Sam,
Gord once took me to a Kosher Deli in Toronto somewhere. Great place and they definately had insulted wire and great Kosher pickles to go woth it ![[Smile]](smile.gif)
.
Don,
The 1600's may work out better as they are either a straight high reactance unit or if its the older version just a bunch of pass transistors on a big heat sink. You still risk the possibility of induced hum and of rf being radiated from the arc, but these lamps always tended to be alot quieter with mag than the 1000's scr regualtor circuit ever was. Hope you get it wrung out, mag is alot of fun!
Mark
Posted by Frank Angel (Member # 248) on 04-15-2005, 11:53 PM:
Did I ever tell you about the time I was trying to get the change-over THUMP out of my mag system and I did everything I could think of to eliminate it but to no avail. I pinned it down to the change-over zipper coils as being the cuplrit. They were radiating that 60hz magnetic field right into the penthouse. I was getting really frustrated trying to figure out a way to stop it. Finally I decided I had to do something drastic.
I went to search for a supply of lead so I could make a lead shield to wrap around the penthouse and the zipper unit. I found a supplier but he would only sell me this huge bulk roll of lead weighing in at 100lbs. It was very thick, malleable stuff that I could mold around the change-over unit and the back portion of the penthouse. OK, so I had to buy a lot of it; who cares since it was going to stop that hum in its tracks.
I was every proud of my handiwork, lead wrapped around anything that didn't move. Even though it didn't look very pretty and I probably absorbed lots of lead in the process, I was convinced this was going to do the trick. Then came the test only to find, to my great dismay and utter disappointment, that the thump was still there, audible as ever. I was truly bewildered. I mean, I covered every inch of the casing of the coils and thoroughly covered the penthouse with a few layers of lead. I even glued a layer on the door.
You know that feeling you get when you work on a problem for hours and hours and at the end it just laughs at you? It's not a fun feeling. I gave up and left the booth and found one of the older techs in the sound studio and poured out this story to him over a beer. Throughout my lament, he looked at me with this perplexed and awed expression. When I was done explaining how the 60hz hum was still able to get through the shield I had fabricated, he ask in a slow, deliberate voice, "So what made you think that lead will stop a 60hz AC induced hum field? I thought for a minute, and couldn't really come up with anything other than, "Well, EVERYONE knows that lead stops all kinds of radiation." He just smiled and said, "Frankie, you are thinking of Superman's X-ray vision....Superman can't see through lead because it blocks his X-Ray vision; it has no effect on AC hum fields." I was stunned. And quite terribly humbled.
The huge roll of unused lead hung around the back stage area for months only to prolong my pain.
In my defense, I was only 22 yrs old.
If you heard my story before, I apologize, but it still is a good lesson of what can happen when you make assumptions while troubleshooting.
Posted by Sam D. Chavez (Member # 1841) on 04-16-2005, 12:19 AM:
That's why they call it cut and paste. You try something and then test it, but you should not wait till showtime.
There is a metal that does block these frequencies.
It's called mu metal. Perm-alloy works also.
There is a piece of mu metal on the back of the JJ Zipper douser.
Works wonders. The heads on the this penthouse should have mu metal shield.
Posted by Steve Guttag (Member # 268) on 04-16-2005, 07:31 AM:
Yeah, most people don't get the Mu-metal thing. They seem to think they are dust shields or something. Simplex's 35/70 forgot completely about the mu-metal shields in the 80s (don't know about the originals).
A way of dealing with the hum at changeover time is to eliminate the hum...that is...run your changeovers "DC". Ever noticed that Essanay offers DC coils? I've done this several times. However, things that may have worked okay in AC may fail in DC...check the rating of your switches/relays before making the switch. You will often have to make your own power supply too (needn't be anything fancy).
Posted by System Notices (Member # 2357) on 11-29-2012, 03:00 PM:
It has been 2784 days since the last post.
Posted by Jason Metcalfe (Member # 5739) on 11-29-2012, 03:00 PM:
Hey Don, I wanted to see if you ever found a solution that worked for you, we're getting a really bad hum from the lamphouse when playing mag track 70mm though our JJ, or at least it's only present when the lamp is struck.
Posted by Ben Wales (Member # 92) on 11-29-2012, 03:55 PM:
I had the same problem at home with my ORC/Orcon 1000B and the only way I could remove the Earth Hum was to ground a wire direct to Sound rack and the Projector.
Posted by Don Furr (Member # 1469) on 11-29-2012, 04:24 PM:
Jason that's been so long ago I really don't remembered what I did to resolve the problem.
All I can tell you is that I'm still running mag but using a Strong Super LumeX lamp and I don't have any problem with hum.
![[thumbsup]](graemlins/thumbsup.gif)