How do I stop the tone arm assembly on my Vestax pdx2000 Turntable
from vibrating when I apply pressure to the platter (when the unit is
in operation with a slipmat)?

This Problem...
Happens on both of my tables (in a dj setup)
Happens regardless of the record on the platter
Started happening after I moved my tables to college (a couple days
ago)

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Request for Question Clarification by clouseau-ga on 03 Sep 2002 11:46 PDT

Hello mreder,

I need just a bit more information to help you here.

Are you really applying presure to the platter or just holding the
record and slipmat from moving as the platter turns?

Is there audio going through your system while this is happening? If
so, at what volume and how close to your speakers are your turntables?

Finally, please provide me with the brand and model of the cartridge
in your turntables.

I should be able to provide your answer with this additional
information.

Regards,

-=clouseau-ga=-

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Clarification of Question by mreder-ga on 03 Sep 2002 14:13 PDT

"Are you really applying presure to the platter or just holding the
record and slipmat from moving as the platter turns?"

Well, I am just holding the record and mat from moving, but if I
conciously hold as lightly as possible, the problem is not as bad. I
have also been able to replicate the problem sans record and mat, by
lightly pressing on the headshell while it is spinning and letting it
slide under my finger.

"Is there audio going through your system while this is happening? If
so, at what volume and how close to your speakers are your
turntables?"

Thinking that the problem might be due to magnetic interference from
my speakers or some other source, I tried hooking up a table in the
absence of any other equipment, and still had the problem.

"Finally, please provide me with the brand and model of the cartridge
in your turntables."

I am using Shure M447's. I feel it is important to tell you however
that I can duplicate this problem without even touching the stylus to
the record. The jitters seem to come from the actual tone arm assembly
itself, rather than the platter (though you can feel it to some degree
through the record). On the pdx2000's the tonearm is affixed to a
springy base, and it is this base that vibrates the most.

Also, I neglected to mention before that this problem is somewhat
unpredictable, sometimes it will not happen at all for a time and then
come on very strong, with no change to the setup.

One more thing, here is the text of a post I found on ses.djqbert.com
by someone who appears to be having the same problem:

"I think the problem is something loose in the tone arm setup because
when the i hold the record still and the platter is spinning it makes
these wierd vibrating noises. and if i like shake the table and the
needle is on the record you can hear them too.. if I hold onto the
tone harm and have the motor moving and hold the record i can feel the
arm vibrating a bit..."

Hope this helps,
mreder

Hello mreder,

You have a most curious problem here. If it were only one of your two
turntables, I would suspect a mechanical problem or a gross
mis-adjustment of the tonearm and tracking settings. But since it is
both, we need to look at something more in common with both
turntables.

As I'm sure you know, vibration can be born through the air or through
structure such as the floor, a table top, etc. Since you have this
problem intermittently and it can occur with no audio going through
your system and no record being played, it has to be structurally born
vibrations. Another clue that this might be the case is that they
seemed to work fine for you until you recently moved into your new
dorm room.

You mention:

"Thinking that the problem might be due to magnetic interference from
my speakers or some other source, I tried hooking up a table in the
absence of any other equipment, and still had the problem."

I was not thinking of magnetic interaction, but rather acoustic. But I
can rule that out if it occurs without any audio. Low frequency
feedback from speakers to a turntable CAN be below audibility and can
cause dramatic mistracking without the feedback becoming audible. And,
low frequency audio vibrations can also transmit through the walls,
floor, table, etc and cause mistracking. But if it happens with NO
audio signal present, this can not be it and it has to be structurally
born in your building.

Perhaps you can describe your physical setup? Where and on what are
the turntables? Where are the speakers?

Does the floor seem to flex if you bounce your weight in the room? Are
you near railroad tracks? Are you above or close to a laundry room in
the dorm? Are there automatic garage doors close by? What other
mechanical devices might be causing this vibration with no predictable
periodicity?

The reason I asked about cartridges was to determine the proper
tracking and anti-skating settings. It is very surprising, but common
for someone to set these too low for the application thinking that
less tracking force might create less record wear when that is
actually not the case.

Also, a mismatch between low compliance cartridges and high compliance
arms (or vice-versa) could be a culprit here. But not if it worked
well before and if it is intermittent now.

You also say:

"I am using Shure M447's. I feel it is important to tell you however
that I can duplicate this problem without even touching the stylus to
the record. The jitters seem to come from the actual tone arm assembly
itself, rather than the platter (though you can feel it to some degree
through the record). On the pdx2000's the tonearm is affixed to a
springy base, and it is this base that vibrates the most."

By chance, is there a transport lock on the suspension of the platters
that you locked before moving and have forgotten to unlock? Did you
remove the platters for transport and are they back into the proper
position relative to the drive motor?

I fear that these might be all the possibilties. 

Do check for transport locking mechanisms. Perhaps another researcher
will have more ideas and a solution for you.

Good luck.

-=clouseau-ga=-