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SERVICE BULLETIN
January 29, 2009
The K4 is a powerful 300-Watt compact and light-weight combo
amplifier for keyboards. The product houses 5 drivers in it's speak-
er section and a chassis that has 3 amplifiers, a set of tubes, 2
fans (with heat sinks) and 6 circuit boards. All of these compo-
nents potentially rattle and/or buzz at various frequencies. Yorkville
uses a specific method to help prevent the sound energy from
being transferred from to the speaker compartment to the chassis.
Yorkville has taken great care by using dampening foam inside
to help reduce a great deal of rattling. Special foam and rubber
washers are also used for mounting the chassis to the cabinet.
The top 5 chassis mounting bolts are not fully tightened, this helps
prevent the transference of the sound energy to the chassis from
the speakers.
Over tightening the top 5 bolts may result in rattle and buzz!
If chassis is removed and replaced, we recommend using a
Phillips head screw driver and tighten each bolt so that the top of
the head is just above the surface of the cabinet. To test if the
mounting is done correctly, apply a little force to the front and then
the back of the chassis if it moves too much, retighten the bolts
and redo the test again.
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