[TenTec] Hercules II fan noise

[Duane Calvin]

Re: thermal engineering at TT - - Clearly not their forte, Steve, nor is
acoustics (your fan is an example, as was the Centaur amp).  Back to the
thermal side, check the heat sinks on the power module on the Orion (and the
Omni VI+ and probably others) - - the fins are mounted horizontally.  Seems
to me you would want to aid convection and orient them vertically.  But,
hey, I'm just a EE with a semester of thermodynamics and fluid mechanics,
not an ME!  (hi!)

	73, Duane

Duane Calvin, AC5AA
Austin, Texas
www.ac5aa.com  
 
-----Original Message-----
From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com]
On Behalf Of Steve Hunt
Sent: Wednesday, August 27, 2008 10:56 AM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Hercules II fan noise

Today I did a few checks on the present fan.

1) I unbolted it from the under-tray and held it in place by hand. There 
was no reduction in noise, so I don't think resilient mountings will help.

2) I removed the fan completely and ran it on the bench from an external 
PSU. It was a little quieter, but not by much.

3) I tried a small amount of lubrication but that made no difference.

4) One thing that made a surprising difference was the presence or 
absence of the "finger guard". In fact anything close to the fan and in 
the intake airflow made quite a difference to the noise level. Just 
holding a pencil across the intake brought the level up noticeably.

5) Surprisingly there was very little dust around the fan or the heatsinks.

I've managed to locate a new fan that seems to have an equivalent spec - 
it should be here in a few days, and hopefully will solve the problem.

I wasn't too impressed by Ten Tec's thermal engineering. The fan is on 
the underside of a central chassis plate, and the PA transistor heat 
sinks are the other side. There are just a couple of very small holes in 
the plate where the air can flow from the fan side through to the 
heatsink side!

73,
Steve G3TXQ



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