Why does the VPI motor thump


Why is it when I turn off my VPI motor I hear a thump through the loudspeakers? The only direct connection to the stereo is the belt.
last_lemming
VPI Tweak News: Just installed a 300 rpm motor and new larger on/off bypass cap. To be clear, the 300 rpm motor comes with a slightly larger sized cap than the 600 rpm motor. But I had to ask VPI to send me the larger on/off bypass cap. Absolutely no thumps. The motor is dead quiet. And the TT works just fine.

FYI for other DIY'ers: My version of the earlier Classic plinth has a circular metal disc which is hot glued into the plinth structure directly underneath the 600 rpm motor. Dunno if its the depth of the 300 rpm motor, or just the way the early version Classic plinths were made ... but the metal disc in my plinth had to be pried out or the new motor would not lay flush with the top of the plinth.

Removal required a flat-head screw driver. I just jiggled the metal disc out with the flat-head screw driver. VPI has a round rubber sticky that goes on the bottom of the 300 rpm motor. As best I can tell, the metal disc serves no purpose and the rubber sticky works just fine. Bottom line: no motor vibration or noise. Everything seems to work well.

Btw, this is a good time to clean and relube the main platter bearing with white lithium grease. Not sure I needed to put a tiny drop of oil into the new motor ... but did. Just a very tiny drop.

So ... for those who have a Classic TT with the 600 rpm motor looking to switch to the 300 rpm version, be sure to ask VPI to send along the larger on/off bypass cap and the rubber sticky thingy in the kit.

At this point, the only other tweak to turn my TT into the Classic 3 is the plinth. All other components are Classic 3.

Per Mat Weisfeld, there's not much more I can do to tweak the TT, except maybe for better feet, like Bear Paws. I have a DIY idea which may obviate the need for new feet.

Been thinking about building a sand box sub-base. I would cover the sand with a piece of thin rubber to prevent sand from getting into the TT. On top of the rubber covered sand sub-base goes my 35 pound 2" thick maple slab TT base, which I already own. On top of the maple slab sub-base goes the TT.

P.S. When my wife first saw the maple slab, she didn't get angry because I spent more money on my rig. Instead, she tried to take the slab for the kitchen Fortunately, it weighs 35 pounds and she gave up. :)

P.S.S. -- You may ask, does the new motor effect any improvement. Not sure. If there's an improvement, it's subtle. The main reason for doing it was boredom. Also, I'm sure it will make Stan (Stringreen) happy. :) LOL
Post Script to Stan (Stringreen): Stan, what are your thoughts if I paint my plinth with a shiny garnet black lacquer? It still won't be a Classic 3, but it may look like one. LOL

BIF
If a variac or SDS is used to manage the motor, there is no start up thump or pop.

I had the pop with both a TNT and an Aries motor. Currently using a variac on the Aries. Totally quiet start up and shut down. I turn on the variac when I turn on the preamp with the voltage set to 0v. I increase to 110 for start-up and and record brushing, then dial back to 60v for playback. When finished with a side, the voltage is doaled down to zero.

I like the very quiet background it provides compared to plugging the motor directly into the wall. Not sure I actually need something like a SDS because the speed seems OK.
Perhaps my system being totally balanced (all XLR connections) including turntable and everything else has something to do with it???
String, you're using a SDS. That isolates the motor. No thump. So does a variac and performs the most important functions of a SDS (isolation and voltage reduction) though manually.