This is topic Degaussing for Mag Film in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=005835
Posted by Brad Morris (Member # 1175) on 02-08-2004, 03:51 AM:
Time to ask the pros.....
For those booths that run mag film, how often do you degauss the path and parts that come in contact with the film? What type of degausser do you use?
Thanks.
Posted by Floyd Justin Newton (Member # 1316) on 02-08-2004, 09:19 AM:
Brad--
I have found that degausing the ENTIRE film path with complete
thourghness is the best insurance in elemination of track "HISS"
and noise which CANNOT be removed once it is there. It would
take a couple minutes per machine and has to be done slowly.
fjn ![[Smile]](smile.gif)
Posted by John Walsh (Member # 168) on 02-08-2004, 09:21 AM:
We would carefully check and degauss for every print we ran; would check it every 2-3 weeks. It's been a long time I ran mag ![[Frown]](frown.gif)
but if I remember, I think you want a meter that reads 0 to 1 gauss. Of course, you want it to be as low as possible, but definitely less than 1.
To check, we used meters from:
http://www.rbannis.com/index.jsp
I only see one model (25); they used to make a smaller one which was easier to get into the shrouded area of most mag heads. Another manufacturer may still make smaller models. It also has a sort of 'extension' probe; it was a flat piece of spring steel the clipped to the bottom. They also make demag tools; 'buzzers' as we called them.
Once you have demaged the head, don't forget to do any screwdrivers or other tools you use to work on the projector.
Posted by Mark Gulbrandsen (Member # 72) on 02-08-2004, 09:29 AM:
There is a hand neld device called the Annis Magnetomiter that looks similar to a compass that can read the existance any magnitism in the film path. Its VERY sensitive capable of reading a maximum of plus or minus 5 gauss but ther eis one available as sensitive as .5 gauss! Its the only inexpensive, less than 100.00, device I know of that can verify the existance of magnetism or not. I also have one of their Han-D-Mags as well.
Their web site is here.....
http://www.rbannis.com
Mark @ CLACO
Looks like John and I were on the same page at the same time ![[thumbsup]](graemlins/thumbsup.gif)
Posted by Gordon McLeod (Member # 33) on 02-08-2004, 09:37 AM:
I use the guass meter daily and also ensure all your tools (screw drivers and allen wrenchs are degaussed as well also splicer and rewind spindles
Also if you use a platter all the roller spindles payout modules and even the screws that hold the platter decks on at one point a certain manufacturer used a magnetic screw gun to put in all there deck screws and every print on them got a tick tick tick added to the track
Posted by Mike Carro (Member # 232) on 02-10-2004, 10:06 AM:
I run 70mm. where do I get a Gauss meter?
Posted by Gordon McLeod (Member # 33) on 02-10-2004, 10:32 AM:
read the posts above as the link to the source is there
Posted by Sam D. Chavez (Member # 1841) on 02-10-2004, 10:41 AM:
RB Annis is the place. There used to be a Mr. Annis. Hopefully he is still around. I used to give the meters away at the Dolby training courses.
There are myriad ways to put clicks on the soundtrack or even erase it.
The original Christie cue detector used a magnetized pickup and relied on ferrous metal cues to trigger. I once ran a wonderful mag print of Dr. Zhivago that was moved over from the "good" house, and over my prostests, on one of these systems and as a test later took a reel back to the good house where the fader that used to run at 8 of 20 was now at 18 to get any sound at all.
Speco used to use magnets to hold the tail on the platter. When I pointed this out to one of the owners at a Showest years ago, he blew cigar smoke in my face.
I saw a tech work on the feed valve of a Christie platter using a Tensor lamp on top of the film for illumination. The subsequent thumps were amazing.
Posted by Gordon McLeod (Member # 33) on 02-10-2004, 10:50 AM:
"The subsequent thumps were amazing." I hope they had good subs ![[Big Grin]](biggrin.gif)
Posted by David Stambaugh (Member # 1102) on 02-10-2004, 11:38 AM:
One of the 70mm mag shows of "ET" that I saw was marred by a loud "tick - tick - tick" in the sound for about the first 15 minutes. Sure sounded like something magnetic came in contact with the print.
Posted by Brad Morris (Member # 1175) on 02-11-2004, 11:55 PM:
Thanks to all for the help. Now I just have to remember to take my watch off when using the degausser!
Posted by System Notices (Member # 2357) on 12-12-2005, 09:53 AM:
It has been 669 days since the last post.
Posted by Don Furr (Member # 1469) on 12-12-2005, 09:53 AM:
After having read all the replies in this thread and know where to get the gauge and the degaussing unit, but could some me a definite recommendation of exactly which degaussing model to purchase. I want one that I can wipe the entire film path through the projector without removing items and running them through a circular magnetic field. Also what about the head clusters themselves. Do you degauss the heads as well? If anyone is aware of a tutorial on the web explaining "how to do it" please let me know.
Don
Posted by Sam D. Chavez (Member # 1841) on 12-12-2005, 10:15 AM:
I do not have a specific model to tout.
The heads should always be degaussed (with the sound system off)particularly pre Teccon heads where the metal is very permeable.
If you a running platters, the screws that attach the decks to the frame are notorious for putting clicks on the film
Posted by Jim Latendorf (Member # 3425) on 12-12-2005, 11:33 AM:
"One of the 70mm mag shows of "ET" that I saw was marred by a loud "tick - tick - tick" in the sound for about the first 15 minutes. Sure sounded like something magnetic came in contact with the print."
I have heard this "tick-tick" sound when playing reel to reel audio tapes. Caused by static discharge from the tape being picked up by the playback head. Doesn't harm the tape, though.
Jim L.
Posted by John Walsh (Member # 168) on 12-13-2005, 08:11 AM:
You want the 'probe' type, rather than the round ones where the item must pass through. There were probably several manufacturers making demag units. Now that the general use of magnetic tape seems on the way out, many have dropped those products. Even Radio Shack didn't have the probe type listed on their web site.
It's really easy to do; just wave the meter everywhere the film goes, and attack as necessary! The extension probe for the meter is nice, too. You might be surprised how tough some screw or shaft is to demag, so keep checking.
Some projectors have their own special 'issues' like in a V8, where the magnet for the oil pickup is right next to the mag soundhead (it should be removed for the run.)
Posted by Don Furr (Member # 1469) on 12-13-2005, 01:39 PM:
Hi John....
I just purchased a kit from Annis. Thanks!
Don
[ 12-13-2005, 04:18 PM: Message edited by: Don Furr ]