AMI Model K Turntable
The AMI model K uses a regular rim-drive turntable, just like a home record player. You might think, "What's so difficult about getting a turntable to turn?" Well, it was about the most difficult and complicated part of getting the jukebox to work right.
First of all, we had no turntable motor, motor mount, or turntable, so we needed to order those. We found and ordered on ebay an AMI turntable assembly, but it turned out that is was from a late 60's or 70's model that uses the reverse-oriented tone arm and would not fit the model K. Then we found a jukebox parts supplier that had an actual model K turntable, motor, and mount. It fit right in, so we thought that that part of the job was done.
However, it was not to be that easy. When we got the gripper mechanism working to get records on to the turntable, the speed was very erratic. It turned out that the turntable was hitting a metal post used to attach the spring to the idler wheel. We later found that the bearing assembly to support the turntable was missing. When we installed one salvaged from a BSR turntable, this was able to alleviate the mechanical interference to the turntable, and the speed was even.
Now, though, the speed was way too slow. Someone had wrapped masking tape around the motor shaft to increase the "gear ratio" and increase the speed. We had removed that and thoroughly degreased and re-lubricated the motor, which usually clears up a sluggish speed problem. The speed was awfully slow...we put a strobe disc on it and found it was rotating at exactly 33 RPM!
We compared the diameter of the motor shaft to the 70's AMI motor which had 33 rpm capability, and found that the diameter of our new replacement motor shaft was exactly that of the 33 rpm portion of the 70's AMI motor! Now why they would make a motor for a 45-rpm turntable that would only do 33 rpm, we don't know. However these motors are VERY expensive, so we had to make do with what we had.
First, we tried to remove the shaft from the 70's motor and install it in to our "K" motor. It turned, but was too high, and hit the turntable when it was installed. So, we would have to "trick" the K motor in to running 45. First, we tried black tape around the motor shaft, but this created a rumble due to the un-uniformity of the tape wrap. Then, we tried heat shrink tubing. This resulted in a steady speed, but it was too fast! Slightly grinding down the tubing resulted in the right speed. We found that we needed to carefully super-glue the tubing to the shaft to get it to stay on.
We do not condone putting
anything on the shafts or idler wheels of a jukebox when it has its
proper motor: Resurfacing the idler wheel and disassembling and
throroughly cleaning the motor has brought back proper speed in every
other case. This replacement motor, though, was designed to give a 33
rpm speed so the heat shrink tubing trick was necessary.
Here is a record being tested on the turntable. We later found that the extra weight on the tonearm was not needed.
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