Try an EBM/Papst Pamotor Model 4600X. Its 4 5/8" square, all metal,and
provies enough air to almost send the three 3CX800's in an LK-800 into
orbit.
Carl
KM1H
----- Original Message -----
From: "Robert Briggs" <vk3zl@bigpond.com>
To: <amps@contesting.com>
Sent: Thursday, November 25, 2010 5:19 AM
Subject: [Amps] Tube Cooling
>
> I am experimenting with a new 2 x GI-7B amplifier using muffin fan types
> to establish whether I can get reasonable air flow...Test 1 was using a
> pair of 240 volt 3.5 inch fans mounted beneath the tubes blowing over
> the cathodes exiting through chimneys and out the top of the
> amplifier...Result is pretty dismal..Muffin fans don't like restricted
> air flow...
>
> Experiment 2 was mounting a pair of the fans above the tubes sucking the
> air through the coolers...At first I thought the flow wasn't much better
> but discovered that the exiting air is thrown radially rather than
> straight upwards...Of course as there is no concentration of the output
> upwards one can only guess how effective the flow is...
>
> Tomorrow, I am going to add a pair of 12 volt 3 inch muffin fans under
> the base plate cathode compartment and try a push pull effect with the
> 240 volt fans on top..If this improves the flow I will then replace the
> two top 240 volt fans with a more powerful single 5 inch muffin
> fan...The fans certainly run quieter than any blower I have
> tried....Suitable blowers are virtually unobtainable in VK and have to
> be sourced overseas which with shipping make them very expensive..
>
> I figure that in service running 700 watts ssb output, dissipation would
> not be greater than 400 watts of heat from 2 tubes all up but this is
> just a generalisation on my part...I don't have a means to actually
> measure anode heat..
>
> Running data modes for meteor scatter etc would probably strain the
> friendship past 300 watts output in 30 second bursts but worth looking
> at..
>
> I would be interested in other opinions..
>
> Bob..VK3ZL..
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