Johny B Good wrote:

I'll try it on 1.6g and see what happens, but I am not very impressed by
the way it was installed.


It seems to me that it may be something wedged around the tone arm
pivot (you mentioned a cartridge change in your later posting). If you
can, take a closer look at the cartridge lead wires where they exit
the tone arm and verify whether or not they are misrouted in such a
fashion as to create the effect of springy 'end stop'.

No, there was no springiness at the end, but the arm wasn't adequately
weighted, and probably the bias was set incorrectly.

Some manufacturers (B & O being one that comes readily to mind) did
try to eliminate this issue by using a servo tracked arm hanging off a
slide bar and lead screw assembly running parallel to 90 degrees wrt
the tangent of contact of the stylus tip with the groove. It certainly
solved the sidethrust issue but introduced other issues (which,
afaicr, may have been more significant that those in the traditional
arrangement - quite possibly the idea was simply dropped due to the
relatively high cost and added complexity for a marginal improvement).

I knew someone in the 1980s who, for his Sixth Form electronics project,
designed and built a parallel tracking tonearm using parts from a model
train set.

There is one thing I don't understand about bias though.

It seems to me that since the spiral groove moves the needle inwards, it
must be the face of the grove that's towards the outer edge of the
record that's exerting a force on it.

In other words, if the groove were a wide U-shaped-channel rather than a
V, the needle would be pushed inwards by the wall of the channel on the
outside.

So I'd expect there to be higher pressure from the needle on that face
of the channel.

Yet bias adjustments exert a force moving the tonearm outwards, in the
opposite direction, which seems to me will further increase the pressure
on that wall, whereas to eliminate it, the bias should encourage the arm
to swing towards the centre.

Daniele