On 11/13/2011 9:21 AM, Ignoramus22978 wrote:
Here's a picture.

http://boss-proxy.chudov.com/tmp/tmp-0432.jpg.html

That amount of surface rust and corrosion INSIDE a cover
indicates it's been wet, or in a wet location.

That's a disc brake and should dis-engage when the hoist
is in operation.

Do you have the wiring diagram for this hoist?

I know that label reads, "Caution dual voltage" as an
indication it "might be wired for a different voltage than
what you're using.

Despite all the random guessing, I'm assuming that is a
very simple straight forward coil that pulls the release
on the disc brake.

If that coil is set up for 480 volts and you're putting 240
across it, it IS going to buzz and chatter. It will do that
without any missing diodes, open coils, hidden switches or
two sets pull & hold windings.

If that coil is set up for "dual voltage" it should have
more that two wires connecting to it. Or there should be a
control transformer somewhere else in the housing to supply
the correct voltage to a single voltage coil. Or a dropping
resistor (not likely) to allow a 240 coil to be used on 480.
And the instructions, as such, should have the connection
for both voltages and everything you have to reconnect listed.

Jeff

--
"Everything from Crackers to Coffins"