This guide is intented to be an add-on to the DD center gear replacement tutorial. However, the adjustments in this thread do apply to all DD units, including the ones that do not use a center gear type mechanism (like the WM-D6/D6C, TC-D5M, WM-DD, WM-DDII, WM-D3, etc.). THRUST PLAY This applies to any walkman or cassette recorder, however not all have this setting adjustable. Ideally, this setting should be between 0.05mm and 0.1mm (on DD units it's recommended to be on the lower side, closer to 0.05mm). However, on WM-DD units where the motor spindle is always in contact with the rubber ring (WM-DD, WM-DDII, WM-DDIII, WM-DD30, WM-DD33, WM-DC2, WM-DD100, WM-DC2, WM-D3) it's prefferable to set it to 0.1mm instead to leave enough room for the other adjustment (as there is a relationship between the 2 on these units). When the thrust play is too high (this is set high by default on many belt-driven units), the pitch will change when moving the unit sideways or upside down. On big portables that are only meant to sit in straight position, this might not be a problem at all. However, on walkman type devices, that are moved all the time, the problem will be obvious. On the other hand, when there is no play, increased friction will decrease the tape speed, increase wow&flutter and decrease motor life. There are 2 methods of adjusting the trust play: 1. By measuring the current draw of the unit (the service manual method) You need to insert a multimeter in series with the battery terminals or DC IN jack (pay attention to the center negative and use a voltage a little lower than the rating). With the walkman put in PLAY mode, observe the current draw as you gradually tighten the screw. You will reach a point when the current will suddenly increase (because the play becomes zero). You need to stop at that point and rotate the screw a quarter of a turn (90 degrees) backwards and lock it with lock paint or super glue. 2. With a feeler gauge Put a 0.05mm feeler gauge between the flywheel and the back of the adjustment screw. Adjust the screw so you feel just a little bit of drag when you move the feeler gauge around. Lock the screw with lock paint or a little bit of super glue. 3. By feel The tolerance of this adjustment is pretty large, so you don't need a very exact adjustemnt, but you need to have it within a certain interval: - if it's too loose (like >0.2mm) the flywheel will move up/down when shaking the unit creating wow&flutter; - if it's too tight (like <0.05mm) the motor current will increase and there also won't be enough room to make the motor position adjustment correct even with screw at one end; This method requires some experience to know how 0.1mm of play feels, how 0.05mm feels, so chances are you won't be able to do it right if you haver never done such adjustments before. The thrust play is determined by 2 parameters: - the thickness of the thrust washer: usually made of nylon and placed between flywheel and capstan bearing; Unless this has been lost or replaced with a different thickness one, the play will remain the same. - the adjustment screw: it has lock paint on it from the factory, so unless it was tampered with previously, the play is the same as the one set from the factory. There might be some wear on the back of the screw, from the rotation of the flywheel, which can increase the play, or it might be set too loose from the factory. The back of the screw needs to be greased when the unit is serviced. NOTE 1: this adjustment is not influenced by installing a new capstan ring, but might need to be adjusted on WM-DD units because of relationship with other adjustment. NOTE 2: on WM-DD units where the motor spindle is always in contact with the rubber ring, there is a relationship between the motor position adjustment and thrust play. NOTE 3: FixYourAudio replacement rubber rings are thicker than the original ones (flat surface instead of conical). This means that on some units (where original thrust play is very small) you may need to increase it in order to have enough room for a correct motor position adjustment. To check this adjustment, move the flywheel up and down. NOTE 4: In order to be able to check this adjustment you need to press on the motor (DD units where motor spindle is always in contact with rubber ring) in order to remove the tension on the flywheel. Simplest way is to remove the motor entirely for the adjustment. It's relatively easy to make the screw too tight, especially on DD units, because the flywheel holding plate is very soft, deforming extremely easily without you noticing it.
MOTOR POSITION This adjustment is very important for the motor life, wow&flutter and mechanical noise. It's something that most beginners ignore, because it's not that obvious it needs to be done. In all DD units, you will need to remove the motor to replace the center gear/capstan ring, so that will mess up the motor's position. There are 2 axis on which the motor needs to be checked/adjusted. 1. Up/down movement relative to the flywheel. The position should be so that the spindle contacts the rubber ring fully, but it shouldn't be so inwards that it starts to have contact with the metal part of the flywheel. The rubber ring is wider than the spindle itself, so there is enough room for some error, it doesn't need to at an exact position. I adjust it so that the base of the spindle is in line with the edge of the flywheel. On units like WM-D6C and TC-D5 the adjustment is simply done by moving the motor around the screwholes, as the holes are larger than the screws themselves, allowing for adjustment. On smaller units like WM-DD series, the adjustment is done by bending the back of the motor bracket. You don't need to bend it much at all, usually 0.5mm to 1mm at most is all that's needed to make the spindle be in full contact with the ring. In some DD units that I have repaired, the bracket was not straight, causing this problem. Note that not all WM-DD need this adjustment done, but it's something to be checked. Position in this axis is important because when the spindle is not in full contact with the rubber ring, the spring that pushes the motor against the ring has less force, meaning an imperfect contact. This can lead to occasional slipping of the spindle, creating grooves in the ring. It can reach a point when the motor is freewheeling in a groove, not turning the flywheel at all. 2. Rotational movement (left/right) The position of the motor should be so the motor shaft is perpendicular to the flywheel. If this is not set right, there will be increased friction between the spindle and the rubber, creating wear, increasing mechanical noise, increasing wow&flutter and shortening the motor life (which is the most problematic, because there are not that many NOS motors available). - on units like D6C, TC-D5, the adjustment is done only by moving the motor around in its screw holes. You do not need any tool to do this correctly, eyeballing it is more than enough. It's not a micron precision adjustment, but it can be well off if it's ignored, which most people do because the play in the screw holes is not that high to give a second thought, but it's high enough to cause a significant mis-alignment. - on most DD series walkmans, there is an adjustment screw on the side of the motor bracket.
This thread should be pinned , thanks for your efforts mate for this and other of your posts . Keep it up !
