Post by wdln on Aug 26, 2022 14:30:48 GMT
Hello all... I am working on an R-74 with the 1100 mech. About half the time when playing a record, the transfer motor dribbles past the two points where it should stop, i.e. ready to pull a record and record playing. It only goes a little bit past those points, but it's enough to cause issues. When the unit is in standby, sometimes the turntable motor is engaged. This is activated by cam switch 1, the first switch activated by the cam in a transfer cycle. Once a record has been loaded and the tonearm set down, it will sometimes go slightly past into the record unload cycle, the first mechanical action of which is to pull the tonearm up. It doesn't pull it up much, but it takes some of the weight off it and the record does not play properly.
I have performed the book's procedure for aligning the cam switches several times. As far as I can tell, they are working correctly, with the bump on the cam activating each switch only when the peak of the bump is aligned with the microswitch arm. The motor is simply turning slightly too far when it is de-energized.
My thought was: is there circuitry that should be acting as an electrical brake for that motor when the juice is removed? I'm not seeing anything in the schematic or step-through troubleshooting diagrams. The multi-pin control relay (R) is simply closing a contact to ground for the transfer motor to activate and releasing it to stop. Is there something inside the motor itself (or perhaps externally mounted) that I should be looking at, or should I just replace the motor altogether?
Or is it something with the timing of energizing and de-energizing control relay R, beyond what the cam switches are telling it to do?
I have performed the book's procedure for aligning the cam switches several times. As far as I can tell, they are working correctly, with the bump on the cam activating each switch only when the peak of the bump is aligned with the microswitch arm. The motor is simply turning slightly too far when it is de-energized.
My thought was: is there circuitry that should be acting as an electrical brake for that motor when the juice is removed? I'm not seeing anything in the schematic or step-through troubleshooting diagrams. The multi-pin control relay (R) is simply closing a contact to ground for the transfer motor to activate and releasing it to stop. Is there something inside the motor itself (or perhaps externally mounted) that I should be looking at, or should I just replace the motor altogether?
Or is it something with the timing of energizing and de-energizing control relay R, beyond what the cam switches are telling it to do?
