"Grumps" wrote in message

"Phil Allison" wrote in message
...

"Arny Krueger"

A test record shouldn't be able to go off-centre. All
of mine are drilled small, and are a very tight fit on
the spindle.

Who says that the hole was necessarily drilled or
punched in the right place?

Where else do we get 0.55 Hz FM from?

** A defective belt will do that to a 33.3 rpm table.

Wouldn't the length of the belt have to be a multiple of
the circumference of the sub-platter (or whatever the
belt goes around) for that to be a cause?

IOW, a defective belt with dimensional issues is going to cause speed
variations that have a period that is based on its length divided by its
linear speed. The belt has to be appreciably longer than the diameter of the
driven member, so the period of its longest-term periodic contribution must
be lower than 0.55 Hz.

A belt could be defective, harden up and be so stiff that it did not provide
the desired low-pass filter action.

Also, a belt might get so hard that it slips, which may or may not create
variations that are based on the length of the belt.