I am in the last stages of my fun tape control project and I am running into the problem of not knowing anything about things like servo damping or tuning servo response for these old capstan motors. Help!
Does anyone have experience with frequency controlled servo motors?
- Thread starter bgencarelle
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SkywaveTDR
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Tape speed devices are nothing but a closed servo system used to regulate the speed of a deck or flywheel according to the feedback that is provided through the FG wires or coils. There are more complicated units that allow for external speed reference clocks such as on the reel deck 42 or 52. You would need to study their servo systems and how that is implemented.
Often time it comes down to voltage amounts. Pots are adjusted to DC voltages. They provide a target voltage for the servo to shoot for. They put them into comparators. These then act to put out voltages to drive transistors that then drive larger transistors to ground a negative lead of a motor. The way the servo works is that there is a FG signal coming back from a magnet in the motor. This tells the servo the speed the motor is going. The frequency of the FG is amplified and converted through a F -V converter and that voltage is also put into the comparator. The servo tries to make the voltages the same and when not it either cuts drive or adds it to get the speed to what you have set it by the pot. That is the speed adjustment pot on a capstan servo control board- there are two of them selected by switch usually.
Often time it comes down to voltage amounts. Pots are adjusted to DC voltages. They provide a target voltage for the servo to shoot for. They put them into comparators. These then act to put out voltages to drive transistors that then drive larger transistors to ground a negative lead of a motor. The way the servo works is that there is a FG signal coming back from a magnet in the motor. This tells the servo the speed the motor is going. The frequency of the FG is amplified and converted through a F -V converter and that voltage is also put into the comparator. The servo tries to make the voltages the same and when not it either cuts drive or adds it to get the speed to what you have set it by the pot. That is the speed adjustment pot on a capstan servo control board- there are two of them selected by switch usually.
