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Author Topic: Swan Mark 1 Amplifier Tube Cooling  (Read 4365 times)
KO4NR
Member

Posts: 182




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« on: August 12, 2003, 03:40:16 PM »

The Swan Mark 1 does not have provisions for the heat
to escape the amp through convection.  The internal
fan blows air across the tubes and it exits out the
back.  The underside of the top cover (has no
perforations) absorbs the heat and radiates it away
from the RF deck.  I am thinking I may cut a hole in
the top of the amp and cover it with a perforated
metal plate.  This will permit the heated air from the
tubes to escape faster.  Is this a good idea or did
Swan know what they were doing?  I am concerned
because the amp's top cover does get very
warm in operation.

73,
Bill

 
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WB2WIK
Member

Posts: 21832




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« Reply #1 on: August 12, 2003, 04:44:09 PM »

I wouldn't change the air flow in the Mark 1.

Swan knew what they were doing.  They used a large axial fan to draft air both above and below the chassis and exhaust it out the rear.  This is a good idea for a few reasons:

-It cools the filament pins (below the chassis), and filament pin overheating is a leading cause of tube failure.

-It drafts air horizontally around the tube envelope in a very efficient manner, providing all the cooling the tubes need, and at the same time drafting air across the finned plate caps, which keep the plate/glass seals cool enough.

-The design allows other equipment to be stacked on top of the amplifier, which could be a good thing in a crowded shack like mine!

Since the Mark 1 is very old now (they were built in the mid-1960's), you might think about servicing the cooling fan if you haven't already.  Keep the blades clean and dust-free, and occasionally oil (just a drop or two of lightweight oil) the motor bearing.

I rebuilt a Mark 1 some years ago to remote the power supply and put it in a separate chassis, which is what Swan did when they created its successor, the Mark 2.  That does keep the whole chassis, and its cover, quite a lot cooler...

WB2WIK/6
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