Joining the Reel World

Mar 1, 2007 12:00 PM, By Eddie Ciletti

Basic Maintenance

It's important to have a good visual view of the head area when doing maintenance. That is especially true considering the amount of oxide old tapes can shed. For best viewing, the deck should be horizontal. Place a piece of white paper in front of the head stack to reduce glare (see Fig. 2). Clean the heads with an alcohol-dampened cotton swab, using 99 percent (anhydrous) isopropyl or denatured alcohol. Do not use rubbing alcohol, which is 30 percent water.

Note that pinch rollers can turn gummy due to many factors, not the least of which is age. Whether it is real rubber or synthetic, the pinch (and other rubber-clad rollers such as the tachometer) will react to chemicals in the tape as well as in various cleaning fluids. For this reason I recommend cleaning all “rubber” immediately after a recording project is completed — not when starting one — so that the tape chemicals will not have a chance to be absorbed by, and do damage to, the pinch roller material. This will make the cleaning process easier, require less chemicals, and minimize the aging process.

Because it is likely that you will be buying a new pinch roller, the manufacturer will recommend (and I suggest that you purchase) its product-specific cleaner. For example, Athan's pink cleaning solution is water based, while MDI PrecisionMotorWorks' Head, Red & Roll cleaner is a more volatile, quickly evaporating elixir. Both are equally effective at cleaning their respective rubber products and most likely will not do damage if applied to another manufacturer's products. That said, if there is any doubt, consult the manufacturer.

To clean original rubber parts, start with a cloth dampened (not soaked) with a water-based product such as Windex, Fantastik, or Formula 409 (which also works well on ceramic capstan shafts). Wipe a second or third time with a water-dampened cloth to remove any residual dirt and soap. Do not allow liquid to go down into the capstan shaft, or the bearing and motor will be damaged. Avoid using consumer-grade rubber cleaners.

Demagnetize

There is only one head demagnetizer to own: the R.B. Annis Model 115-S Han-D-Mag (see Fig. 3). A demagnetizer with a switch is dangerous and should be discarded or repurposed to the school science lab. Note that powering a demagnetizer up or down in close proximity to recorders and tapes can do more damage than residual magnetism from the recording process ever could. If the following exercise does not yield results, do not demagnetize your recorder without help from someone experienced in tape machine maintenance.

All tools should be tested and demagnetized before coming in contact with the heads. If a screwdriver can pick up a razor blade, one or the other is magnetized. (The residual magnetism on the heads is far less and can be measured only with a very sensitive magnetometer.) Plug in the demagnetizer at least 3 feet away from tools, tapes, and machines, then practice by slowly moving the demagnetizer toward the screwdriver and then slowly away. Do the same with the razor blade and then confirm that the screwdriver can no longer pick up the blade.

The tape machine must be powered down before demagnetizing the heads, or you'll risk damaging a preamp. Power up the demagnetizer away from the machine, then slowly position it toward the erase head, moving up and down to cover the top and bottom tracks. While maintaining the up-and-down motion, slowly move the demagnetizer away from one head and toward the next. Also demagnetize the surrounding components — guides and lifters — although these are not typically made of magnetic material.

Check Your Parts

Using a tape machine requires a certain amount of electromechanical awareness. Each component in the recording and playback process — from the iron particles in the tape to the preamp required by the playback head — contributes to noise. For that reason, all tape machines boost treble when recording and use an inverse equalization curve during playback. The standard curves are AES, NAB, and IEC (formerly CCIR).

While some machines have all of these options, others have none. You need to know which curve you're working with before buying a test tape. For example, semipro machines are typically fixed for IEC EQ. Pro machines running at 15 inches per second can be either NAB or IEC. At 30 ips, AES is the standard EQ curve. EQ adjustments compensate for tape, electronic, and mechanical variations.

In addition to optimizing the signal-to-noise ratio, EQ adjustments compensate for tape and day-to-day electromechanical variations. The most obvious compatibility issue is a tape recorded on one machine and played on another, but even when a tape “lives” on a single machine, the performance can vary with temperature throughout the day.

Rolling

Considering the high cost of a test tape, do not attempt a playback calibration until you are sure the machine is operating properly. Here are a few DIY tips to determine whether a machine is in good working order.

Thread up a noncritical tape — but one that doesn't need to be baked — making sure the tape is wound snugly around the reel hub before pressing Play (see the sidebar “Baking”). Careless threading can stretch tape as well as bend or break guides, tension arms, and rollers.

Before it will do anything, the machine must recognize the tape's presence by using either a mechanical arm and a switch or an optical sensor. Some machines have mechanical brakes, while others use an electronic system. Once the tape is threaded, the brakes may release and the transport controls may be activated, or you may be required to press the Stop button. In the case of the Ampex ATR-100-series recorders, you will need to nudge the reels while pressing the Stop button.

Press Stop, then Play, then Stop: the tape should move forward and come to a gentle halt with no spillage or tension arm dropping. Next, fast wind to the middle of the reel from either end and press Stop. The tape should smoothly come to a halt in about the same amount of time in either direction. Any suspicious or dangerous behavior is reason to investigate or to consult a professional.

Now press Play and pay closer attention to how the tape passes through the guides, over the heads, and around the capstan on its way to the take-up reel. There should be minimal up-and-down tape movement and no tape-edge curling at the guides. (Use reels that are not bent or warped, so the tape edge doesn't scrape on the flange.) Some manufacturers, such as Otari, provided reel table shims to compensate for reel thickness or poorly adjusted reel table height.

Several mechanical issues can affect and exaggerate tape path problems: uneven tension on either side of the capstan, how “square” the capstan and other rollers are relative to the deck plate (the surface of the machine), or a pinch roller that has lost its shape. (Shimming the capstan or adjusting anything other than head azimuth is not for the squeamish or impatient.)

Any of these issues can cause the tape to skew up or down, and when things are really bad, the tape will curl and migrate out of the guides. Consult the manual for tension-measuring tools, techniques, and procedures. Fortunately, part of the head-lapping process includes a full mechanical alignment of the head assembly.