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Topic: Buzzing Lamphouses

Joe Redifer
You need a beating today

Posts: 12859
From: Denver, Colorado
Registered: May 99

posted 10-05-1999 05:26 AM

I have 2 Christie SLC40-2 lamphouses that have developed an extremely annoying buzzzzzz. It is far from normal. In fact, the buzzing is so loud that it can be heard in the auditorium, and we have pretty good insulation. The buzz is coming from the power supply. Bulb operation and life seems unaffected.

I e-mailed Christie about it and I don't think they know what is going on, either. Does anybody have any advice on what I could try to eliminate this?

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John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 10-05-1999 09:46 AM

Maybe it's the transformer- I assume it's not
a switching type power supply.
Some AC to DC power supplies have a procedure
that aligns and tightens the laminations(sp?)
in the transformer, or the group of three,
as in power supplies for 3 phase.
If it is a switching supply, I think
something is seriously wrong.

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Ken Layton
Phenomenal Film Handler

Posts: 1452
From: Olympia, Wash. USA
Registered: Sep 1999

posted 10-05-1999 10:30 AM

Could be the contactor. Also check for loose hardware on the transformer and any cooling fans, too.

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Rick Long
Jedi Master Film Handler

Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999

posted 10-05-1999 05:14 PM

You've probably already tried this, but try placing your hand on the power supply cover. If the hum lessens condiderably, try foam weather-stripping between the cover and the main body of the unit.
You can also try foam isolation between the power supply and the floor of the console, or, if outside the console, between the power supply and the floor.
As you probably know, using an insulated stick (such as a short broom handle) against your ear can help to isolate the part that is humming.
P.S. Are all three phases present? Some switchers will work fine on just two live input lines.
Just my two cents worth. (Of course with the Canadian dollar being what it is, that amount to about a cent and a third).

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Joe Redifer
You need a beating today

Posts: 12859
From: Denver, Colorado
Registered: May 99

posted 10-05-1999 07:12 PM

Here's what Mr. Sean T. James of Christie Inc has to say about the situation:

Joe,

The noise that you are hearing is usually a indication that the resin that
is used to varnish the transformer is allowing one or more of the coils to
move. Under power, the vibration of the coils can be enough to produce quite
a bit of noise. There are two ways to resolve the problem. If the coils in
the transformer which are buzzing can be identified, wood shims can be
tapped in between the shunts in the transformer and the core of the
transformer which can sometimes alleviate the problem. If the location of
the noisy shunts and coils can not be found, the power supply would have to
be replaced. As always ensure that all power has been removed from the
equipment prior to making your inspection. Please keep me informed.

Joe here: I think that I'll try wedging that peice of wood between each coil and see what happens. If this doesn't work, then the problem is probably pretty serious.

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Tim Reed
Better Projection Pays

Posts: 5246
From: Northampton, PA
Registered: Sep 1999

posted 10-10-1999 02:59 PM

I had this problem in a National Amusements theatre, which was then about 15 years old. The wood shims worked.

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