Vintage DD turntables. Are we living dangerously?

Chris, this is from the manual for my SP-10 Mk2A:

"The quartz phase-locked control system and the DC servo motor with large torque can maintain each rated speed of the turntable even with a load torque of up to 5 kg-cm (4.3 lbs. in.). If 500 tonearms of 2 g. tracking force were placed on a record at the same time the turntable would still maintain each rated speed."

From the way this is stated, I assume it applies to the sum of the weight added on top of the platter. There was an accessory Audio Technica disc stabilizer (vacuum) designed for placement on top of the SP-10 platter (perfect fit after the mat was removed) which I believe weighed 1.4 kg. So mats heavier than the standard rubber mat have been used.

Where to begin?
Dear Gary, Henry makes a VERY good point; if you have plugged your TT101 into the 120V wall outlet, that could very well be what is making your transformer hum. Even though the voltage is only slightly different from 100V, you had best use a step-down transformer. You may eventually damge the TT101, otherwise. They are available on eBay. You only need one that can handle 50W or slightly less.

BUT I am not clear on what you are hearing. In your last post it sounds like you may indeed be hearing hum through your speakers. If so, this is unlikely to be due to the power transformer. Look for another cause. As for EMF, the transformer and turntable motor are emitting EMF no matter whether they are noisy or not. I use a shield on my (coreless) LO7D motor (between the platter and the platter mat, made out of TI Shield available from Michael Percy). There never was any hum problem with LO7D; the shield reduces or removes a kind of gray-ish glare that colored the L07D output. TI Shield blocks both EMI and RFI. If you are hearing only a local mechanical hum directly from the tt, then go back to my first paragraph. If you are already using 100V step-down, then you just have one of those transformers that hums. Try reversing AC polarity; sometimes that helps.

Dear Henry, Of course you have to tap the shelf!!! The node will be at the same place regardless of how you stimulate the shelf to vibrate, so the result achieved by tapping and listening with the stethoscope is always valid. However, I do not think this has much if anything to do with airborne vibrations. This has to do with structure borne vibrations emanating from your environment. Even a wall is not inert, as you know better than I do. Plus there is the issue of micro-seismic activity. And your huge feet clumping around the room as you dance to the music.

When I was a medical student, everyone wanted a Littman stethoscope. But there is at least one other very good brand. I have not only two of my own but the one that belonged to my father, from before WWII. A�nd my wife would lend me hers in a pinch. (That is, if I pinched her.)

Gary AND I should have written "EMI", not "EMF". EMF stands for ElectroMotive Force, which is another term for voltage. EMI stands for ElectroMagnetic Interference, which is undesired low frequency radiation from a transformer or motor. I picked up on Gary's error in my response.

Lewm,
EMI it is. I can only hear the vibration using the stethoscope pressed against the plinth or top plate, not through the speakers. It is faint, not audible with naked ears (at least mine). It doesn't change with a reversal of the plug. What reduces it the most is damping the sheet metal cage on the underside of the table using a squash ball suitably squashed against the shelf.
The table was sold in Los Angeles, CA (it has an import stamp) and is actually part of a QL10. The QL-10 is three separate components: A TT-101 direct-drive turnable, a UA-7045 tonearm and a CL-P1 base board, combined and sold together. On the rear of the plinth is a metal plate showing 120V, 60hz, 23W. I am using a Technics EPA-100 that I had rebuilt by Jim Howard rather than the UA7045 at this time.
I am making inquiries on moving the AC power components into a separate box - I refer you to KAB Electro Acoustics, KAB PS-1200GX as an example of what I would like to do but can't see how I can, but I can have the transformer, etc. moved. And I will if it is reasonable. I am also going to order that TI shield. Thanks for that tip.

Based on your last post, I would not worry one bit about that hum. (Obviously your TT101 was built for 120V.) But if you like to worry, I still would not go to a lot of trouble and expense to move all the electronics out of the tt chassis, if indeed it could be done with the TT101, which as H pointed out is quite complex, and quite a bit more complex than an SL1200.

Do you like the EPA100 significantly more than the UA7045? I always thought those Victor tonearms might be sleepers and have been tempted at times to buy the 12-inch version.

The TI Shield is not going to kill the hum, because the hum is of mechanical not electrical origin, but you might find it benefits the sound and is definitely worth the effort. I ordered a 12 X 12" sheet and cut it in the shape of an LP, so it fits under my tt mat and does not show. For best results, it should be grounded to the tt chassis. If your platter is made of anything conductive, e.g., alu, that should take care of itself. Let me or let us know if the TI Shield cleans up the sound in surprising ways.