Hi Hank,
As a new owner of a 5 year old Centurion amp, I am curious to know the age
of your amp ? I am running the Centurion with my Omni 6 Plus and have not
seen either of the problems you encountered. However, I have lots of coax
running around the amp and between the exciter, etc.
73 and look forward to hearing from you. Glad to know that TenTec and the
list here were able to help solve your problem.
73,
Dave, K2DP, St. Louis
----- Original Message -----
From: "Henry Pfizenmayer" <pfizenmayer@worldnet.att.net>
To: <tentec@contesting.com>
Sent: Monday, October 10, 2005 10:11 PM
Subject: Re: [TenTec] Centurion Squeal and Oscillation
FWIW _ It appears with the help of several folks on this reflector and the
AMPS reflector the Centurion oscillation problem on 40 meters is resolved.
It also appears the "squeal " is fixed but may require a little more time
to be 100 percent sure.
Tentec service says the squeal is coming from the fan bearings and
recommends you take the label off the fan and tighten the screws behind
the label . This is a weird one as the pitch does not change when you turn
off the amp and the fan is running down - my fan spins for about 74
seconds after turn off- TT says the one they timed was more like 3
minutes, so I may have marginal bearings. This operation is a little bit
of a pain as the fan label and screws are right behind the RFC and
parasitic suppressor assy, so you have to remove the tubes and the rfc
assy to get to the fan.
The solution for the oscillation on 40 meters was to increase the length
of coax between the Orion and the Centurion. One person also suggested a
W2DU type ferrite bead current mode "isolator". I had a Wireman balun good
to 160 so I tried that (that added about 3 feet to my already 4 foot long
jumper) and the oscillation stopped, and all bands were stable.
I wondered if maybe the real change was just the extra cable length so I
made up a 8 foot RG8x jumper and the amp was still stable all bands. When
I called Tentec to tell them about the solution - they said they normally
use about a 8 foot cable so they had never seen what I encountered with a
short interconnect.
So In summation.
Squeal - Tighten the screws under the label on the fan
40 meter oscillation - be sure you have at least 8 feet of RG8 or RG8X
cable between the exciter and the. amp
Thanks to all for the suggestions - looks like I am back in business.
Hank K7HP
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