[TenTec] Hercules II / 9420 high duty cycle

[NJ0IP]

Hi Ken,

I use my 9420 to power my Henry SS750HF.  It peaks 100A of current with
key-down.  I do not run the transceiver from the 9420 so I have all four
25-A power supplies available for running the amp.  Our mains here in
Germany are rated 234 vac.  They are highly stable at that voltage.

I ran CQWW CW contest (2004) using my Jupiter and the SS750HF.  My output
power was about 750w (our DL legal limit).  Worst case for me was a couple
of periods of about 2 hours of continuous CQ-ing.  During these periods, the
9420 got very warm - but I would NOT call it hot.  At any time it was
possible to grasp on to the heat sinks and hold them for as long as you
wanted without getting burned.

The 9420 sits on the floor behind the desk and is free for several feet in
all directions except towards the desk, where there is about 1 ft. of
clearance.

My SS750HF only has one 13.8v power connector.  It does NOT feed its 4 RF
power modules separately as the Herc II does (unfortunately).  To get around
this, I combine the 4 individual sources through 4 diodes.  To be exact, I
use 2 full-wave bridges, each rated about 50A and of course use only half of
each bridge (giving me two diodes per bridge).  I have small heat sinks
epoxied to the tops of the two bridges.  These heat sinks got so hot that I
could hardly touch them.  In the middle of the contest I wired up a 12v
boxer fan and pointed it towards the two bridges.  That helped a little.  

I am interested in replies that you get from others on this topic so if
anyone replies directly, please forward it to me.

Bottom Line: I find the 9420 to be an outstanding power supply for powering
transistorized linears.  The biggest weakness is its thin 13.8v power cables
and of course the molar plug (I think that's the name of those plugs).  I
plan to replace them with very thick cables and no plug, if I ever find the
time.

73
Rick

-----Original Message-----
From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com]
On Behalf Of Ken Brown
Sent: Sunday, February 20, 2005 5:46 PM
To: tentec at contesting.com
Subject: [TenTec] Hercules II / 9420 high duty cycle

Hi all,

I used my Hercules II and 9420 power supply in the ARRL DX contest this 
weekend. The amplifier worked great, never showing any signs of strain 
or overheating. The 9420 power supply got quite hot. It is powering only 
the Hercules II. I am using a separate 961 to power the Omni VI exciter. 
The specifications for the Hercules II says: Duty Cycle CW/RTTY - 50% 
duty cycle continuously. The specifications sheet for the 9420 says 
nothing about duty cycle. The power supply seemed to be getting too hot 
to continue, so I gave it a break. I used just my hand to feel the 
temperature, no instruments were used to measure the temperature. My 
9420 sits on the floor with two or three inches of clearance on all 
sides for air flow. I am running it from 240 VAC. Before I use it again 
for high duty cycle operation, I feel that I need to improve the cooling 
of the 9420, probably by adding a fan or two. I am interested to hear 
from anyone who has used the Hercules II and 9420 in a contest or other 
high duty cycle operation. Is my experience with the power supply 
heating typical? Has anyone mounted a fan on a 9420? I am thinking about 
fabricating a new top panel, since it is the simplest part of the 
chassis and has nothing mounted to it, and mounting a fan on it.

Thanks for any sage advice,

Ken N6KB


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