[Amps] Drake L-4B fan - too small and too slow?

[Phil Clements]

> Second question: why did Drake only fit a 2.5 inch 1550 rpm blower, when
> Eimac suggest a 3 inch 3100 rpm unit? The Drake unit is made even more
> puny by our 50Hz mains supply, which just compounds the problem.

Alan, for years, the amp makers have been giving in to the customers that
want a big amp to sit right on the table in front of them, but they will not
tolerate even the slightest blower noise. You can't have it both ways; when
the 1 kw input limit was lifted, that put us in another category of need for
adequate airflow. I agree that your problem is compounded with your 50 hz
mains, but I am sure that with over 1 kw input power that the old small
blower is not up to the task. Large commercial and industrial amps have
always had the 3600 rpm blowers for good reason; to keep the temperature
within factory specs on the tube(s) and components. In the past 25 years,
manufactures for the ham market have put in larger tubes, more robust power
supplies, smaller blowers, and smaller tank components; obviously catering
to the buyer's demands to have a cheap big signal with no noise.
As we say in Texas, that dog won't hunt. (for long)

Surely someone has come up with a replacement solution for the Drake.
Perhaps you will hear from them.

(((73)))
Phil Clements,
K5PC