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Ariston Audio RD11s : electrical hum when off

davstev

davstev

Well-Known Member
I picked up this rather nice RD11s recently with a Mayware arm and Audio Technica at13ea cartridge. I am lovingly restoring it, although it came in decent condition overall and just needs a bit of TLC and to set up the arm (which is a bit of work).

It's all going well, but last night I powered the big orange power switch off, but continued to hear a very very faint electrical hum. So faint that I wasn't sure if it was for real at first. Putting my ear up to the plinth beside where the motor is, is where this hum comes from. And the hum goes away after I unplug the power cord from the wall outlet.

Confused as to why a hum can be heard after the power switch is turned off. Reminder that the orange power switch on this table actually serves to turn the motor on and thus turn the platter too, so it's kind of a one-switch-does-all type thing.

Why would I be hearing a very faint hum when it's turned off? Is this normal?

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The motor probably always has power going to it Like in the AR XA/XB turntables.

Remove the outer platter and see if you feel the pulley vibrating, that will confirm power still at the motor. it haw the did it back then.

Athanasios
 
So, with my fingers on the motor spindle, when plugged into the wall but not turned on via the on/off switch, I feel a bit of a resistance & minor vibration when I turn the motor spindle with my finger.

As soon as I unplug it, turning the spindle by hand is perfectly smooth. That tells me that there's some electrification going to the motor when it's plugged into the wall regardless of if the power switch is turned on.

Is this a problem? It seems odd that there's electricity going tot he motor 24/7 and 365 days a year. However, I suppose it's by design, so it can't be that bad?

Are a lot of turntables like this? I seem to recall the Thorens TD-160 having the same manual feel to the motor spindle when turned.
 
ripblade said:
Are you sure the switch is operating on the hot side of the AC power, not the neutral?
Click to expand...
I am not sure how to respond to this, becasue I don't think I really understand the question! But I have poked around inside the table and it doesn't seem to have been modded so I think it's the original design for the RD11s.
 
If you look at the diagram in the VE thread you posted you'll see that the phase cap (.25mfd, supplied with motor) is on the neutral (white) wire, with the switch on the hot (yellow/black) wire. If this is inadvertently reversed the cap will be 'live' instead, as will be the motor, resulting in the hum and vibration.

Try reversing the plug at the wall outlet. It should be possible if the deck is original as the plugs back then weren't polarized (with wide/narrow blades).
 
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I tried flipping the plug and it was easily done. It didn't seem to have any effect though. The very very faint hum was detectable in both orientations of the plug. Mostly, I am just wondering if this is normal, as apparently those in the AR XA thread, seem to say it is for that turntable, anyway. And maybe it's the same design for the AA RD11s.
 
I'm sorry but I can't accept one of the motor winding is left 'energized' in the off mode by design. It doesn't seem reasonable and I doubt it passes electric code regulations - even then. I've pulled the service manual US/Canada RD11S wiring diagram and added some color to it, so it's clearer for everyone:

9x27BDd.png


To me it seems the only ways for current to flow to the motor when the switch is disengaged (open circuit), is if either one of the capacitors is shorting.
Another possibility would rise if the switch lamp was swapped to an incandescent lamp instead of a neon lamp, or if the switch is faulty or wrongly wired.
 
^ actually... In an open circuit (off mode) the phase shift capacitor can short until the cows come home and current would still not flow to the motor. I'd check that arc-suppressor cap and make sure the switch and the wiring to it are good.
 
You write that the hum "continues" when you turn the switch off, but do you really mean the hum begins when you turn it off?

My Thorens TD160 and 145 both hum when the motor is turned off, if the two prong power plug is plugged into the outlet one way, or hum when the motor is on when it is plugged in the other way.
 
davstev said:
I tried flipping the plug and it was easily done. It didn't seem to have any effect though. The very very faint hum was detectable in both orientations of the plug. Mostly, I am just wondering if this is normal, as apparently those in the AR XA thread, seem to say it is for that turntable, anyway. And maybe it's the same design for the AA RD11s.
Click to expand...
You're probably correct. I just checked my Mission 775SM which uses a similar motor and switching scheme and it does indeed vibrate in the 'off' position. The plug is 3 prong so there's no chance it is plugged incorrectly. I hasten to add that the vibration is *very* subtle and completely inaudible, but the 775 is non-suspended and the plinth is quite heavy compared to the Ariston and other suspended decks. It seems the mass of the plinth effectively absorbs the subtle vibration to the point it is unnoticeable unless one actually touches the motor. Certainly, over the course of the more than the dozen years I've had this deck I've never noticed a hum while the deck was stopped or off, nor have I found it intrusive in normal use or I would've sold it a long time ago.

