Teres Speed Control Tech Tip ============================ This Tech Tip provides background information about operation of the Teres motor along with all known problems and solutions. Background ========== First a little background on how the Teres motor works. The Teres motor has green and red LEDs that indicate status of the controller. When the motor first starts the red LED comes on to indicate that the controller is in spin up mode. In spin up mode the controller attempts to quickly bring the platter up to the correct speed. The green light comes on whenever the speed is within 1.5% of the correct speed. As the platter is spinning up the green light will flicker as the controller attempts to establish the correct speed. Once the controller has established the correct speed the red LED with turn off. This indicates that the controller has switched to a slow integrative mode that keeps the speed locked in and can only compensate for minor speed drift. If for any reason the speed goes out of tolerance after is has locked in the red light will come back on and the green light will flicker as the controller tries to again establish the correct speed. When this happens there is a clearly audible speed variation. This is by design. If the mechanical setup of the turntable does not allow the speed to stay in tolerance it is important to know about it so that it can be corrected. Unfortunately, this feature often is misinterpreted as a controller/motor fault. Any turntable drive system must be properly setup for good speed stability. The Teres motor quickly brings subtle problems to your attention so that they can be corrected. Symptom ======= Spinning the platter does not start the motor. Green light does not come on (not even a flicker). This indicates that there is no signal from the sensor. Possible Causes: 1) Sensor is plugged incorrectly. Earlier motors do not have a keyed connector for the sensor and can easily plugged in back-wards. Try reversing the sensor plug. 2) Defective sensor or controller comparator circuit. Symptom ======= The motor starts when the platter is spun. The green light flickers but does not come on solid. The motor often shuts off after a few seconds. This indicates an inadequate signal from the sensor. Possible Causes: 1) The sensor to strobe disk distance is incorrect. This is by far the most common reason for this symptom. The optical sensor must be 1-2mm from the platter (roughly 1/16"). This setting may be verified visually without removing the platter. When set correctly the the sensor will be above the top surface of base. The gap between the platter and the top of the sensor should be 1/3rd to 1/2 of the platter to base gap. If this setting is incorrect it is usually best to remove the platter and use the supplied gage to set the sensor height. 2) Defective sensor or controller comparator circuit. Symptom ======= After operating correctly for several minutes the motor suddenly speeds up or shuts off. Possible Causes: 1) Static discharge. As static builds up in the platter it can discharge through the drive string into the motor. This confuses the micro-controller resulting in a momentary loss of correct speed. In some cases the controller must be power cycled to restore proper operation. Grounding the bearing normally resolves this problem. The bearing ground wire should be connected to the preamp ground either directly or through the tonearm. Symptom ======= During play there is an audible change in speed. The red light comes on briefly. This symptom usually indicates a mechanical problem somewhere in the drive system. Possible Causes: 1) Grit in bearing. The Teres bearing has very close tolerances and a tiny particle of grit in the bearing can cause problems. To check for a bearing problem the platter must be removed. Without the platter installed the bearing should turn smoothly. The damping from the bearing oil will provide a fair amount of resistance but the bearing should turn smoothly. If the bearing does not turn smoothly it must be disassembled, cleaned and inspected. 2) Belt tension. If there is not enough belt tension the motor will be unable to maintain proper speed. It is difficult to describe the proper tension. However, a little experimentation will quickly establish how much tension is needed. 3) A minor bug exists in the firmware for motors sold between Dec 2001 and August of 2002 that can cause this symptom. With typical use this bug will very rarely be encountered. The firmware update that is part of the signature upgrade corrects this problem. 4) Belt alignment. For those with a grooved pulley (unlike the newer concave pulley) scrubbing of the drive string on the edges of the pulley can sometimes cause this symptom. Aligning the motor so that the sting runs more in the center of the groove makes operation more reliable. The motor alignment can be adjusted by placing thin card stock under the motor feet. Symptom: ======== Minor speed variances audible when listening. The red light does not come on. This indicates that there is uneven drag on the platter that still allows the speed to stay within the 1.5% tolerance of the controller. Minor speed problems will reduce sound quality but may not be evident as a speed instability issue. Possible Causes: 1) Grit in the bearing (see above). 2) Something rubbing on the platter. If the optical sensor is installed so that it touches the platter it will cause subtle but audible speed variations. Cable and wires may also be positioned so that they contact the platter and cause minor speed problems.