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Fitting Belt and Adjusting Platter Speed
Parts required for this step:
- Motor pod
- Drive belt(s)
- Battery power umbilical cord
- Battery
This step is normally performed after the tonearm is installed. Because of the small learning curve involved in adjusting the belt
height and getting it to track properly, we recommend that you familiarize yourself with the process before mounting your precious
cartridge.
You will be learning a few new tricks in this step, and it's best to leave vulnerable parts out of potential harm's way the first time
you perform this operation.
This step is the only counter-intuitive part of getting your turntable running optimally.
An understanding of the principles involved will guide you towards not only an understanding, but an appreciation of the elegance of
this simple solution.
The object of this step is to balance out two opposing constraints:
- Minimizing side load on the motor bearing
- Maximizing the grip that the belt has on both the pulley as well as the platter
We've found that using excessive belt tension reduces dynamics - even though it maximizes the belt's grip on the pulley and platter.
Conversely, too loose a belt tension is friendly to the motor bushing but results in too much belt slippage.
An optimum tension is easy to set if you follow these simple steps:
- Locate the motor pod on the turntable shelf.
- Plug the power umbilical into the motor pod but don't plug the other end into the battery. Make certain that the 3 way switch
(on-off-on) is in the center (off) position.
- Install the belt around the platter and motor pulley.
- Locate the belt height so that it runs approximately in the center of the area of the platter where there are no grooves.
The belt should be positioned mid-height on the pulley.
- Set the initial tension to a fairly light pressure.
This can be measured by the distance that the belt deflects with light pressure from your finger.
Press on the belt at the midpoint between the motor pulley and where it releases from the platter.
A gram or two of force should deflect the belt from 1/4 to 1/2 inch.
- Make sure that the belt tracks properly
As you follow this step, you will quickly learn that the belt's position on the platter determines whether it will track the
pulley or run off of it.
The belt's overall rigidity contributes to the sound of the turntable but also means that attention must be paid to locating it -
unlike rubber belts whose only virtue is that they can be simply installed.
- Slowly rotate the platter by hand (1/4 of a turn or less, at first) and watch the position of the belt on both the platter
and the pulley.
- If you notice that the belt starts to "walk off" the top of the pulley, stop rotating the platter.
Gently slide the belt
downward on the platter - along the entire platter area that the belt contacts.
- Similarly, if the belt starts to walk off the bottom of the pulley, stop rotating the platter and raise the position of
the belt on the platter
- After a few tries, the belt will track the pulley over several complete revolutions of the platter.
- Reset the belt tension as described above.
- Place the Anvil on the record spindle along with your strobe disk of choice.
- Plug the controller umbilical into the battery, turn the switch on the motor pod to the right while giving the platter a
helping push-start.
The blue LED should light
- Adjust the pot adjacent to the blue LED so that the platter turns at 33 rpm.
- Now, very carefully, move the motor pod in small increments - first, increasing the belt tension.
Observe whether the platter speeds up or slows down.
- If the platter speeds up, continue slowly increasing belt tension until you reach maximum speed.
- If the platter slows down, slowly reduce belt tension until the platter no longer speeds up any further.
- You will likely overshoot the "sweet spot" and have to return to it. It's not critical to be exactly "spot on",
but rather to find the general area where the platter spins the fastest
- At this point, you should find that the belt tension is such that if you were to loosen it, the belt would show a
slight bit of flutter.
Don't loosen it to this point, although we have observed good speed stability with Mylar belts set so loose as to
flutter slightly.
If you were to measure the belt deflection you should find that 1 gram of force would deflect the belt about 1 cm
- At this point, re-set the speed to 33 rpm.
- Flip the toggle switch to the left - past the off position to the 45 rpm position.
The red LED should light
Adjust for 45 rpm using the pot adjacent to the red LED.
Note that your turntable bearing oil will warm up over the course of about a record side.
At this point, you will note that the turntable speeds up ever so slightly. This is normal.
Re-adjust the speed at this point and you will have set the pots for a warmed-up condition. We've found that feedback circuits
could control the speed, at the expense of overall sonics.
Like the rest of your system, it will sound optimal after a short warm-up.
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