Forward back tension is tested and adjusted by using the tool shown above. It is a specially designed cassette that has two torsion reels with a small amount tape on them and flat coiled springs wound around inside. The reels are each made in two sections, these are the inner and the outer hubs and they can move independently against the springs attached between them. To see their internal construction click on the picture. Around the perimeter of the outer hub is a scale and on the center one is a pointer (removed in this photo). When the tool is loaded into the machine and play or record is requested the inner hub pulls against the outer using the spring. The outer hub will turn only in relation to the capstan speed and the inner pulls in relation the force exerted by the reel motor. The difference of the pulling force against the outer hub (tape travel) is what is being measured. The outer hub with the scale moves around inside the inner and gives an approximate grams per centimeter reading of how much force is being exerted on the tape. This measuring process is shown in the next photo. The supply hub on the left (back tension) is showing a reading of about 44 grams, which is ideal. Remember from our past discussion that the spec in the manual is 45 ± 5 grams. The scale on the right side is measuring the force (tension) of the take up reel and here we see 79 grams and the spec is 80 ± 5 grams, this is good also. Click on the picture and you'll see a test cassette I've altered. My reason for me doing this is that most machines are designed to sense if the forward reel doesn't rotate within a specified time period. Since it takes at least one revolution for the torque tape to steady and register on the dials. This rotational delay causes some machines to see this as a fault and shut down which makes getting an accurate reading difficult. The service manual instructs the technician to make a temporary electrical alteration to the machine to overcome this. I find this time consuming and that having this special torque tape is much quicker, easier and more practical. To adjust and meet the necessary tension and torque specifications there are several procedures to perform, to see how this is done click here. ©Misterßetamax go to homepage