by Bruce Bartlett

You just finished a perfect mix and recorded it on DAT. But when you play it back, you hear a glitch. It's either a noise burst or a short silence. What's going on, and how can you fix it?

Dust, pieces of oxide, or tape misalignment can cause errors in the digital signal. A glitch occurs when the DAT's error-correction circuit can't remove all the errors. Some DAT machines mute the audio when this happens, creating a dropout.

Errors are less probable if you use high-quality tape and keep the heads clean. Good tapes and clean heads usually give error rates well below 50. If you hear glitches, or if the error display reads high (over 100), it's time to clean the heads.

You can do this in three ways:

  • With a dry cleaning tape
  • With a wet cleaning tape.
  • Manually with a swab and cleaning fluid

Only manual cleaning gets to the entire tape path of rollers, tape guides and heads. Let's look more closely at each cleaning method.

The only maintenance that Sony recommends is a dry cleaning tape. They say that dirt on the capstan is not much of a problem. Sony does not recommend cleaning the pinch roller and guides unless you're used to doing it. Tape tension is more often a problem, and usually only in new machines.

A dry cleaning tape works by scraping the head drum to remove dust and dirt, trapping it in the tape fibers. To clean your DAT, pop in a dry cleaning tape and press PLAY. Eject the tape after 10 seconds. Since the tape collects dirt, do not rewind or reuse it.

If a high error rate can't be corrected by a dry-cleaning tape, send the DAT machine to the manufacturer's service department.

How often should you clean the heads? As little as possible, because the dry cleaning tape is abrasive. Use it only when you hear dropouts or when the error rate is too high. To be safe, clean the heads just before taping a live concert or a mixdown. It's also a good idea to run a redundant machine in critical situations.

"DAT tape doesn't shed as much as analog tape," says Rick Canata of Fostex tech service. So unless you're in a very dusty environment, he says, cleaning with a dry tape once a month should be enough.

One wet cleaning tape is DAT-101 from American Recorder/Intraclean, Simi Valley, CA, (805)527-9580. It uses a non-alcohol hydrocarbon based liquid that evaporates faster than alcohol. (Note: The company has stopped making this but has been in the process of re-formulating it to meet environmental standards, check with them)

Fostex does not recommend wet cleaning tape because excessive fluid can damage your DAT machine.

Bob Kozlarek of Panasonic tech service says, "Maintenance is more than head cleaning. Get the service manual for your machine and follow its periodic maintenance schedule. Use only an authorized factory service center. You'll be rewarded with a smooth-running machine." A VCR repair facility, Bob says, is not equipped to properly service DAT machines.

Manual cleaning is best done by a qualified technician. If you feel comfortable doing it yourself, proceed with caution. Jimmy Yamagishi of Tascam tech support says, "Order the service manual for the particular machine you're using, since they vary." The manual also shows lubrication points.

You'll need some foam-tipped swabs and cleaning fluid. Don't use cotton swabs because they can leave lint and can catch on the heads. Rick Canata of Fostex cautions against using chamois-tipped swabs or a chamois cloth because they can shred.

Some common cleaning fluids are denatured alcohol, freon-based chemicals, and halogenated hydrocarbon-based chemicals such as Intraclean S711. Alcohol is said to dry out rubber parts, so use a rubber cleaner on pinch rollers.

Clean everything the tape touches: the guides, rollers, pinch roller, and capstan. Dust and oxide deposits on the capstan can cause mistracking, so it's important to clean it. Half of the capstan is covered by a half-cylinder, so you can clean only part of the capstan at a time. To expose the other half, turn on the deck, load and unload a tape, and turn off the deck. If you do this a few times, chances are that all sides of the capstan will be exposed for cleaning.

To get at the head drum, you might need to disassemble the tape loading mechanism. Once this is done, moisten the foam swab with cleaning fluid. While holding the swab VERY GENTLY against the drum, turn the drum in one direction only. This action cleans the drum and each head. CAUTION: Keep the swab stationary. Don't move it up or down while it's contacting the drum, or you may break off the head. Neither I nor Cassette House are responsible for damage to your DAT.

Does your deck play its own tapes, but does not reliably play tapes from other decks? Most likely, the problem is tape-to-head alignment. You can't align the heads since they are stationary. But you can adjust the posts that guide the tape correctly past the rotating heads. CAUTION: This is recommended only in an emergency as a last resort. We are not responsible for damage to your DAT or DAT tapes.

