[Amps] 8877 blower requirement ?

[Bob Alexander]

Hugh,
The 4C440 only has 60 CFM at 0 static pressure... an 8877 needs around 40
cfm at .6" SP. and the 4c440 does not meet this spec.
I do not know the specs on the 2C610  but it is probably around 70CFM at .6
SP so it would be
the best choice of the two....even though noisier.
73, Bob W5AH

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]On
Behalf Of Hugh Duff
Sent: Thursday, April 05, 2007 6:51 AM
To: amps at contesting.com
Subject: [Amps] 8877 blower requirement ?


I have just about finished building a W6PO style 8877 amplifier for 2
metres and I now need to install a blower. I have a 2C610 (140 CFM)  and
a 4C440 (60 CFM) and I'm wondering which one, if either, would be
suitable. The latter would be desireable for lower noise but I want to
make sure the tube is sufficiently cooled without overdoing it.  The
Eimac datasheet that I have simply states "Cooling: Forced Air" with no
CFM airflow specified.

I've seen rogue statements to the effect of "the bigger (more CFM) the
better" but according to the Econco "Tube Maintenance" document, too
much cooling may affect the electron emission of the filament.

So I'm curious to know what the optimum CFM requirement is to
sufficiently cool a single 3CX1500a7.


73 de Hugh VA3TO
www.va3to.com


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