Tascam 644 midistudio tape deck problem

In the Teac X1000R this is most often caused by dirty Pinch Rollers and secondly bu a ring of oxide or a wear mark being developed into the capstan shaft. If cleaning the Pinch Rollers does not do it then a trip to the technician is required. These decks also have a touchy servo tension system that if upset can also contribute to the failure of this kind. I still work on these in Chicago area all the time. Russ the other ex-Teac guy is in New Jersey. Be careful of local shop with this model as many of them turn up the servo tension to resolve this problem which is the wrong thing to do that then burns out parts and the cost goes up. I have seen this mess many times as people bring me these decks as a last stop-- of course I fix then correctly with the use of the Tentelometer as is required. Pinch Rollers are often reconditioned with Naphtha after cleaning then with Denatured alcohol.
Teac Tascam Repairs Skywave Tape Deck Repair Bensenville IL

There is either a cam belt that is lose or the flywheel assist can not move the head base due to hardened grease. It needs to be serviced.

This condition, regardless of which way the tape is moving, is caused by the failure of a rubber pinch-roller to trap the tape between capstan and the passive roller.The speed is then caused by the part of the drive driven by a small belt and a clutch that should only keep a small amount of tension on the tape in ensure clean rewinding of the tape after it has passed the head.
Lubricant in part of the transport's moving parts or a dried-out rubber roller may be causing this.If you want to try to clean the pinch roller, don't use alcohol since this can further harden the robber.Use a clean fiber-free cloth or paper towel wetted with a LITTLE naphtha and turn the roller on the wetted area. If you get some dark smudging, the treatment is working.

There is a mechanism problem in the Pinch Roller part of the deck.
It needs to be looked at by a Technician to correct.

Sounds like a worn pinch roller.

Scott has a point. You need to determine what is causing the unit to stop and it could be a bad cam motor belt if it has one or the lack of take-up die to the bad idler or even a dead spot on the reel motor. The reel motor will work normally at high speeds due to inertia but at low speeds as are used in play the dead spot of the motor can become much more apparent.

You have not mentioned the model. Hope you have checked the belt and the motor that drives teh main capstain and the reel drives. If this does not work then replace and proceed. Also the pinch roller could be defective and not holding pressure to the spindle. Check the roller for hardening of the rubbers. replace if this is faulty. I hope with the set loaded with a tape you can find which drive is not spinning to take up. This should be able to confirm you with the right section. Hope this helps. Good day

There is an idler wheel behind the platen ( black plate behind the cassette)..replace the idler wheel.

The guy in texas is Marrs communications

No way to fix a bad pinch roller.Buy a new one from Tascam 323-726-0303 ex.840 is the parts dept.

Though not familiar with this model, VCRs of all sorts have an idler mechanism which drives the supply and takeup spindles. Either the idler is somehow defective and slipping, and, assuming this idler is belt driven, the belt may be slipping just enough to cause a no Rew/FFW condition. If you had access to a test tape jig (a clear dummy tape, which allows a tech to view what is happening in the area normally obscured by the loaded tape), this might give a clue as to what is happening. On alot of machines, a problem with Rew/FFW would also mean a tape takeup problem in standard play, result in tape spilling out inside the machine. Sensors would catch this condition and go into a error mode, as yours is doing. One other thing which might be happening here, is the pinch roller not being disengaged from the capstan in the Rew/FFW modes. I think this is where I'd look first, and you can probably see if such is happening just by pulling the cover off the VCR. The pinch roller is just to the right of the rotating video head. In the play and forward/rev search modes it will press the tape up against the capstan (a rotating shaft). When in Rew/FFW, the pinch roller should be pulled back from the capstan, maybe 1/4 inch or so. Whatever the case, repair will likely take someone tech savvy. Costs might not be economically justified, with the low-cost, disposable rigs sold in the last 10+ years.