6 Track Mag Head Maintenance

[Ryan Gallagher]

Query. What is best practice for routine cleaning/maintenance of mag heads, besides canned air?

Like all tape heads, I assume that occasional degaussing/demagnetizing is restorative? Is there a particular wand or nib tool that works well in the Century Mag heads?

I was eyeing these two options:
https://www.amazon.com/SaiDian-Degau.../dp/B0BD7Q2GKT

Or maybe:
https://reverb.com/item/51768884-rec...tizer-loc_ttl2

Without film in the path our CP200 has some pop and crackle that is noticeable in the rear channels anyway when you step outside the booth. Not sure if degaussing would help or if this is coming from elsewhere. (In our initial re-testing most of our stock is not long enough to really take a good listen outside the booth with film running).

[Jim Cassedy]

The first degausser in the Amazon link is more for demagnetizing large objects such
as CRT monitors and maybe you could use it to erase cassette & reel to reel tapes.
It's form-factor and size would be pretty impractical for use in the cramped quarters
of a mag sound penthouse!
> When I found out we were going to be running several old 70mm magnetic sound
prints before OPPENHEIMER last year, I bought a degausser on Amazon that looks
identical to the one in your second link.
> I found it was easier to get it closer to the heads if I removed the metal shields from
the JJ sound heads.
> Turn off your mag sound pre-amps when using the tool. Maybe I'm being over cautious,
but it will put out quite a large 60cy hum, at a level that may, or may not, be harmful to
your sound system. "Better safe than sorry" I say,
> On a professional audio website, I found some tape head cleaner and some sticks
that look like cotton swabs, but are some soft synthetic material that will not leave
cotton threads in your tape-head gap. (but I've also used regular long-stick cotton
swabs in the past with no problems. I mostly got used to using the synthetic swabs
when I was working with 1" videotape machines, where a cotton-clogged tape head
was almost fatal to the video head assembly)
> I'm not sure what's in 'real' tape head cleaner, but we often used 99% isopropol
alcohol on those 1" video heads, and I still keep some in the the booth for head
cleaning purposes. The important thing is to get 'pure' alcohol that doesn't have
any lanolin or other stuff that's sometimes put in 'cosmetic' alcohol .
> Stay away from acetone or carbon-tetrachloride. I've heard these can dissolve
some of the lacquers used on the tape-head windings & laminations.
> I was fortunate enough to have acquired over the years, a reel-full of 70mm mag
sound trailers, as well as a full 1k reel of pink noise. Keep your eyes open on e-bay
as these occasionally show up. They can be very useful for general testing, if you
can get your hands some.

I won't be at my theater till later today, to take a look at the degausser I bought, but
I went back and looked at my Amazon purchase history and THIS is the tape
degausserthingy I bought last year:


Degausser.jpg

Good Luck!

[Randy Stankey]

> I'm not sure what's in 'real' tape head cleaner, but we often used 99% isopropol
alcohol on those 1" video heads, and I still keep some in the the booth for head
cleaning purposes. The important thing is to get 'pure' alcohol that doesn't have
any lanolin or other stuff that's sometimes put in 'cosmetic' alcohol

The azeotropic point of iso. alcohol is 91%. You can't distill it to any higher percentage than that without using other, more complex, methods.

In other words, you can't buy pure alcohol in the grocery store and probably not at Home Depot, either. (Even if they say it's "pure" alcohol, it might not be.) Best to contact a chemical supplier to be sure you're getting the right stuff.

Also, alcohol can absorb water right out of the air. Once, opened, be sure to cap the container tightly to minimize the amount of water absorption. If you don't, that water goes onto the object you're cleaning and could, possibly, cause problems, later on. Especially with things like magnetic sound heads.

[Brad Miller]

Get yourself an Annis Han-D-Kit for the task.

https://www.rbannis.com/Han-D-Mags.html

[Jesse Crooks]

You can buy 99.9% alcohol from Amazon. No need to find a chemical supplier. It's often listed as electronics grade. I like using the pump dispensers marketed for nail polish and makeup removal.

For cotton swabs, the "precision" swabs sold for makeup application are my go-to for cleaning projectors. They are far less likely to leave fibers than a standard cotton swab (they have a firmer, denser weave) and come in shapes that are more practical for cleaning. They're available at any pharmacy. I buy so many projector cleaning supplies from the makeup aisle that I'm sure the cashiers think I have a fabulous night life.

[John Eickhof]

remember, its not just the heads that should be degaused ! take a small compass and check all sprockets, shoes, and metal pad or other rollers that are in close contact with the film as well as film trap and gate, I use a weller 50 watt soldering gun with two different coils to attach to it, one is a round coil of silid #12 awg insulated copper wire approx 6 turns and made so it will slip over a complete sprocket, you insert it over the sprocket, energize it and draw it out slowly and away from the sprocket 8 inches or more before de-energizing, you can make a rectagular form large enough to slip a film trap through or film pads, and the gate use approx 4 wraps of same size wire insulated. for the clusters, make a small coil of 40 turns of Ground Level insulated wire about 1/2" dia with 2" flex leads, place the end of the coil with a piece of tape over it against the cluster and slowly draw out andaway from the face of the cluster. always start with it de-energized, once at start point, energize and slwly draw coil out and at least 8" away from device before energizing. be careful with wand type degausers as not just heads clusters can get magnetized!

[Gordon McLeod]

This is what i use I made it from the specs in the 20th Century Fox handbook on Cinemascope demag.jpg

[Ryan Gallagher]

Thanks for all the suggestions folks.

Seems tool wise there are many ways to skin this magnetic cat.

