In the last two posts we have been looking at a very cool Sony TC-355 reel-to-reel tape machine that is in desperate need of repair. While the backward function worked, the forward and fast forward functions did not. Now we will see about the fix.
Once the internal components were cleaned and lubricated properly, the next thing to do was to sort out why the pinch roller was not pinching against the tape drive capstan. That roller is circled in the above image. When the selector lever is changed to Forward, this roller is supposed to move up and in toward the capstan. Why was this not happening?
In the above image we see the root of the problem. The metal lever arm pivots on a spindle. The arm is partially pulled off of the spindle in the photograph. The old factory grease was petrified and prevented the arm from swinging on the spindle.
A horizontal spring, we can see a little bit of it, connects the arm to the frame of the heads assemble. The spring is strong, but not strong enough to overpower the old grease. The spindle of the pinch wheel goes through a hole in the arm.
Movement of the selector knob causes the lever to pivot. That in turn moves the pinch wheel against the drive spindle while at the same time a cam causes the wheel to move up into “pinch position”. The spring pulls the arm back when the selector knob is returned to the off or neutral position.
Once the pivot spindle was cleaned are re-lubricated the whole assembly worked like new. The whole thing was extremely smooth.
In the photo above we see a closeup view of the pivot spindle with the lever arm partially removed. There was, in fact, very little factory grease left on the spindle, but what there was, well, it was hard and nasty. To remove the lever arm I had to very carefully use a heat gun to soften the old grease and slide the lever arm off.
After cleaning and re-lubrication it was time for reassembly.