Friday, September 6, 2013

Analog Tape Deck Alignment and Calibration

homepic[1] There are more than a few pretty good references on the internet describing the techniques for analog tape deck calibration. Before I list several that I believe are excellent resources, I have a few of my own comments to add to the history of this procedure. I’m not interested in reinventing the wheel, so I’m only going to add what I think might have been left out of the reference links found below.

There is a world of difference between consumer 1/4” (or 1/8” cassette) quarter-track machines and professional 1-2” 4-24 track equipment. Many of us first learned basic maintenance on 1/4” reel-to-reel semi-pro equipment before moving on to the real thing (pun intended) and we brought our toy-gear habits with us.

One of the first places that transfer will rear its silly head is in our procedures for cleaning heads and rollers. A small roller, like that found on the old Teac 3340 or Otari 5050 machines, can easily be cleaned with a cotton swab or two. Since the rollers are easily damaged (the oils extracted) by carbon-based cleaners (alcohol, TriClor III, etc), a cleaner designed for use on these materials is required. The most commonly available appropriate cleaner is mild soap and water applied to a clean, lint-free rag and some serious elbow grease. I recommend a near-white rag and that you keep cleaning until the rag stops removing material (which will be a while if the previous users attempted to clean the rollers with cotton swabs). Other techs have recommended MG Chemicals Rubber Renew, Caig Lab’s RBR100L Rubber Cleaner and Rejuvenator, Texwipe TX134, and American Recorder Technology’s S-21H Tape Head Cleaner. I, honestly, have used soap and water for the last 35 years and have no experience with other cleaners.

Likewise, most semi-pros started using cotton swabs and isopropyl alcohol to clean heads. The cotton swabs are, probably, fine if they are wooden stick swabs intended for non-hygienic applications. Plastic stick swabs sometimes decompose when exposed to head-cleaning chemicals, like isopropyl alcohol, and deposit gunk on the heads. While I am perfectly happy using cotton swabs on most professional heads, I’d prefer to us something like the Calrad Video Chamois to minimize abrasion and maximize surface area on large heads. Isopropyl alcohol is a perfectly acceptable cleaning chemical for this application as long as you don’t cheap out and buy “rubbing alcohol.” Additional chemicals and water are added to rubbing alcohol and I can’t guess what those contaminates will do to your expensive, hard-to-find, easily-damaged heads.

The “easily-damaged” bit is important to note, also. It doesn’t take much of a contaminate to turn a cleaning session into an abrasive head-damaging catastrophe. If you drop a swab on the ground, throw it away. Don’t risk scrubbing your precious heads with a bit of sand, dust, metal, or anything that might damage the heads’ surface or the gap. Some of the last generation of decks had heads that were nearly indestructible, except for the epoxies used for the gap. A bit of magnetic or conductive material ground into the gap and you’ve lost the ability to calibrate one or more tracks.

Professional tape decks all have mechanical calibration and maintenance procedures detailed in the owner’s manual. I recommend you follow those procedures, completely, ever 4-5 calibration sessions. There is no point in making sure your deck is perfectly calibrated and aligned if the deck can’t hold speed accurately, the tape lifters don’t quickly remove the tape from the heads during rewind or fast-forwarding, or if the tension between the capstan and take-up or supply reels is improperly calibrated and causes either lash or stretch in your tape. Every step of the transport calibration procedure is there for a reason and you should buy into those reasons and perform those procedures occasionally.

Detailed resources with near-step-by-step procedures and more information can be found at these locations:


Bradshaw Leigh said...

I would like to send you a free coupon to check out my complete analog alignment course. Here is a small youtube preview.
hope posting this is ok.

albina N muro said...

As I downsize my business presence, my internet presence will also vanish. Over the years of teaching audio engineering I've accumulated a lot of material that might be useful to all sorts of budding audio techs and musicians. NDT equipment calibration

Thomas Day said...

The real question is, "Does anyone care about analog recording?"

Wirebender Audio Rants

Over the dozen years I taught audio engineering at Musictech College and McNally Smith College of Music, I accumulated a lot of material that might be useful to all sorts of budding audio techs and musicians. This site will include comments and questions about professional audio standards, practices, and equipment. I will add occasional product reviews with as many objective and irrational opinions as possible.