Very strange indeed, but must be normal for the type...:idea:
 
ripblade said:
You're probably correct. I just checked my Mission 775SM which uses a similar motor and switching scheme and it does indeed vibrate in the 'off' position. The plug is 3 prong so there's no chance it is plugged incorrectly. I hasten to add that the vibration is *very* subtle and completely inaudible, but the 775 is non-suspended and the plinth is quite heavy compared to the Ariston and other suspended decks. It seems the mass of the plinth effectively absorbs the subtle vibration to the point it is unnoticeable unless one actually touches the motor. Certainly, over the course of the more than the dozen years I've had this deck I've never noticed a hum while the deck was stopped or off, nor have I found it intrusive in normal use or I would've sold it a long time ago.

Very strange indeed, but must be normal for the type...:idea:
Click to expand...

This thread is getting stranger! My 775S (same as your 775SM, just armless, ASAIK) does not hum, either when the switch is OFF or ON. I do think I detect a very faint low motor noise when the stylus is on the record though. What would cause identical designs to be different?
 
ripblade said:
Did you take the belt off and touch the pulley? Physically touching it is the only way I can detect it. It is *very* faint.
Click to expand...

Gotcha. No, I haven't. Will do that next time I lift the platter. Nice to be discussing these *faint* noises with others who don't judge us as crazy audio nuts!
 
I'm just hoping that when I use the term 'faint' I'm not just describing the state of my hearing loss lol.
 
tnsilver said:
I'm sorry but I can't accept one of the motor winding is left 'energized' in the off mode by design. It doesn't seem reasonable and I doubt it passes electric code regulations - even then. I've pulled the service manual US/Canada RD11S wiring diagram and added some color to it, so it's clearer for everyone:

9x27BDd.png


To me it seems the only ways for current to flow to the motor when the switch is disengaged (open circuit), is if either one of the capacitors is shorting.
Another possibility would rise if the switch lamp was swapped to an incandescent lamp instead of a neon lamp, or if the switch is faulty or wrongly wired.
Click to expand...
Thank you, I am going to get my multimeter our and look into this and I'll get back to you.
 
doctor fuse said:
You write that the hum "continues" when you turn the switch off, but do you really mean the hum begins when you turn it off?

My Thorens TD160 and 145 both hum when the motor is turned off, if the two prong power plug is plugged into the outlet one way, or hum when the motor is on when it is plugged in the other way.
Click to expand...
I guess it's more accurate to say the hum (barely audible but definitely there), starts when the switch is turned off. Because when it's 'on', the motor is operating, so there's a small amount of predictable noise that comes from it. "hum" is really only audible when the unit is off. So you're saying that when your Thorens tables are "off" there's still a minor hum, 24/7, so long as it's plugged into the wall?
 
ripblade said:
You're probably correct. I just checked my Mission 775SM which uses a similar motor and switching scheme and it does indeed vibrate in the 'off' position. The plug is 3 prong so there's no chance it is plugged incorrectly. I hasten to add that the vibration is *very* subtle and completely inaudible, but the 775 is non-suspended and the plinth is quite heavy compared to the Ariston and other suspended decks. It seems the mass of the plinth effectively absorbs the subtle vibration to the point it is unnoticeable unless one actually touches the motor. Certainly, over the course of the more than the dozen years I've had this deck I've never noticed a hum while the deck was stopped or off, nor have I found it intrusive in normal use or I would've sold it a long time ago.

Very strange indeed, but must be normal for the type...:idea:
Click to expand...

My AA RD11s- also "*very* subtle and completely inaudible" as you say, in the off position. It just strikes me as odd, that's all. I assume that this kind of unit, when off, it's passing no electricity through it, which maybe isn't the case, and seems mildly worrying.
 
davstev said:
I guess it's more accurate to say the hum (barely audible but definitely there), starts when the switch is turned off. Because when it's 'on', the motor is operating, so there's a small amount of predictable noise that comes from it. "hum" is really only audible when the unit is off. So you're saying that when your Thorens tables are "off" there's still a minor hum, 24/7, so long as it's plugged into the wall?
Click to expand...

Depends on which way the two prong power plug is plugged into the power bar. One way, the hum is there when the motor is ON (so there when music is playing - very BAD!), or when the motor is turned OFF (which wasn't too bad on the TD160, but it bugged me on the 145, as it would come on with the auto-shut off, and I was hoping to use it in the bedroom system, but the hum would bug me if I was falling asleep - I know, FIRST WORLD PROBLEMS!). :P
 
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