Since the tape guides are slotted, you can turn them with a small screwdriver to change to path of the tape relative to the heads. Play your problematic tape and adjust the guides until the tape plays okay.

Exercise a blank tape before using it. Fast forward the tape to the end and rewind to the top. This loosens the tape pack so it travels freely, and spreads the tape lubricants more evenly.

Store tapes wound all the way to the head or tail. Store tapes on end. Keep them away from heat and magnetic fields.

Some manufacturers have DAT tech support hotlines:

Panasonic, "The DAT Help Line", 800-524-1448, 800-624-1746 inside NJ.Panasonic Pro Audio, 6550 Katella Avenue, Cypress CA 90630, 714-373-7277.

Sony "DAT Hotline," 908-SONY-DAT, 908-766-9328.

You can clean the I/O connectors with ProGold conditioning treatment, available from CAIG Labs, 16744 W. Bernardo Drive, San Diego, CA 92127, phone 800 CAIG-123, FAX 619-451-2799.

Many home studios have made the switch to modular digital multitracks (MDMs). Models such as the Alesis ADAT and Tascam DA-88 are selling like crazy. They're an easy transition from an analog 8-track, and they let you produce recordings of pristine clarity.

Like DAT recorders, MDMs can develop digital glitches. You can prevent these with some routine maintenance.

Tascam and Sony have similar units which need the same treatment. The only maintenance that Tascam suggests is cleaning the heads with a dry cleaning tape. Manual cleaning inside the unit is not recommended.

How often should you clean the heads? Whenever you format, and whenever the error rate becomes high. Basically, you exercise the tape and clean the heads before and after formatting. This ensures that the format data is clean. A glitch in the format data is harder to correct than a glitch in the audio data.

Tascam recommends this procedure:

  1. Start with a brand new tape of high quality.
  2. Fast forward the tape to the end and rewind to the top.
  3. Press and hold the UP-ARROW and DOWN-ARROW keys at the same time, and press POWER ON. The unit will go into cleaning mode.
  4. Pop in an 8mm dry head-cleaning tape. The tape will clean the heads for a few seconds, then will self-eject.
  5. Format the tape as described in the manual.
  6. Clean the heads again.

If a high error rate can't be corrected by a dry-cleaning tape, send the unit to Tascam service in L.A. or New Jersey. You might send in the unit for manual cleaning after 2000 hours of head wear, but the error rate is what really counts. To display the hours of head wear, press PLAY and STOP when you power up.

Error message ERR 1 indicates a mechanical problem, often cleared by ejecting the tape and resetting. Other error messages are for tech repair diagnostics of the transport.

You don't need to lubricate the transport, clean the fan filter, or reseat the PC boards.

The software version can be upgraded to allow faster sync, faster cleaning, and other features. Order version 3.03 from your Tascam dealer. It's an IC chip you plug into the unit. Phone other recording studios in your area, and ask if they have a DA-88 they'd be willing to loan if your unit fails. You can offer to do the same for them.

The Alesis ADAT and Fostex RD-8 need the same sort of maintenance.

Clean the unit whenever the error rate seems to be unusually high. Alesis recommends the 3M Blackwatch S-VHS dry head-cleaning tape. Sony V-25CLN is another choice. As for S-VHS tape, they suggest Alesis ADAT S-120 Mastering Audio Cassettes or Ampex 489 DM Digital Mastering Audio Tape.

Again, exercise a new tape before you use it -- fast forward to the end and rewind to the top.

Alesis will provide users a step-by-step guide to manual cleaning inside the unit. There's no need to clean the fan filter, reseat the PC boards, or lubricate the transport.

To determine the hours of head wear, push SET-LOCATE and STOP at the same time. The only error message concerning the user is ERR 7. It means one of three things: a tape dropout, dirty heads, or out-of-alignment. Other error messages are for repair tech diagnostics.

There's a new software version 2.0 you can install in the BRC Master Remote Control. It offers one-touch punch-in, a bigger MMC command set, better tolerance of SMPTE inconsistencies, and faster chase time to VTRs.

If your ADAT goes down, you can contact other ADAT users on the ADAT Worldwide Network. A nearby user might be willing to loan you their ADAT in return for the same favor.

Whether you're using the Hi-8mm or S-VHS format, I recommend that you always clean the heads before going on-location. If a glitch occurs in the field, you can't clean the heads and start over! If you do get a glitch and the error light stays on, try turning the unit off and on. Or eject the cassette and reinsert it.

Copyrighted 1995 by Deltamedia. May not be reproduced in whole or part without permission.