
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Re: Humming Dual CS 505-01

Post by Legrace » 05 Dec 2019 12:40

ReMC wrote:
05 Dec 2019 10:41
Thanks a lot. Will try and let you know. Also noticed the humming is greatly influenced when moving the RCA plugs of the Dual once connected to the Project Phonobox. Could the humming be caused by bad RCA cables/plugs?
Most definitely.

ReMC
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Re: Humming Dual CS 505-01

Post by ReMC » 05 Dec 2019 13:33

Thanks. Had a feeling already. Will try the cleaning first, followed by a check of the phono preamp (just to be sure) before replacing the current RCA plugs. If that doesn't work, the cables need to be replaced as well, something I cannot do myself. Thanks.

Hugues TR4
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Re: Humming Dual CS 505-01

Post by Hugues TR4 » 05 Dec 2019 20:22

Another good way of cleaning the oxydized silver coated contacts is rubbing with some silver cleaning product (Silvo, Hagerty's or similar) on a q-tip and get them shine like your grand mom's silver teapot.
Once they shine, rub them with the clean side of your q-tip to wipe out the product.
The small clips on the cart could be cleaned with some Deoxit on one of these small brushes used by dentists to clean between the teeth.
Hope this helps,
Cheers,

Hugh

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Re: Humming Dual CS 505-01

Post by sotpal » 05 Dec 2019 22:15

I'd say 90% faulty RCA cables. I had to replace them on all of my "used" vintage Dual turntables when I got them (while everything else was in very good condition).

But before replacing those, check the ground cable for continuity first if you have a multimeter.
Just remove the small screw on the headshell, then remove the cartridge by pushing the lever of the headshell to the back, then if you look closely under the headshell you will find a black wire soldered there.
Just put one multimeter probe on that one and the the other probe to the other end of the ground wire (the one that goes to your Phonobox.
(that will give you access to the headshell contacts as well so you can check their condition too..)

An alternate location to check the continuity (if you don't want to mess with the headshell) could be the screw of the rear part of the headshell (it's underside where the headshell meets the tonearm),
BUT i would prefer to test the absolute end of the ground wire which is at the headshell itself.

If the multimeter beeps then the ground cable is ok.

ReMC
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Re: Humming Dual CS 505-01

Post by ReMC » 06 Dec 2019 11:03

Thanks for all the replies people, very much appreciated. Had an interesting evening yesterday and morning today. Bought some contact cleaner and used it on all visible contacts and even on the contacts inside the headshell. No effect. Same old humming again. Used both earthed and unearth wallsockets. No effect. Checked the RCA cables for cracks, damage etc. Nothing to be seen. Earth wire is in tact. Phono preamp is OK. Excanged cables from/to phono-/ pre-/poweramp. No effect. Also tried an old Garrard SP25mk1 I bought for 20Euro's a month ago. Less humming but distorted weak sound. I think that needle is gone. Finally I tried something I avoided doing and that is to physically remove the little wires/clambs on the cartridge. (I am 2 meters tall with huge hands, not something I look forward to or like doing) I just removed, re-plugged, unplugged and re-plugged all the wires. That worked!! Finally I have some music. There is still some slight hum in the background when I raise the volume with the needle up and the table spinning but I think this is your avarage noise. Now that it seems to be in the cartridge wires, I can perhaps think about putting an adapter plate in place and buy a better catridge instead. By the way, this Dual system for replacing or removing the cartridge is a real pain.

ReMC
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Re: Humming Dual CS 505-01

Post by ReMC » 06 Dec 2019 12:20

Oh, before I forget, I also noticed that the little pin that is connected to the little blue wire was out of place. (compared to the other ones). I carefully adjusted this with little force. Just checked, this is the earth lead. Maybe the previous owner damaged the wiring slightly? Anyway, almost happy now. Trying to get that last bit of hum out of the way. The deck itself is really in incredible shape :-) Paid just 50 Euro's for it :D

Minstrel SE
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Re: Humming Dual CS 505-01

Post by Minstrel SE » 09 Dec 2019 06:52

Hi
I haven't read the other replies but from my extensive experience its almost certainly the Phono plugs which fail on many units. Horrible moulded phono plugs and a pet hate of mine

When they often fail they introduce a mild to a very loud earth short style humming/buzzing that could damage your system

I cut them off and replace with Neutrik Rean phono plugs...job done.

Its 90%+ that problem...its easier to keep the original leads and solder some better quality phono plugs on.....something I dont hesitate to say Dual should have done in the first place :)

One other alternative is rumble hum cause by an old dry motor and other drive systems out of tolerance now...its all a process of elimination

All the best with it

lapratho
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Re: Humming Dual CS 505-01

Post by lapratho » 09 Dec 2019 07:48

I don't remember, if the 505 has a ground shorting switch for the audio, but that is a standard thing with most older Dual TTs. Sometimes it hangs in the closed position, so audio is shorted to ground not just in the OFF position for the motor, but also when playing. A bypass can solve that problem, but is of course for us, who want original restorations a "dirty" trick.
Rebuilding the arm for a 1/2 inch headshell is a better option than the wonky adapter plates. Tried that, didn't sound right. You will also need a heavier counterweight or add-on weight, which can be hard and expensive to come by.

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