Doug G.
Lunatic Member
The tonearm height/brake pin and end-of-record cycle start are two separate issues. The height of the tonearm isn't related to whether or not the cycle begins at the end of a record.
The cork is an actual piece of cork stuck to the top of what is called the pickup arm lever which is connected to the tonearm at the pivot underneath the base plate. It is very thin and, as the tonearm is lifted by the cuing mechanism, the brake pin simultaneously lowers to contact the cork to hold the arm in position so it can't rotate while the tonearm is elevated. When the tonearm is lowered, the brake pin is released from the cork so the tonearm is free to pivot in normal operation. As discussed above, the tonearm needs to be at the correct height when the brake pin is released so it neither allows the tonearm to rotate before the stylus contacts the record nor keeps the tonearm from freely rotating after the stylus contacts the record surface.
The adjustment is made with the anti-skate set at a high level so the tonearm gets pulled outwar4d when the brake pin is released. This makes it easier to see when that actually happens.
The white donut in the return mechanism must be absolutely clean to maintain friction between it and the trip pawl and trip pawl plate so the trip pawl gets pushed into the path of the boss on the platter shaft so it gets shoved, moving the big red cam, starting a cycle by engaging the gear teeth.
The trip pawl is moved by the trip pawl plate, on the cam, being advanced by the pickup arm lever swinging over as a record is played. If the stylus is moving slowly, as when it is in the playing groove area, the trip pawl will just be pushed out of the way on each revolution. When the stylus reaches the runout area and moves quickly, the trip pawl moves fast enough to be pushed by the boss on the platter shaft and this starts the cycle. This is called a velocity-trip mechanism.
Some have used small, regular O-rings to substitute for the white donut but the coefficient of friction must be the same so there isn't TOO much friction which would cause too much force to be required to push the trip pawl out of the way during record play. That is why I would always try to save the white donut if at all possible.
Doug
The cork is an actual piece of cork stuck to the top of what is called the pickup arm lever which is connected to the tonearm at the pivot underneath the base plate. It is very thin and, as the tonearm is lifted by the cuing mechanism, the brake pin simultaneously lowers to contact the cork to hold the arm in position so it can't rotate while the tonearm is elevated. When the tonearm is lowered, the brake pin is released from the cork so the tonearm is free to pivot in normal operation. As discussed above, the tonearm needs to be at the correct height when the brake pin is released so it neither allows the tonearm to rotate before the stylus contacts the record nor keeps the tonearm from freely rotating after the stylus contacts the record surface.
The adjustment is made with the anti-skate set at a high level so the tonearm gets pulled outwar4d when the brake pin is released. This makes it easier to see when that actually happens.
The white donut in the return mechanism must be absolutely clean to maintain friction between it and the trip pawl and trip pawl plate so the trip pawl gets pushed into the path of the boss on the platter shaft so it gets shoved, moving the big red cam, starting a cycle by engaging the gear teeth.
The trip pawl is moved by the trip pawl plate, on the cam, being advanced by the pickup arm lever swinging over as a record is played. If the stylus is moving slowly, as when it is in the playing groove area, the trip pawl will just be pushed out of the way on each revolution. When the stylus reaches the runout area and moves quickly, the trip pawl moves fast enough to be pushed by the boss on the platter shaft and this starts the cycle. This is called a velocity-trip mechanism.
Some have used small, regular O-rings to substitute for the white donut but the coefficient of friction must be the same so there isn't TOO much friction which would cause too much force to be required to push the trip pawl out of the way during record play. That is why I would always try to save the white donut if at all possible.
Doug
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