lost thread: LP12 motor mod

I know I saw a thread here some time ago about this, but I've just spent an hour searching :dead: and can't find it again... does anyone remember this? :confused:

There was a short thread about LP12 tweaks and mods that included directions on flipping the LP12 top plate so the motor would be ~180 degrees from the tonearm pivot instead of ~90 degrees from it.

Can anyone point me to that thread?

Thanks,

Ren
 
Thanks, Dan, but that isn't it.

It was part of a discussion about the possible benefit of having the motor, platter spindle, and tonearm pivot all roughly in a straight line:

motor === spindle === pivot

rather than the stock 90 degree configuration:

motor
||
||
spindle === pivot


A poster noted that he'd accomplished that on his LP12 by simply (?) flipping the top plate over and then remounting the motor, bearing, belt guide, etc using the original mounting holes. That would place the motor in the front left corner and the power switch in the rear left corner (viewed from the front).

Thanks!

Ren
 

YNWOAN

Member
2007-01-12 6:01 pm
One can do this, the only thing to bear in mind is that the LP12 top plate is bowed slightly so that when it is bolted to the plinth it is slightly under tension - if you flip it over the bow will be going the wrong way so you would have to pre-bend it in the opposite direction; also the top plate is not as nicely finished on the under side :) (the on/off switch will also now be in the back left corner).
 
I'd forgotten about the bowed top plate. The top plate on my LP12 seems perfectly straight when installed in the plinth. So, I assume the bow isn't large. Perhaps it won't upset things too badly when reversed. It'll still be stressed, but now in the opposite direction.

I thought I might try this tweak and see if I can perceive any difference (or even improvement :) ). If so, I'll probably take it apart again and find a way to polish the "other" side of the top plate.
 

YNWOAN

Member
2007-01-12 6:01 pm
It isn't bent very much no - but you're wrong I'm affraid when you say it will be much the same the other way up as the fixings that stress the bow are in the middle - the edges will be bowed up if you just flip it without bending it the other way and it won't be under any tension.
 
This "Bowed" top plate and plinth thing. Explain that to me. Is it part of the Linn Design philosophy? And what about the little wood screws that hold the arm board on. Is that done to compensate for bowed parts of the chassis? And while we're on the subject, my new platter seems a bit loose on the sub platter. If I didn't know better I'd think it was nearly a full mm bigger. Now when it plays the platter rotates in a precesional conic section like the Tilt-Whirl ride at the carnival. One of my guests actually became quit ill just watching it. We gave her some sea sickness pills which seemed to help, but getting the vomit off the SME V was another thing I'd rather forget. Someone told me I could set everything right by putting a four foot pry bar over the main bearing tube and giving it a good whack. The bloke told me this with an absolute straight face. He did not appear to be drinking, though I've noticed other dipsomaniac symptoms in this chap. He said "That's the way they do it in Scotland."
 

YNWOAN

Member
2007-01-12 6:01 pm
I will have a go :)

The bowed top plate is thus: the top plate is only (untill the much later introduction of the corner bolt near the motor) held in place by two screws which are central along the front and back edge. The metal plate is slightly bowed so that when it is screwed in place the bow ifs flattened putting pressure on the corners of the plate and so making the plate sit tightly against the plinth.

Linn always claimed that the three small srews were intended to provide a less than completely tight coupling between the armboard and the chassis and for that reason bolting the armboard in place would sound worse. However, this concept clearly does not apply to the Keel as the armboard and chassis are one piece and so could hardly be more completely fixed together.

Linn always stated that the outer platter was intended to be a very slightly loose fit on the inner platter to 'break the bell' and stop the components from ringing.

It has been known for main bearings to sit less than completely square on the chassis (as they bearing bolts via a remarcably small flange), and I have indeed heard of them being bent back into shape - I would not recomend this though and would rather source a new chassis. In addition a suspension bolt straightening tool was also made by Linn - a kind of T bar with a spirit level attached.