Teac Tape Tension/Skewing Problems – X-series, Dual Capstan Models

Teac head

Several of the Teac X series of tape decks, both the 7” and 10” machines, are dual capstan drive machines, which means there’s a pinch roller and capstan shaft on either side of the tape heads. The design is such that the dual capstans keep the tape tension even over the tape head path, reducing head wear, and (supposedly) maintaining tape alignment over the tape heads.

When the X series decks work properly, they work well, and fidelity and performance is great in both directions. When there’s a problem in the tape path however, the dual capstan mode can be a big nightmare.

The Teac dual capstan models are unique, in that the main capstan belt actually moves forward and backwards on the flywheels, depending on the direction that the tape is playing. The diameter of the flywheels change slightly depending on the position of the belt, making the capstan shaft closest to the take-up reel spin ever so slightly faster than the one closest to the supply reel, which maintains the tape tension. If there’s a problem with any of the tape path areas, or with the parts that control the  tape tension/path,  the tape can skew off the tape heads, or can actually drop right off the  head completely, in a ‘U’ shape between the  pinch rollers, within 30 seconds of pressing ‘play’. One direction of play may work fine, or both directions of play may be problematic. Of course, the tape skewing problems can also be intermittent,  with no problems seen through several tapes, and then a tape or two may not work at all in play mode.

Here’s some of the common problems related to tape path problems:

A clean tape path.

This is by far the most important  thing to do with all reel to reel decks, but with any dual capstan motor deck, it’s even more important. ‘Did you clean the tape path?’ is the most common question that I ask, usually 3-4 times daily. On this particular X-1000R deck, the client stated that he had indeed cleaned the heads. When I got the deck in for servicing, yes, the heads were pretty clean, but every tape guide, and more specifically, the capstan shafts were covered with oxide, coming off of old tape. With even the smallest bit of oxide buildup on the capstan shaft, the speed of the capstan shafts are now changed ever so slightly, and the tape can skew. The larger buildup of oxide just outside of the tape path causes even more capstan speed variations, and if the tape moves up into that buildup area, the capstan speed is changed even more. See the below pictures for the amount of oxide and gunk that came off this deck.

Massive oxide buildup on the capstan shaft of an X-1000R, with additional buildup on the tape guides on the side of the heads.

The customer complaint of the tape skewing, solely caused by the oxide buildup on the capstan shaft and on the tape guides.

5 fully loaded cotton swabs full of oxide, coming off the tape guides and the two capstan shafts.

After cleaning, without any other adjustments done to the X-1000R, the tape is now sitting where it should on the tape path.

The correct belt

Stretched and the main capstan belt gone gooey are very common on all Teac X series, especially if the belt is the original Teac one. Unfortunately many sellers on eBay and online sell belts made by Russell Industries out of New York. While their belts are of excellent quality, their cross reference is incorrect,  and their recommended belt replacement is too thick as compared to the original. With the belt making a sharp U turn around the motor pulley, the incorrect belts can bog down the motor,  and cause the capstans to spin incorrectly. Some belts also will not change properly on the flywheel when the reverse direction is selection, causing tape spillage and skewing. The only seller we’ve found that sells the original Teac OEM belt is Dave Sherrington out of Boulder, Colorado, His seller nickname on eBay is Dave  N S. Yes, his belts are $8-10 more expensive than other eBay sellers, but spend the money to get the right belt. The Russell Industries belt, size FR 16.9 will NOT work properly, regardless of what other eBay sellers say.

Worn pinch rollers

Despite many clients telling me ‘I cleaned the pinch rollers, they’re fine’, they may not be. Again, we’re talking 1000ths of an inch here, that the pinch rollers can be out of round, causing tape skewing, so the pinch rollers being perfectly round are crucial for proper deck performance. If the pinch rollers are original, they should be sent to www.terrysrubberrollers.com for rebuilding. Even if the pinch rollers are round, they can still harden up, causing improper pressure between the capstan and the pinch roller.  No matter how good your eyesight is, you won’t be able to tell if a pinch roller is out of round’. If you have original pinch rollers, send them to Terrys. (you wouldn’t run your car on 50 year old tires, why run your tape on old rubber!).  www.terrysrubberrollers.com


The original Teac pinch roller is on the left, a replacement from Terry’s is on the right.

Thread the Tape Properly.

We’ve seen some tape skewing problems due to the tape being threaded incorrectly. To the left of the head stack is a pin that is directly to the right of metal idler roller. That is one of the auto reverse sensor pins that will change the tape path direction when the metal foil strip moves over it. Some people thread the tape under  this pin, and that’s incorrect, and puts stress on the tape. Follow the owner’s manual for the correct way to thread the tape. Putting the tape under the pin can and will cause tape skewing.

Incorrect way to thread tape on a Teac X series.

Correct way to thread tape on a Teac X series.

Pinch roller pressure and tape tension adjustments

Most Teac models (although not all) have physical pinch roller pressure adjustments within the deck, and two or more trimpots located in the electronics of the deck to adjust take-up and supply reel tape tensions. We’ve seen the trimpots go intermittent due to age, however we caution against touching anything within the deck unless you have the proper spring gauges and a working tentelometer, you cannot set up this critical part of the tape path. Too low of tape tension, and you’ll have tape skewing problems, too much, and you’ll put premature wear on the heads. Don’t touch this unless you know what you’re doing! (that’s why we’re not providing more information here).