RT 909 some tapes do not move

[Cotonou]

I restored as good as I can an RT 909, tapes play, and recording work as well.
Some tapes however (like an lpr35 from RMG) - despite threaded correctly - make the pinchrollers and capstans clank in normally when pressing play but they do not move. They rest immobile.

Using an Maxell 35-180B on a Pioneer spool works however without any flaw.

Any idea where I should look at? Both tapes have been threaded the same way.
The releasing contact on the spring levers on both side work. Fuses are all ok,.

What can cause the capstan wheels to block? Something blocks the movement of the LPR tape.

 

[oldvinyldude]

To clarify, when you use the LPR tape, the pinch roller engages, but the capstan motor shaft does not turn? When the Maxell tape is threaded, the pinch roller engages and the capstan motor shaft spins, and tape travel is normal?

 

[Cotonou]

Exactly! I will try to reproduce it and record it with a camera.
The rollers seem to be hold by something, they are like held by something.

 

[pustelniakr]

A different tape making the difference between capstan spinning and not spinning makes no sense. There is no mechanism that would be that sensitive to tape differences. Now, what you describe could be caused by incorrect pinch roller pressure. If the pinch roller does not press against the capstan with the proper pressure, the machine will not drive tape, since reel torques are too low to move tape. Put on the tape that won't drive and press the pinch roller up against the capstan and see if that makes the machine want to drive tape. If so, do the pich roller pressure adjustment.

Enjoy,
Rich P

 

[stereoguy70]

A different tape making the difference between capstan spinning and not spinning makes no sense. There is no mechanism that would be that sensitive to tape differences. Now, what you describe could be caused by incorrect pinch roller pressure. If the pinch roller does not press against the capstan with the proper pressure, the machine will not drive tape, since reel torques are too low to move tape. Put on the tape that won't drive and press the pinch roller up against the capstan and see if that makes the machine want to drive tape. If so, do the pich roller pressure adjustment.

Enjoy,
Rich P

I had this exact problem with the Teac A-4010S that I recently got working again after years of storage. It would play tapes fine on the 7 1/2ips speed, but on 3 3/4ips the tape would slow and wow & flutter went through the roof. Sometimes the tape would come to a crawl and stop. I tried cleaning and then polishing the capstan with an emery cloth, and also ran the same emery cloth against the pinch roller. This helped, but the real fix as you said was adjusting the pinch roller pressure. Ideally the real fix will be a replacement pinch roller when I get the $$.

 

[dhnash]

I had this exact problem with the Teac A-4010S that I recently got working again after years of storage. It would play tapes fine on the 7 1/2ips speed, but on 3 3/4ips the tape would slow and wow & flutter went through the roof. Sometimes the tape would come to a crawl and stop. I tried cleaning and then polishing the capstan with an emery cloth, and also ran the same emery cloth against the pinch roller. This helped, but the real fix as you said was adjusting the pinch roller pressure. Ideally the real fix will be a replacement pinch roller when I get the $$.

Texturing the pinch roller in this manner is probably what initially helped in this situation. The polishing of the capstan with emery cloth may have actually been detrimental since smoothing the capstan would reduce the friction between its surface and the tape. Texturing the capstan surface using a pinch roller wrapped in sandpaper has been discussed in other threads as one method to improve tape handling at the point where the capstan and pinch roller contact the tape. As you said, using a good pinch roller and properly adjusting the pinch roller pressure are important to achieving good results.

 

[stereoguy70]

Texturing the pinch roller in this manner is probably what initially helped in this situation. The polishing of the capstan with emery cloth may have actually been detrimental since smoothing the capstan would reduce the friction between its surface and the tape. Texturing the capstan surface using a pinch roller wrapped in sandpaper has been discussed in other threads as one method to improve tape handling at the point where the capstan and pinch roller contact the tape. As you said, using a good pinch roller and properly adjusting the pinch roller pressure are important to achieving good results.

I used very coarse emery cloth when I used it on the capstan. I figured to give it some "tooth". It did seem to help at the time.