I might suggest a bead of GE silicone sealer (next time) to act as both a
noise dampener and a air seal.
73,
Gary...wa6fgi
----- Original Message -----
From: "Alan Ibbetson" <alan@g3xaq.demon.co.uk>
To: <amps@contesting.com>
Sent: Tuesday, February 14, 2006 2:49 PM
Subject: [Amps] Drake L-4B fan replaced with Dayton 4C761
> Late last year I was complaining that the fan in my L-4B was not keeping
> the valves within their temperature rating with 50Hz mains, especially
> on CW at full power. Jason N1SU suggested that I replace the stock fan
> with a Dayton 4C761. I finally got one of these units brought over to
> the UK by a work colleague.
>
> I just wanted to report that the fan is pretty much a straight swap. I
> had to saw and grind off the exit flange on the blower and extend the
> through hole in the chassis to accept the bigger outlet. The intake does
> not quite line up with the original hole on the rear panel of the
> amplifier because the new blower is slightly bigger. The error is not
> large - the escutcheon fits OK without fouling - and anyway it's out of
> sight at the rear of the case.
>
> I used 1.5mm felt from a craft store as a sound deadening gasket at all
> points where the blower meets the chassis. Even so, the Dayton blower is
> noticeably noisy, as Vic K2VCO predicted. I find it acceptable, because
> I operate mostly on CW with headphones. On SSB, with the speech
> processor turned on and the L-4B 18 inches from me, the fan noise drives
> my transceiver to about 10% output. It would be even worse on 60Hz mains
> unless steps were taken to slow the fan motor down. Much of the noise is
> coming from the impeller and a clip-on external dust filter of the type
> sold for muffin fans might be worth investigating.
>
> Has it fixed the overheating problem? Oh yes, definitely. I can feel a
> healthy breeze from the top of the cabinet and the case is now only
> comfortably warm to the touch at the end of a long transmission.
>
> I have photos I can share with anyone who is contemplating this mod.
>
> Thanks to everyone for their suggestions and encouragement. I'm very
> happy with the outcome.
>
> --
>
> Cheers,
>
> Alan G3XAQ
> alan@g3xaq.demon.co.uk
>
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>
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