I also found an older archive thread on the subject this morning as well, and yeah demagnetizing the whole film path seems advisable considering it's not been done since, well who knows when, and then check/redo it before 6 track engagements. Not sure compass hack would work for us with the giant cast iron Brenkert pedastals being so close by. But a more probe type meter might work.

I hate that gaussmeter prices basically doubled ever since ghost hunters decided they could use them to dupe people (or themselves). ;-)

I do have the cosmetic style swabs already. But only 91% iso in the booth. Will look into ordering the pure stuff for head cleaning, or settle for tape head cleaner fluids.

Late response cause had a full day humping a 4K Series 4 Laser (CP4420-RGB) and hush box to the upper balcony for a Netflix event with DTA. First 4K and DCI Laser that has been in our historic theatre, combined with the warp file generation via Mystique to fully correct our keystone, I have to say damn it looked good on the geometry front, even at our crazy steep angle. Projector envy. Rumor is we might score something along those lines during our architectural restoration that is always and forever "coming".

[Mark Gulbrandsen]

I used the same demag tool Brad has, as well as the Annus Magnetomer to test for residual magnetism. Both also worked fine on my dubbers back when I was doing a lot of location dailies. The major rollers on the MTM dubbers were made of 316 stainless, and were non magnetic. But from moving the dubbers around, the heads always needed a demag. Same on my integrated projectors that had the playback dubber built into the optical sound reproducer. BTW, you can buy direct from Annus or Amazon has some of their stuff available.

[Gordon McLeod]

As a side note I always disconnected the head when demagnatizing it

[Randy Stankey]

You can buy 99.9% alcohol from Amazon.

You can also buy it from supply houses like U-Line. My point was that you shouldn't buy off the shelf from the grocery store, pharmacy or home improvement store unless you are sure of what you are getting. When you buy from a supply house, you know what you are getting and you have product traceability that you probably don't get from buying in a store.

In a theater, traceability isn't a big concern but, in manufacturing, it's a big deal. If there is ever an issue, such as contamination, with the alcohol you buy, you need to be able to track down an isolate any of your affected goods. You can't do that so easily when you buy off the shelf.

You can use regular cotton swabs if you're careful. Wet them with alcohol then roll them between your fingers. That packs the fibers down so they don't come off on your work. Be sure to wear nitrile gloves. It keeps your fingers from contaminating the swab. Besides, you should be wearing gloves when using alcohol, anyhow. If you don't you'll get dry, "alligator skin" and your fingers and hands will peel. Especially when you are using the high test stuff. You don't have to ask me how I know.

[Ryan Gallagher]

This is what i use I made it from the specs in the 20th Century Fox handbook on cinemascope.

Looking into making one of those for drive sprockets to augment the tiny tape head degausser, I assume the coil has to be enameled or insulated wire. Hard to tell from your photos. And something like kapton tape to hold its shape.

[Mark Gulbrandsen]

remember, its not just the heads that should be degaused ! take a small compass and check all sprockets, shoes, and metal pad or other rollers that are in close contact with the film as well as film trap and gate, I use a weller 50 watt soldering gun with two different coils to attach to it, one is a round coil of silid #12 awg insulated copper wire approx 6 turns and made so it will slip over a complete sprocket, you insert it over the sprocket, energize it and draw it out slowly and away from the sprocket 8 inches or more before de-energizing, you can make a rectagular form large enough to slip a film trap through or film pads, and the gate use approx 4 wraps of same size wire insulated. for the clusters, make a small coil of 40 turns of Ground Level insulated wire about 1/2" dia with 2" flex leads, place the end of the coil with a piece of tape over it against the cluster and slowly draw out andaway from the face of the cluster. always start with it de-energized, once at start point, energize and slwly draw coil out and at least 8" away from device before energizing. be careful with wand type degausers as not just heads clusters can get magnetized!

John... The compass is a must, since all sprocket teeth are supposed to point North!

Also get an R.B. Annis pocket magnetometer to check other metal parts in the film path... There are other magnetometers available, but the Annis version is jeweled and can verify that nothing in the film path is magnetized.

[Ryan Gallagher]

John... The compass is a must, since all sprocket teeth are supposed to point North!

Also get an R.B. Annis pocket magnetometer to check other metal parts in the film path... There are other magnetometers available, but the Annis version is jeweled and can verify that nothing in the film path is magnetized.

I balked at those initially based on the "new" price, but there are a ton on ebay for reasonable, so will nab one. I ended up with one of the chinesium multitude of probe type gaussmeters on amazon. It was enough to confirm I had no grave magnetism concerns in the film path. But it does pick up some fractional milli tesla (mT) readings around the upper drive sprockets on both projectors, Hence the contemplating a tool to fully degauss those sprockets. The flux on my little tape-head degausser did not seem to have any effect on those parts/readings.

My kit so far:

VCC Universal Head Demagnetizer
https://www.amazon.com/dp/B003ZKLP4W...fed_asin_title

Handheld Digital Gauss Meter 0-2400mT (+/- 5% Advertised Accuracy)
https://www.amazon.com/dp/B0D25RPQXH...fed_asin_title

And one of these for fun (cause it was cheap):

Extech MD10 Non-contact Magnet Detector (Manufactured by FLIR)
https://www.amazon.com/dp/B00M9AX6AK...fed_asin_title

Annis pocket meter on the way (found one on ebay that still had the probe accessory). Hunting for the right price on ebay for a Weller D550 to mod for the coil style tool, though maybe the Annis Han-D-Mag is a more versatile and adequate as well if I can get a used one. But I like the idea of bending your own wire coils to fit different shape parts.

[Mark Gulbrandsen]

The Annis is powerful enough for most stuff you'll encounter. BTW, all teeth pointing north means no magnetism. JJ sprockets are also made of 316 stainless, which is the most non-magnetic steel made, but it can become paramagnetic from other magnetic particles.