AMI Model K Gripper Mechanism
Here is a photo of the major components of the AMI gripper mechanism. This is before we had installed the turntable. The system operates on a 110 volt AC gear motor at the left. This drives a crank which connects to a connecting rod. The connecting rod connects to a cam which has gear teeth on top. This cam turns the gear on the left which begins the gripper cycle. This gear connects with a shaft to a gear on the bottom right of the gripper base. There are two gears on top of that which run the gripper.
The inner gear controls the motion of the gripper arm: forward and back from the carousel to the turntable. The outer gear controls the gripper jaws: either clamped on to the record, or free. These gears have some teeth missing, so that the gripper jaws and arm motion work only when they are supposed to at each phase of the cycle. There is a solenoid at the rear that controls the pivot point. This influences which way the gripper assembly will turn as it starts to come down toward the turntable: either to the left for "A" sides or to the right for "B" sides. The tone arm is activated by a cam that positions the tonearm on the record and allows it to track across the record while the record is playing, but moves it out of the way while records are being changed.
Here is the sequence of operation for the mechanism:
1. The gripper bow is positioned over the record carousel as the selection system scans for a desired record. The gripper jaws are open.
2. The selection system detects the desired record. The carousel stops. The gear motor begins to run, and the gripper jaw moves inward to grab the record.
3. Now that the record is gripped, the gripper bow begins to move upward. As it starts to move down toward the turntable, it hits the pivot point and begins to flip either to the left or right for the appropriate side of the record.
4. The record is laid down on the turntable and the gripper jaws retract, allowing the record to turn freely. As the record is being laid down, the tonearm is moving into position and sets down on the record as the gripper jaws retract. The tonearm is now moving freely, and the record begins to play. When the gripper jaws retract, switches activate by a cam to stop the gear motor and un-mute the amp.
5. When the record is done playing, the tonearm contacts a switch. The gear motor begins to turn again and pulls the cam back the other way, to reverse the cycle and put the record back in the carousel. When the record is laid back in its spot in the carousel, another switch activates to stop the gear motor and start the carousel turning again to scan for the next record.
You can see that proper timing among the mechanical components is essential for proper operation. If the gear timing is off, all kinds of problems can result, ranging from records not being picked up, to records being dropped or broken. We had to disassemble and thoroughly degrease this mechanism with Gumout, then re-set the timing and lubricate it with light turbine oil and Phonolube phono grease.
Here is a photo of the gripper in operation, with the turntable installed. Click the picture for a larger view.
We had been able to locate a turntable motor, turntable, and motor mount, which we then installed. Although the turntable ran well enough to play the record for testing purposes, it had some problems we had to correct. The next portion of the restoration we worked on was the Selection System.
Return To AMI Restoration Main Menu
Return To Retro Electronics Home Page